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Hydrogen Properties for Energy Research (HYPER) Lab Service

Orbital TIG Welding – How HYPER strives for the best welds!

Sealing anything at cryogenic temperatures requires extremely tight tolerances. If tight tolerances are not considered, holes may open at the source of the seal, allowing cold leaks to occur as referenced in this past post. In today’s How To, we’re going to discuss how to weld tubes together utilizing orbital TIG welding. Orbital welding has given the lab an advantage in that all our welds minimize human error and the whole operation is computer automated. The system being used is Swagelok’s M200 orbital welding system, which was donated to our lab through the Boeing Cybergrant program. The procedure is as follows:


The first step to perform a tube weld is to prepare the two ends of the tube that will be joined together. For this example, we will be welding a .5in 316L stainless steel tube.

  1. To ensure a flat contact between the two tubes both ends must be chamfered using a Metabo drill with a carbide cutting tool.

To Chamfer the tube face, insert the .5 in collet into the end of the drill.

Then insert the tube into the drill and while holding the red trigger slowly turn the blue nob to cut away the end of the tube to a flat surface. Once the desired amount of material is cut back off the bit from surface of tube before releasing red nob to ensure no build up is left on the face of the tube.

Next use the blue handheld chamfer tool to remove any burs from the inside and outside edge of the tube.

  2. Now that the tubes are ready to be welded it is time to set up the Swagelok M200 power supply.

First, perform a visual inspection of the M200 power supply and ensure that it is plugged into a wall outlet and the Argon bottle is connected to the power supply.

Then make sure that the weld head is connected to the Power supply like so.

To program a new weld, begin by flipping on the machine using the on/off switch on the upper left side of the M200. Once powered on you should see a page like this. Select the “Program” key from the main menu then Auto weld and select yes to the warning.


Enter the parameters as shown, You may need to use calipers to measure pipe diameter and wall thickness.

Next, once the program is entered with specific parameters the following operating screen will appear.


Since the tube is 0.5 in., the Arc Gap must be set as to allow the tungsten rod to make accurate contact with the tubing. To do this, the height of the arc gauge must be set to a specific height listed in the program under arc gauge. In this case, the height is 0.922 inches.

4. To insert the tungsten rod into the weld head first hit the electrode change button on the screen. This should move the electrode to the top position. Note: different weld jobs may require different types of electrodes. the process page has a table which tells you what electrode is needed for the specific job. For this case, it is electrode c.040-.555. The electrodes come in small bags that should be labeled.

Next, place the arc gauge into the weld head where the tungsten rod is located. From there, loosen the top two bolts so that the tungsten rod can move freely. After, allow the rod to fall into the divot on the arc gauge. This will properly set the rod for welding. Finally, re-tighten the bolts and remove the gauge.

5. To prevent contamination from the air a positive pressure of argon must be flowing through the tubes while the weld is taking place. To accomplish this attach the clear tube coming from the green ball valve to the side of the tube that was not faced using a compression adaptor. To ensure back pressure, connect the other tube to the compression adapter with black tape on the end.

6. Now the tubes are ready to be inserted into the fixture device that holds the tubes in place.

Insert the tube connected to the valve into the left side of the clamp and use the attached spacer to ensure the tube is centered in the clamp and secure it so it does not move.

Then insert the other tube into the right side of the clamp and secure.


7.  Finally, insert the weld held into the fixture and turn the tab on the top to secure it the clamp.

8. Now we are ready to perform the weld.

Start the weld by turning the green valve to start the flow of argon through the tubes, then hit the “Shield gas” button on the control panel to flow argon around the outside of the weld. Next hit the green “Start Button” on the bottom of the screen. The system will conduct a gas purge before welding as well as a post-purging. This ensures that there is no oxygen in the system before and after welding. The screen should look something like this.

9. Remove the weld head to inspect the weld and turn the green valve off before removing the welded tube.

If the weld goes correctly and all pieces were set correctly, then you should have a beautiful weld as shown below. Congrats!

If you’ve done this right, the quality of the orbital TIG welds maintains the ductility of the base material and you should be able to fully bend the weld without cracking or breakage. Happy welding!

Isaiah Bells with a quality orbital TIG weld on 1/4″ SS316 tubing.


Cold Saw Use Did You Know

Cold saw cuts in  a material are more similar to a milling operation than those of a traditional abrasive saw. Cold saw blades rotate much slower that an abrasive saw and combined with the continuous flow of coolant the cuts produced are much quality in terms of surface finish and accuracy. For a full user manual for our specific machine please see here. Before any cuts are made, the saw should be momentarily started without contacting any material to ensure that the blade and rotation are both in the correct direction and no blade wobble is experienced.

Securing Materials

Possibly the most important consideration to avoid injury and poor cut finish is properly securing the material to be cut. If a piece of metal or wood is not properly secured in the cold saw there may be unwanted vibration and flexing of the work piece. If there are vibrations during cutting, the cut surface will end up looking much worse than otherwise as well as the cut being less accurate than a cut that is properly secured. If the material is allowed to flex during cutting you may experience binding on the blade. This will cause a poor cut quality and unnecessary heat production in soft materials like aluminum, and in harder materials like steel you may experience a broken blade or chipped teeth. Another situation that may be experienced is the end of the desired work piece not contacting the back of the vice on both sides of the blade because one end of the work piece is too short. In this case, a sacrificial piece of material may be inserted below the working piece that does contact both sides of the vice. This will provide some support to the working material and help prevent some undesirable vibrations.


Before any process is started with a cold saw, the blade should be started for a moment to assure that everything is in working order. One check to make at this time is that there is coolant flowing while the blade is rotating. If there is no coolant flow, there are a couple simple checks to make that may remedy this. The first place to look for a solution is the ball valve directly behind the blade cover. If this valve is closed, then there will be no coolant flow. If this valve is open and still no coolant flow, then the issue may be with the supply hose or the coolant tank directly below the saw. The coolant tank should have a mesh filter in the top that will allows the operator to check the fluid level. If this fluid level is not high enough to show in the mesh filter due to either evaporation or splashing during saw use, then the tank needs to be filled. The concentrated coolant is stored in the chemical cabinet and should be mixed with water at a 20:1 ratio by volume. Enough should be mixed to fill the tank until the mesh screen is at a maximum level. The large coolant supply hose should be present and in the mesh filter below the coolant level.

Upright Mill Use Did You Know

Is machine use necessary for this project?

  • Precision cutting required
  • Precision hole placement
  • Bulk material cut to a complex geometry geometry
  • Material constraint on fabrication type


Machine Controls and Table Movement

At first glance, the leavers and knobs on the mill head may seem intimidating. For most general operations though few of the controls are used making the learning process much easier. Most projects can be taken care of by using the table X, Y and Z feeds along with the quill feed handle.  Eventually there will be processes that require you to learn more of the ins and outs of the machine such as head tilting or changing the mill speed. The X and Y axes movement are controlled by the two round handles connected to the base of the machine. When the X axis is referred to, the side to side travel is being referenced while the Y axis feed refers the movement of the table to and away from the user. If the table X axis of our machine is locked in place and the handle won’t turn, the culprit is likely the X axis auto feed being engaged and can be solved by disengaging the auto feed. For a video showing some basics of the machine controls please see here.

Collets and Drill Chuck

The cutting tool to be used will be held by either a collet or a drill chuck. A drill chuck is useful when you need to drill multiple holes of multiple sizes because this attachment allows you to quickly change between drill bits without changing the chuck itself. It should be noted that the chuck is meant specifically vertical holes and is never meant to be used when horizontally feeding the work piece. This is because drill chucks are meant for vertical forces but not necessarily for horizontal forces. Our drill chuck is mounted to a Jacob’s taper, this taper mount has a threaded top to attach to the quill and a tapered base that creates a friction fit with the drill chuck. Excessive work piece vibration can cause the friction fit to loosen causing the drill chuck to fall off the taper mount. If this does happen, the drill chuck must be remounted to the taper. Both surfaces should be cleaned first with a solvent such as acetone to remove any oils present that may otherwise act as a lubricant in this fit. To secure the two pieces, the top of the Jacob’s chuck should be struck onto a piece of wood that backed by a solid surface.

Collets are designed to be used with a specific cutting tool shank diameter allowing a much more secure fit than a drill chuck. Both endmill bits as well as drill bits are usable with the appropriately sized collet allowing for either drilling or horizontally fed workpieces. To mount a collet and endmill, the collet should be tightened onto the quill loosely at first without the endmill inserted. After the collet is loosely connected to the quill the endmill should then be inserted so that the cutting surface is fully outside of the collet while being supported by your hand to prevent dropping the endmill onto the mill bed. The quill is then hand tightened until the mill bit will no longer drop out, and at this point the spindle brake can be used to allow the quill to be tightened completely with the wrench stored on the machine. For a simple video showing this process and some information on mounting types see here.

Cutting Fluid and Lubricants

When available, appropriate cutting fluid should always be used on the piece to be cut. Cutting fluid when working with steels will primarily act as a coolant for the workpiece and cutting tool, cutting fluid while working with aluminum will work the same as with steel as well as preventing metal from gumming up the cutting tool. This is because Aluminum is soft and will stick to the cutting surface of the tool effectively dulling it. A dull tool cutting surface will cause higher heat, poor surface finish along with increased vibrations. For our uses, a couple drops of lubricant per inch will generally provide enough lubrication for small projects. For a quick reverence chart comparing material type, process and cutting fluid type see here.

General Endmill Cutting Tips

The cutting tools that we currently have in the TFRB are all square end titanium nitride coated bits in two and four flute styles. Higher flute counts are generally used with harder materials, so if stainless steel needs to be cut then a four-flute bit should be used while a two-flute bit can be used for Aluminum. The cutting procedures can in general be broken down into slot/face milling, side milling and basic drilling. For side milling or face milling operations that do not use the entire width of the of the cutter the material should be fed against the rotation of the cutter also known as conventional milling. Climb milling will reduce the lifetime of the tool as well as potentially causing backlash in the machine. Backlash can cause the cutting bit to bind up and break either the tool or the mounting setup. “How deep should I cut?” comes up often and the answer is “it depends”. The depth of cut that should be made varies based on multiple factors such as tool diameter, machine power, material type and feed speed. In general, it is recommended that the depth of cut into aluminum is kept to less than half of the diameter of the end-mill, and even shallower for harder materials like steel. When in doubt it is always safe to take a shallower cut with more passes. A shallow cut may require more time due to more passes being required, but this also requires less power from the machine and reduces the heat load on the end-mill bit.

Conventional milling diagram showing correct material feed direction.


When side milling, as much of the cutting surface should be used as possible giving as deep of a cut as possible. The best situation is to have the cutting surface cover the entire side depth to be cut so that there is no material being cut by the base of the end-mill. The attached photo shows an example of the “correct” way to side mill as opposed to the less efficient side milling setup.

Typical setup for a side milling operation with desirable depth of cut.


Drilling holes with a mill is also an option that can be performed with either a drill bit or an end-mill that is designed to be able to plunge. End-mills can plunge into the material if there are cutting surfaces in the center that are designed to cut down, but if the bit is lacking this center cutting surface then plunging may damage the bit. Because of this potential damage, it is recommended to use a drill bit when drilling into a work-piece. For a more in depth look at end mill types and general use recommendations see here.


For aditional reading material that explains each of the concepts mentioned here please refer to American Machine tool’s web page “INSTRUCTIONS HOW TO USE A MILLING MACHINE

There are also many video tutorials available online for manual mill use that cover everything ranging from the basic use to very specific use cases. A relatively simple tutorial that should give a solid base to get started is attached to this page.

CLEAN Workbench Assembly

In the Fall of 2016 ME seniors Ryan Pitzer, Jake Enslow, and Austin Rapp designed the CLEAN (Cougar Lean) workbench. The CLEAN workbench is designed to maximize organization and accessibility in the work-space. These benches can easily be attached together to create a larger work-space, which can be largely beneficial in any research lab. This is an improvement from the work-benches previously found in the HYPER lab; while they were functional as a work-space, they did not have the practical modular features that the CLEAN workbenches include.



Old work-benches in the HYPER Lab provided a functional work-space, but were bulky, heavy, and lacked the modularity to properly implement all of our tools. New CLEAN work-bench (right) used during initial N2 cooling tests in the HYPER lab!







  • Chop saw
  • Aluminum chop saw blade
  • Cordless drill
  • Drill bits: (43/64″), (7/16″)
  • 8mm Allen wrench
  • Drill Press, DVR preferred
  • Phillips Screwdriver
  • Adjustable wrench
  • Rubber Mallet
  • Clamps
  • M12 x 1.75 tap



1. After ensuring that the chop saw has the aluminum cutting blade properly installed, and the tubes are properly clamped in place, cut the Bosch tubes in accordance to the following cut list:


2. Lay the maple top upside-down on the work surface and use the cordless drill with the (43/64″) bit to cut holes for the Horizontal Quick Connect barrels. Drill in a pattern shown below:

The center of the holes are to be marked 22.5 mm in from the side edges of the block. This ensures that the T-bolt notch for the Quick Connect is within tolerance.

The illustration above shows how a Quick Connect piece can clamp Bosch tubing up against the maple top. Above the notch rests a screw which pulls the head of the T-bolt in closer towards the barrel as it is tightened down.



3. In order for the Quick Connect assembly to work, a (7/16″) wide hole must be drilled on the side of the maple top perpendicular to the previously cut holes. This allows for the T-bolt to slide into the side of the barrel component of the Quick Connect.



4. Drop the barrel component of the quick connect piece into the maple block with the threaded side up. Then insert the T-bolt into the side of the maple block, and into the barrel. The notch on the T-bolt must be visible inside of the barrel. Slide the T-Bolt in to the point where the rubber seal is flush with the maple block. Next, slide pieces D1 and D2 on either side of the maple block, while the T-bolts are threaded through the Bosch tube. Tighten using the 8 mm Allen wrench.

The method we use here to connect the Bosch tubes to the maple block leaves a clean, seamless finish on the surface of the workbench.


5. Collect parts B1, B2, C1, E1, and E2. Prep the drill press with the (43/64″) drill bit. On each of the listed pieces, use a Sharpie pen and draw a dot marked 22.5 mm away from the edge of the tube. Repeat this process once for each tube so that one face of each tube is marked twice, once on each end. Align the drill press so the the bit is centered over the Sharpie mark. Drill through the tube. If using a drill press with a DVR, then align the drill bit on the corner of each tube. Move the drill bit so that the DVR reads -22.5 mm in both the x and y direction.


Then insert Horizontal Quick Connects on both ends of parts E1 and E2 as shown below:


6. Slide pieces E1 and E2 onto the short ends of the maple block. Tighten the Quick Connectors to complete the upper portion of the workbench.

Apply the end caps.


7. Collect parts A1-A4, L-mounting brackets, T-Bolt fasteners, and mounting hardware that is included with the purchase of the maple block. On one end of each tube, install the mounting brackets using the T-Bolt fasteners as shown below. Ensure that the mounting brackets are flush with the edge of the Bosch tube.


8. Using the same tubes from step 7. Before using the tap, apply a few drop of Aluminum cutting fluid to the area where you will be threading. Use the M12 x 1.75 tap to thread the four legs on the ends opposite to the mounting brackets.

Once completed, bolt on the adjustable feet or casters. When using casters, fully secure the bolt. When using leveling feet, ensure that all 4 leveling feet are extruded to the desired height.


9. The next step is to assemble the lower frame of the workbench. The lower frame requires nothing more than additional Quick Connects to assemble. Use the remaining Quick Connect pieces to assemble the lower frame as follows:


10. The final step to the CLEAN workbench assembly is to mount the upper half of the workbench to the lower half. Set the the maple block upside-down on the work-space. Set lower frame assembly upside-down on top of the maple block so that the four legs sit on the corners of the maple block. Use the included mounting hardware and cordless drill to connect the two halves together.


Complete CLEAN Workbench with casters ready for use in the HYPER Lab!


Estimated build time for each work-bench is 4-5 hours.

For any inquiries regarding CAD models and manufacturing contact

Cryo-cycling in place – Styrofoam cups and Silly Putty to the rescue!

In this past post, we discussed using cryo-cycling  to identify and fix possible cold leaks before installing equipment in the cryostat. This prevents a lot of problems before they can happen, often saving days of cool-down and warm-up if a test has to be called off. What happens, however, when the leak opens up cold? Your experiment is happily running along at cryogenic temperatures and, all of a sudden, that last temperature cycle proves too much. A crack is allowed to widen through an epoxy joint until you have a little leak and the test has to be called off. When you warm up, the expansion of the epoxy seals the crack and the leak is gone! One option in this situation would be to disassemble the entire system, testing each possible leak location as previously discussed. If your system isn’t a simple one, this could be a serious time investment, and opens up a lot of opportunity for you to break something else, improperly re-install a component, or otherwise mess up something that was already working fine. It was for this reason we developed a system for cryo-cycling in place – using nothing more than a Styrofoam cup and some Silly Putty!

Cryo-cycling in place – Instructions based off ASTM E499/E499M – 11 Test Method A:

  • Take a Styrofoam cup and cut a hole in the bottom or side of the cup just big enough to snugly fit around the test specimen.

    Styrofoam cup photo
    A Styrofoam cup with hole cut in the bottom.
  • Wrap a thin ring of Silly Putty around the test specimen where the cup will seal against the specimen.
  • Slide the Styrofoam cup onto the test specimen, the Silly putty should extrude into the cup a little bit and form a good seal against the cup and the test specimen.

    Styrofoam cup fit around hotwire plug image.
    Styrofoam cup in place. Notice the Silly Putty sticking through at the seal.
  • Apply more Silly Putty, wrapping it around the test specimen and the inside of the cup to completely seal the bottom of the cup.

    Image of cup fitted around hotwire sensor with Silly Putty seal.
    Filling in the Silly Putty for a complete seal.
  • Fill the cup with liquid nitrogen (LN2) to start cooling down the cup and test specimen. As it cools, the Silly Putty will quickly transition through it’s glass transition temperature, first turning rubbery and then becoming a hard plastic that will be a sturdy seal.

    Image of LN2 in the Styrofoam cup
    Sealed Styrofoam cup filled with LN2
  • Sniff all fittings, welds, and solder joints with mass spectrometer by passing the sniffer probe over likely leak points. Start at the bottom of the assembly and work your way up, holding the probe on or not more than 1mm from the surface. Do not move the probe faster than 20mm/s.
  • Continue sniffing in an orderly procedure from bottom to top. Mark any leaks so they can be remedied. Be aware that helium will rise, so a leak above a previously found leak may not actually exist. It is also important to be aware of the airflow in the room, as helium can be blown around the experiment and produce small “leaks” that don’t actually exist.
  • If any leaks are identified, take corrective action and restart this procedure. You may have to let the Silly Putty warm up a while before it is soft enough to be removed.


So just how dangerous is hydrogen fuel?

When I tell people I work on hydrogen fuel, they immediately say something very wrong like, “Are you worried about a mushroom cloud over your lab?” — Mushroom clouds are from a nuclear bomb detonation, and I don’t plan on starting thermonuclear fusion anytime soon in my lab, and if I did, it might save the planet. The other statement I often get is, “Wow, don’t want another Hindenberg!” Again, very wrong. Detailed studies from NASA and others have shown that the Hindenburg disaster was likely exacerbated, and not caused by hydrogen. The Hindenburg’s sister ship, the Graf Zeppelin flew more than a million miles for nearly a decade on hydrogen before being grounded after the Hindenberg disaster. Go in and read the studies for yourself. The Hindenberg cut several corners the Graf Zeppelin did not, and you can’t expect the hydrogen to blow-out a diesel fire. The final one I sometimes get is, “Oh, the Challenger Shuttle!” again very wrong, Challenger was caused by the failure of a solid-oxide rocket booster o-ring.


So really, if I’ve just debunked the three most common misconceptions about hydrogen ‘incidents’ in a single paragraph, how dangerous is hydrogen fuel?

“Tests were devised in which tanks containing liquid hydrogen under pressure were ruptured. In many cases, the hydrogen quickly escaped without ignition. The experimenters then provided a rocket squib (a small powder charge) to ignite the escaping hydrogen. The resulting fireball quickly dissipated because of the rapid flame speed of hydrogen and its low density. Containers of hydrogen and gasoline were placed side by side and ruptured. When the hydrogen can was ruptured and ignited, the flame quickly dissipated, but when the same thing was done with gasoline, the gasoline and flame stayed near the container and did much more damage. The gasoline fire was an order of magnitude more severe than the hydrogen fire. The experimenters tried to induce hydrogen to explode, with limited success. In 61 attempts, only two explosions occurred and in both, they had to mix oxygen with the hydrogen. Their largest explosion was produced by mixing a half liter of liquid oxygen with a similar volume of liquid hydrogen. Johnson and Rich were convinced that, with proper care, liquid hydrogen could be handled quite safely and was a practical fuel — a conclusion that was amply verified by the space program in the 1960s. At the time, however, Johnson and Rich filmed their fire and explosion experiments to convince doubters.”

That was during the 1950’s “Project Suntan” days with Kelly Johnson as project lead (yes that fabled Johnson that started Skunkworks and led the design of the SR-71 Blackbird, among others). For whatever reason, perhaps to remove all doubt, the Air Force Research Labs (AFRL) decided to reproduce Kelly’s experiment in the early 1980’s at Wright Patterson Air Force Base. This experiment involved shooting each container with .50 caliber incendiary rounds and simulating lightning strikes. This time hydrogen (on the top) is being compared with kerosene (on the bottom, aviation fuel or JP-1).

This confirmed Kelly’s findings that the hydrogen fire ball dissipated quickly, providing less damage to the structure in every case versus the JP-1 test. The lightning test was inconclusive due to the container being obliterated in each case. The end result: hydrogen is safer than aviation fuel for aerospace applications involving an incendiary round penetrating the fuel tank. if you want more info on hydrogen safety in aerospace applications, NASA has loads of documentation of the history on-line, you can also check out Daniel Brewer’s book “Hydrogen Aircraft Technology.”

Don’t believe me so far? It’s hard to believe that hydrogen can be safer than conventional hydrocarbon fuels. The following video was posted to YouTube by Aaron Harris, technical director at Air Liquide. This is the single most convincing video on liquid hydrogen safety I’ve seen:

Those experiments established the safety to transport bulk liquid hydrogen (16,000 gallons +) on US highways. The results have been confirmed after nearly 50 years of practice. Even in the extreme — AirProducts had a full tanker of liquid hydrogen get rear-ended while stopped, by a glycerin truck going at 65 miles per hour. The driver of the glycerin truck was instantly killed, but the glycerin slammed forward into the liquid hydrogen tanker and caught fire, fully engulfing the liquid hydrogen tanker in glycerin flames. The strength and insulation of the liquid hydrogen tanker was so strong that I’m not even sure tanker lost vacuum — a small tube outside the tank busted and caught fire, sending a hydrogen flame up into the air that was eventually put out. As the director of liquid hydrogen safety at AirProducts is fond to say, “Nobody has ever been killed by a liquid hydrogen spill.”

But we’ve talked about blimps, planes, rockets, and liquid hydrogen tankers so far. How does this translate to conventional automotive vehicles? The National Highway Transportation and Safety Administration has a comprehensive report on the hydrogen safety studies for vehicles. The report reviews international research as well as US research. The report identifies one direct comparison between hydrogen and conventional gasoline vehicles conducted by the US Department of Energy. Here’s a few pictures from the study, try and guess which car is fueled with H2 and which car with gasoline:

Very similar to the aerospace studies, when a hydrogen storage tank ruptures and assuming a leak ignites, a hydrogen flame tends to burn out, and up and away from the structure, very quickly. One number that I remember from an introductory hydrogen technology class is that hydrogen diffuses away at 20 miles/hour, often straight up to space. Hydrogen literally is so fast that it has escape velocity and will eventually dissipate into space and the upper atmosphere. This is one of the inherent safety features of hydrogen — it doesn’t stick around long outside of a container. So as long as you don’t capture hydrogen beneath a structure where it can accumulate in dangerous quantities, you’re probably fine. Sadly, this excludes most research labs and garages where hydrogen sensors and ventilation must be carefully considered. Thankfully hydrogen is relatively easy to sense due to it’s high chemical activity.

But what about the very high pressure within the fuel tanks? Toyota has conducted numerous studies of high pressure hydrogen tank damage and has posted the videos on line to access. Two that are particularly relevant are the tank being shot at point blank by a bullet (note that the hydrogen doesn’t ignite, which is why the airforce had to use incendiary rounds). It’s a pretty uneventful video.

The next is a rear-offset impact collision — a severe loading case on the carbon-fiber fuel tank. Any other fuel tank would crumble. Remember that these carbon fiber fuel tanks are the strongest structure in the entire car. If there was a place to put a black box in the car, it would be on, or even inside the fuel tank.

The Army decided to do their own field tests to determine whether the high pressure hydrogen storage tanks were safe for the battlefield during development of the ZH2 Colorado. They started similar to the Air Force study with armor piercing ammunition. Proceeded to a Rocket Propelled Grenade (RPG) strapped to the side of a tank. And concluded by strapping C4 plastic explosive to the side of the tank.

As you can see from the figure, if your car is hit by an RPG there will be a hydrogen flame that will dissipate fairly quickly, but the tank will remain intact. This Army group strapped the RPG to the side of the tank (a perfect hit) and ignited the RPG with C4. They had C4 left over and didn’t want it to go to waste. So they strapped the rest to the side of the tank to see if they could truly get a full on tank explosion (perhaps to simulate a high-level state sponsored terror attack).

In this final case the biggest danger was shrapnel from the aluminum liner. The final sentence of the report concludes, “Storing the hydrogen at pressure will not cause any more significant safety issues than liquid fuel in the event of a ballistic penetration or explosion due to the inherently safe design of the storage systems.”

A final concern about hydrogen is that it is an emerging technology that you are probably unfamiliar with.  Do we have enough experience to use this technology safely? There are currently over 25,000 hydrogen fuel cell powered forklifts operating around the world in shipping fulfillment centers the likes of Amazon, Walmart, FedEx, and more. These systems have been in service for well over a decade and operate 24/7, having completed ~16 million refuels. Whether you knew it or not, your recent purchases were likely moved by a hydrogen fuel cell vehicle at some point during the routing to you. We just never see and interact with these vehicles. Moreover, these systems are often operated by someone that may or may not have a high school diploma — no Ph.D necessary. Still not enough? There are over 7000 hydrogen fuel cell vehicles on the road around the US. Given how much the movies like to bash hydrogen fuel (see Wonder Women, among many, many others), if there was a problem the media would have already informed us. It would be easy pickings given our embedded bias against hydrogen.

But I’ve just compared hydrogen to other fuels. What about hydrogen safety relative to lithium ion batteries like those in a Battery Electric Vehicle (BEV)? These are very different energy storage technologies, and I’m not aware of direct comparisons between the two, but we’ll try. The key difference is that a BEV cannot rapidly dissipate the energy stored in batteries like a fueled vehicle can. This means that once a cell is damaged, neighboring cells in the battery can continue to catch fire or explode at a later time. This issue has led to BEVs requiring special storage and observation after a crash. You can search for videos of first responders trying to put out a BEV that is on fire. It’s not easy and the fumes are terribly toxic. The latest article I read is not clear whether BEVs have fewer post crash fires than gasoline vehicles. This is not an admonishment of BEVs! The fact that this emerging technology is already on par or better than gasoline in terms of safety is remarkable. It would be great to see a direct study comparing BEV safety with hydrogen fueled vehicles, once both technologies have had a chance to mature.

We work with hydrogen every day in the lab. Ample opportunity for thought. I’ve often wondered why everyone has such an ingrained fear of hydrogen. I actually think the problem is convenience. Think back to your first introduction to hydrogen. Probably in a high-school or college chemistry class. Mine was in 8th grade when we electrolyzed water, filled a test-tube with a stoichiometric (ideal) mixture of hydrogen+oxygen, then lit the mixture with a match. It’s the easiest way to get a bang that gets people excited about chemistry. It’s also very impactful to see and feel the incredible energy release from such a small amount of gas. One of the most commonly watched videos of hydrogen on youtube is of a balloon filled with hydrogen and oxygen being lit on fire. But what is never added to the ends of these demos is that it’s pretty rare (and easy to engineer against) accidental mixing, within a pressure vessel, hydrogen and oxygen at the ideal ratio for an explosion. Regardless, this extreme introduction to hydrogen is embedded in our culture and memory.

So how dangerous is hydrogen fuel? In many situations where a vehicle is located outdoors hydrogen is safer than conventional liquid fuels or natural gas. This in no way implies that hydrogen is not dangerous — there are many situations where hydrogen, like any other fuel or energy storage device, can cause an accident. As one life-long hydrogen expert said to me once, “Hydrogen is no better, nor worse, than any other fuel. You just have to know the rules for working with hydrogen.” Hence our work and mission.

One final note — If you’re thinking about doing a hydrogen experiment at home, best to use caution. Hydrogen, indeed, has the highest flammability range and lowest required ignition energy of any fuel (4%-80% H2 by volume is flammable with air and a grain of sand caught in an escaping gas jet has enough kinetic energy to ignite a flow). The website has a wealth of information, including accident history to help guide you. Even the pros get caught in tough spots from time to time. Read about our near-miss hydrogen leak event sometime to get a feel for how very un-expected situations in complex systems can lead to risky repercussions. Regardless, with careful engineering, hydrogen fueled vehicles have a bright and safe future.

Let’s talk about Safety

An unambiguous yet ominous chuck key — Commons

One of the promising undergraduate students within the lab I worked in at Wisconsin was machining a part one day on a mill. He passed on the unsupervised lab-specific machine shop for risk of safety and was in the established student shop in the College — a fancy facade of a facility with a carefully organized tool closet and a windowed observation office where the head machinist, a disliked authoritarian of a person with decades of experience, could watch the shop. The student was very sharp, but left the chuck key in the mill head and turned it on. The key spun around, flew out, and took with it two of his fingers. As he’s holding his bloodied hand the head of the shop comes running out and begins yelling at him, “why did you do that!!” This would surely be a mark on his safety record. The student, in shock, ran away to the hallway outside where other students applied paper towels to his hand and helped him to the hospital.

The problem here was not a lack of authority and control, or severity of consequences, but a lack of community connection and continuous improvement in the shop practices. A chuck key with an ejector spring prevents people from leaving it in the chuck, but is more expensive. The buddy system with a mentor can help spot some of these mistakes, whatever they may be. While these improvements may seem obvious to some, common sense isn’t so common.

The WSU administration, led by the Office of Research, is undergoing an effort to re-emphasize and improve safety at our institution. I was recently informed by my chair that “at least one significant incident occurs at a university laboratory every month.” And OSHA (Occupational Safety & Health Administration) shows “that researchers are 11 times more likely to get hurt in an academic lab than in an industrial lab.” What is it about our authoritarian-legalistic structure of academic bureaucracy that naturally leads to this sub-par performance in such a critical area, and what can we do to improve?

Why Universities have a hard time with safety

I’ve written previously about how Universities evolved tree-like hierarchies. Nearly all of the reward system and feedback loops are geared towards promoting researchers to become power-driven authority leaders in their fields, which reinforces the extant authoritarian-legalistic system structure. The problem with these structures is communication. There is a very low amount of duplex communication, i.e. real conversations,,, talk. There just isn’t time for an administrator to sit down and spend quality time actually working with someone in a lab to mentor them — let alone knowing the people in their division. This results in a natural disconnection and un-grounding of administration from the people actually doing the work. I recently asked one of my friends, who is an administrator: “When was the last time you actually got a training by sitting down and doing the activity with someone, or a group of administrators?” He couldn’t remember a workshop that wasn’t primarily the traditional one way data dump.

Couple the difficulties in communication with declining resources, increasing performance pressures, and a 2-5 year graduation timer on all your primary lab personnel, and you have a recipe for a safety nightmare.

This means that it’s all too common to hear safety bulletins from administrators along the lines of the following: “make a new resolution to make this year accident free,” or to add “safety to annual performance evaluations,” or to “please report even the minor accidents,” and emphasis that “failure to report an incident… does result in consequences.” This is the easiest thing for an administrator in a power structure to do. Aside from invasive intrusions into labs, what else can they do? But this leads to other problems.

I once knew an administrator who still conducted research in their lab. One day, a post-doc accidentally mixed two substances in the fume hood, leading to an explosion that destroyed the hood. The administrator, under pressure to reduce accidents in their unit, did not report the incident to others as they were the only required chain of reporting. Months later, a young faculty member in their unit had a similar incident that destroyed another fume hood. A year later, a similar accident sent 16 people to the hospital at a neighboring institution.

When framed like this, the lack of communication almost seems criminal. Clearly, the sad reality is that these authoritative declarations coupled with punishments, within our communication-deficient authoritarian-legalistic system structure, can lead to corruption and actually be detrimental to the broader cause they intend to help. This command and control approach boils down to what is known as the deterrence hypothesis: the introduction of a penalty that leaves everything else unchanged will reduce the occurrence of the behavior subject to the penalty. I’ve previously written about the problems of applying the deterrence hypothesis to grading of coursework. In this case, safety is connected to my performance evaluation — which is primarily used for raise allocations and promotion. So in short, if an accident happens, my status and pay within the institution will suffer. So does this feedback mechanism promote better safety or lack of reporting — the most direct effect is lack of reporting. This is also presumes that the permanent disabling damage from losing fingers or another accident is not deterrence enough — the approach assumes that faculty delegate all risks to students rather than doing the activity themselves.

In a famous study titled, “A fee is a price” researchers investigated the efficacy of the deterrence hypothesis at mitigating the undesirable behavior of picking a child up late from daycare. This is low — abusing the personal time of a lower-paid caretaker charged with the health and well being of your child. In many ways this parallels the minor accidents, cuts, and knuckle bangs we’re being asked to report. In order to couple these to performance evaluations, a non-arbitrary metric must be created to decide how big the penalty, or price, should be. Contrary to expectations, the researchers performing the study found that adding the penalty actually increased the negative behavior that it intended to deter. The researchers deduced that the penalty became a price — if I’m late, I’ll pay the $20 and everything is ok — regardless of whether the caretaker had other plans. Perhaps the most troubling finding from the study was once the penalty was systemized, the bad behavior continued regardless of whether the penalty was removed or not. Once you marginalize or put a fee on a person, it’s tough to treat them as a person with rights and dignity again.

I’ve seen this play out many times with daycares, teams, and communities I’ve been involved. Reliably the diminishing of people and disruption of personal connection leads to the demise and under performance of the organization. When an authoritarian is presented with this evidence contrary to their belief, they reliably counter with, “oh I’ll make the penalty severe enough to deter the behavior.” What else can they do? This approach, in the absence of appropriate developmental scaffolding, leads to a depressed environment adverse to uncertainty. Everyone becomes afraid to report safety, afraid to discuss safety, afraid to try new things and push the limits (isn’t trying new things and pushing the limits called research?) — often simply because trying new things is no longer the norm. When something is not the norm, it becomes an uncertainty risk and threat.

I once was having a discussion with an administrator about a new makerspace on campus. This prompted the statement, “But we’ll never be able to control the safety!” To this I immediately responded: 3D printers are robotic hot glue guns with safety shrouds! Every campus in the US has a gym with a squat rack (people put hundreds of pounds on their back on a daily basis with poor form), climbing wall (someone could fall!), pool (but what if someone drowned!), and a hammer/discuss/shotput/javelin toss (yikes!).

Arbitrary targeting of risk/blame is another characteristic of authoritarian/legalistic organizations because they lack established heuristics, a.k.a. processes, to work through safety scaffolding of new activities. Shot put and the hammer toss are established activities that our culture has normed to, where the risk in developing the established safety protocol was encumbered centuries ago. Less of a need for an administrator to CYA. Moreover, a command and control approach isn’t what makes them safe — it’s connections and discussions with people. The disincentive for not using the squat rack correctly is chronic back pain, something I deal with on a daily basis. That risk didn’t stop me from squatting incorrectly! The problem was ineffective coaching/scaffolding. Telling the coaches to coach better won’t explicitly fix that. And we can’t always rely on starting a new facility fresh with appropriate safety from the beginning.

I once attended a safety seminar, led by a well respected researcher at another academic institution. The researcher described the brand new building they were having built, and all of the safety protocols they implemented to make it safe. Afterwords I asked the researcher their approach for improving safety within established student clubs. The response stunned me: “I’m not really sure. We have another building for that. We never allow students to work after hours unsupervised.”

They had nearly entirely avoided teaching intrinsic safety culture! The students were never allowed autonomy to make decisions! I told myself I’ll never bring in a student from that institution. This exemplifies what happens when we are granted huge resources without having to perform or evolve to a level that justifies them like in industry. It was almost Orwellian. Certainly not the future our society and university needs.

After having a string of safety incidents in their unit, an administrator and safety board required every club and lab to have a “designated safety officer” or a designated authority to control safety for the group. After a few months in this position, one lab’s “safety officer” lamented to me, “Sometimes I need to be the bad guy because people don’t take safety seriously. But it gets tiring. They dislike me for it, blame me when stuff goes wrong, and they still don’t take safety upon themselves.”

This is directly analogous to the problem of quality control faced in Lean Manufacturing. In Lean, the question comes up of whether something you’ve manufactured meets the design specification. Do you hire a quality control czar to stop production if product starts coming out not to spec or unsafe? Ever heard a story of someone who was frustrated with the quality cop coming over to tell them things were wrong yet providing no explanation what was wrong or how to fix it? Moreover, the only way to ensure 100% quality/safety is 100% inspection — not a sustainable or scale-able approach. The Lean approach is to design quality/safety control into the production process — if the part can’t be made wrong/unsafe, it’s much easier to achieve 100% safety/quality. Moreover, if everyone is responsible for checking safety/quality during the production process, you just made everyone in your group a safety officer and multiplied the odds of spotting a risk before it’s realized.

Another common characteristic of authoritarian-legalistic approaches to safety is the posting of negative signage/reminders. “No ___ allowed.” “Don’t do this!” etc. Here’s a great counter example from Seth Godin titled, “How to make a sign.” The problem is we become numb to these negative associations and quit paying attention. That’s why we have “Did you know?” documents in our lab that just describe the right process for doing something. We try to include a funny meme at the top to get people to positively associate and look at these. Here’s an example posted near a compressed gas bottle area:

It boggles my mind why lab leads do not have safety procedures posted by all key lab processes and equipment. It’s really simple — if something goes wrong you change the procedure. Changing the procedure is orders of magnitude cheaper and easier than changing the equipment or personnel. It’s therefore much easier to continuously improve procedure.

So we’ve shown through multiple ways the safety shortcomings of traditional authoritarian-legalistic bureaucratic structures. How do we get beyond these to cultivate a sustaining community and culture of safety within such institutions?

Let’s talk about Scaffolding Layers of Safety

In short, the real solution to safety is performance based funds from a diverse array of sources, like in industry. This naturally dovetails with a diverse, sustaining and supporting lab community. If you’re operating efficiently and effectively, you can’t stand the loss of a well trained person, even for a few days. But that’s a chicken or the egg conundrum for us in universities. I’ve written previously about the challenges and tips for building sustaining lab communities. It’s not easy! In short, you have to scaffold multiple orthogonal value sets. But the end result can literally be a life-saver!

About 6 months ago we had a near-miss hydrogen venting event in the lab caused by a power failure and a pressure relief valve freezing shut. Because we had multiple layers of safety engineered into the experiment, and multiple layers that we could communicate within the lab, and university, a potential tragedy was avoided. In the end, instead of being reprimanded, we got a 5 month extension on the project, upgrades to the lab, and were told by administrators, “This was not an accident because you are working hard to do everything right.”

In a recent post I provided a scaffold to grow agency in engineering education. The key premise being that values change, and we need a scaffold that relates to many different value sets. Safety is no different. This provides the “layered” approach to safety that is popular in software security and other forward thinking fields. Here are several levels and examples of what we do in the HYPER lab to help activate the appropriate values:

Authority: Typical to most research labs. A grad student, or preferably a team of 2 grad students and 2 undergrads are responsible for maintaining an experimental or fabrication facility. Their names and pictures are associated with the project both in person and virtually through the lab website. They also are given an instant communication channel that the lab can see specific to the experiment/facility. Notice I was careful to connect authority to responsibility and have carefully steered clear of the power-command authority traditional of academia.

Legalistic: Each experiment has a Safety Protocols and Procedures manual that is continually refined (send me a note if you want to see ours, I don’t want to display online in case of nefarious actions.) The safety manual includes a Failure Modes and Effects Analysis (FMEA) that predicts all of the likely safety issues and emergency protocols. We implement the buddy system for changes to experiments and manuals — you need to have someone else there to approve. We also are continuing to develop a common lab-rules, standards, and values banner that goes above the doors to spaces. We are working to develop standard trainings for the right and wrong ways to utilize plumbing fittings and seals common in our work. We emphasize use of engineering standards wherever applicable.

Performance: Once a student is proficient with the responsibilities, literature, trainings, and practices in an area, they develop a did-you-know? heuristic process document. This informs people of the necessary steps unique to the space for accomplishing a task. Students at this level are expected to begin bringing in their own resources and recruit their own students to working on their project. We are also implementing a traveling safety award for the lab and tracking days without incidents.

Community: All of the lab members (without me) go to lunch together once a week. In addition we work together as a lab for a 3 hour time-block once a week on lab community builds and needs, including safety. This is greatly enabled by allowing all of the students to contribute to our community website (this site) and our Slack message board. We offer tours of our lab as frequently as possible to gain critical feedback and advise from potential stakeholders or partner labs. I’ve written previously about Tradings Places and Ways.

Systemic: We’ve established the expectation of all lab members to contribute and cultivate our system and community by looking for and enhancing restoring feedback loops that improve our efficiency in each of these levels. We do this by building our people from the ground up — we seldom import talent into our culture. This is very similar to Toyota and other lean production environments. No surprise, our lab has the Lean Philosophy of 5-S posted throughout: Sort, Sweep, Systemize, Standardize, Sustain.

So far things seem to be working. We have equipment and builds that I’m sure my colleagues think are ludicrously difficult and safety risks. We’re the only lab in the country that focuses on cryogenic hydrogen — which has the highest thermal, fluid and chemical power gradients. Hydrogen should not be taken lightly! But I also know that the students are developing in incredible ways and coming together as a community to make it happen, safely. One of the reasons I know this is the fact that they’re not afraid to talk about safety, and they are having fun with it!


So let’s talk about safety! Send me your comments and suggestions: jacob.leachman<at>

Cold Rolling Indium Foil

Indium foil is used here in the HYPER lab to create gaskets for seals within cryogenic hydrogen systems. Research with cryogenic fluid systems requires uniquely shaped seals that do not degrade at the extreme cold temperatures, and Indium is recommended by several leading experts. The required gasket profiles are cut out of large thin sheets of Indium, this process produces scrap material that is not sufficiently large to use again. Due to a relatively low melting point we’re able to melt the scrap Indium to form an ingot that can then be re-rolled into a new sheet to be used. The preferred thickness of this sheet is 0.05-0.025 inch (1.27-.635mm) and the tooling in the WSU heat treatment lab has the ability to produce this thickness. Here’s a guide to the HYPER lab’s process for producing new sheets of foil from an ingot of Indium.



  • Indium scrap ingot
  • Wax paper
  • Digital caliper
  • Hydraulic cold rolling mill
  • Retractable blade knife
  • small container for indium scrap



  1. Using the retractable blade knife cut off any surface impurities from the indium ingot while collecting any material cut off for re-melting. Here’s a guide to safe use of a retractable blade knife.

    Ingot after removing surface impurities.
    Ingot after removing surface impurities.
  2. Slice the ingot into two, similarly, ~1 cm thick, ~3 cm in od, sized pucks so that the material will fit in the cold rolling mill. ingot-mid-cutingot-cut-in-half
  3. The rolling mill is in Dana 236. You need to get approval from either Dr. Field or Dr. Wo before using the mill. Turn on the cold rolling mill and position the pedal so that it is accessible from both sides of the machine.

    Available hydraulic cold rolling mill.
    Available hydraulic cold rolling mill.
  4. Cut a piece of wax paper that is large enough to fit through the mill while folded around the metal sample.

    Indium puck after one pass.
    Indium puck after one pass.
  5. Fold the wax paper in half and place the metal sample inside to prevent sticking to the rolling cylinders.
  6. Begin by setting the mill to the width of the first puck to be rolled.
  7. Start making passes through the mill reducing the thickness by .4mm (1/4 turn of the adjustment handle) per pass until the puck is roughly 5mm thick.

    Rolling mill adjustment handle.
    Rolling mill adjustment handle.
  8. After every 3-4 passes the thickness of the Indium measured with the caliper.
  9. After reaching 5mm thick the metal will have to be rotated 90 degrees to prevent curling and each pass was lowered to a .2mm size reduction, slowing the rolling process will reduce waves in the sample. 1925-inch-measurment

    Indium sheet before first rotated pass.
    Indium sheet before first rotated pass.
  10. At roughly 2.5mm sticking between the metal sample and roller will begin to become an issue that must be watched for and thickness measurements were taken after each pass.
  11. Continue making passes through the rolling mill until the Indium sheet reaches the required 1mm in thickness.

    Finished Indium sheet
    Finished Indium sheet
  12. Safe the rolling mill by backing off the adjustment handle, turning the machine off, and locking the room when you leave.
  13. Once the material has been rolled, store it in a ziplock baggy in the drawer labeled “Indium” in ETRL 221.

Now you too can make effective thermal interfaces for use at cryogenic temperatures. Thanks for reading!


Extruding Indium Wire

We use indium wire for creating cryogenic seals in the HYPER lab. We buy most of our wire from Indium Wire Extrusion (IWE). Indium is expensive however, quoted by IWE at $180/oz. Rather than selling the wire back for half its original price, we like to recycle our indium by melting it down and re-extruding it into usable indium wire. Indium’s low melting point of 156.6 °C (313.9 °F) and softness (Mohs hardness 1.2) make this process cheap and easy. We have the capability of extruding 0.0625 inch (1.5875 mm) and 0.1 inch (2.54 mm) diameter indium wire with the equipment we have in the lab.

A 13.6 oz. block of indium worth $2,450.

The following article provides an easy-to-follow guide to the HYPER lab’s indium extrusion process. The hope is that this guide will serve as training for those working in the HYPER lab, as well as a good starting point for others who would wish to extrude indium for cryogenic applications.


The HYPER lab extruder setup.



  • Hydraulic extruder
  • Hot plate capable of at least 200 °C (the higher the better)
  • Flat copper plate
  • Puck cast mold sized for extrusion chamber
  • Indium scrap
  • Empty spool
  • Metal bin with 2-3 inches water for quenching
  • 3/8″ Hex key
  • Hammer
  • Metal shaft with diameter smaller than puck diameter
  • Slip-joint adjustable pliers
  • Retractable blade knife
  • Large pipe wrench
  • 2 wood or metal blocks of the same size



  1. Gather indium scrap. Make sure scrap pieces are small enough to fit into puck mold.

    Indium scraps in a cup and in the puck mold. Notice the puck mold is placed on top of a copper plate.
    Indium scraps in a cup and in the puck mold. Notice the puck mold is placed on top of a copper plate.
  2. Place copper plate onto hot plate. Place puck mold onto copper plate.
  3. Heat the hot plate to around 250 °C (or higher for faster melt).
  4. Put indium scrap into mold and wait for indium to melt. For faster melting, push indium down into the mold.
  5. While waiting for indium to melt, extruder can be assembled. The assembly consists of three parts: die, die holder, and extrusion chamber. Begin by placing the die into the die holder.

    From left to right: Extrusion chamber, die, die holder.
  6. Screw the extrusion chamber into the die holder.
  7. Bolt the assembly onto the end block of the hydraulic extruder.

    The completed assembly attached to the end block.
  8. Once indium has begun to melt, it will fill the mold cavity. At this point, add more indium scrap until the mold is full.

    Melted indium.
  9. Using the adjustable pliers, grab the hot copper plate (with mold on top) and dip plate, mold, and indium into the water to quickly cool the assembly. You may now turn off the hot plate.

    Quenching of indium slug.
  10. Once water has stopped boiling and making sure all parts of the assembly have been cooled, take the assembly back out of the water.
  11. Placing the mold with indium stuck inside it onto two wood or metal blocks, use a hammer and shaft to knock the indium out of the mold.

    Here’s one way to get the indium out…
  12. Cut off impurities using the retractable blade knife.
    20160706_161741_HDR20160706_161901_HDR (2)
  13. Place indium puck into extruding chamber of extruder. Place the metal spacer behind it.

    Indium puck inserted in the extrusion chamber (without metal spacer).
  14. Turn on the hydraulic extruder by opening the compressed air valve and set it to ‘EXTEND.’ Then get ready on the output end of the extruder with the empty spool. It is best to have two people for this task: one controlling the extruder, one spooling.
    20160708_103330_HDR (2)
  15. Utilize the pressure regulator to modulate the speed of the extruder piston. This can be increased during free float piston motion and modulated during extrusion to achieve desired spooling speed.
  16. Wait until the plunger reaches the indium and indium wire begins to emanate from the output end of the extruder. Be prepared, since wire will come out at high speed depending on the pressure regulator settings.
    20160706_162201_HDR (2)20160706_162326_HDR (2)20160706_162357_HDR (2)
  17. As wire emanates from the output end, wrap it around the spool while keeping a small amount of tension on the extruding indium.
  18. When you hear the hydraulics begin working harder than they were initially, set the extruder to ‘RETRACT.’ When you hear this sound, the plunger is trying to extrude the metal spacer.
  19. Break the end of the indium wire away from the extrusion outlet. You should now have a spool of indium wire.

    The final product.
  20. Disassemble the extrusion assembly in order to remove the metal plunger. At this point a large pipe wrench will likely be necessary to unscrew the extrusion chamber from the end block. The remaining indium can be left in the extrusion die until the next extrusion.
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