How to Pressure Cast Alumilite Clear Slow Epoxy Resin

How to Pressure Cast Alumilite Clear Slow Epoxy Resin


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Resin pressure casting is the process of using a pressure chamber paired with an air compressor to help remove bubbles from resin. If you are creating goods that cannot have a single bubble, pressure casting is the most reliable method with the quickest cure time.  

We use and recommend pressure casting with Alumilite Clear Slow urethane resin if you need to move fast. Most other naturally setting resins require a minimum of 48-72 hours to cure fully. These types of resins are typically used when casting larger goods such as resin river tables that cannot physically be placed into the average pressure chamber.



 1) Alumilite Clear Slow Urethane Resin


2LB and 16LB Kits can be purchased from Alumilite 

2) Silicone or HDPE Mold

It's best to custom make this for your requirements but you can grab a basic one like this from Amazon:

 TIP - Heat your mold (using a convection oven) before pouring the resin. Resin heats up as it cures and if the mold you pour your resin into is at a different temperature than the resin, there is a chance for moisture. This moisture can impact the color and curing of the material.

3) Pressure Pot - Retrofitted Paint Pot


Check out these two resources on how to retrofit the paint pot:

Pressure Pot Converted to a Resin Tank: 

Pressure Pot for Casting Resin:

4) Air Compressor


5) Timer - A Maker watch is best :)

You'll need a timer to track the Alumilite Clear Slow open time of 12 minutes. This is the amount of time you have to mix before the resin starts to cure.

6) Scale

Alumilite Part A & B are 1:1 mixed by weight.


7) Mixing container & Mixing Sticks


Popsicle sticks works for us, but you can use anything that works for you.  

9) Optional - Pigment or Dye


 We use black diamond pigments and Alumilite Dye.


1) Measure the amount of resin needed

This varies by what you are pouring and is a simple volume calculation. Our good friend Jeff Mack Designs summarizes it up well in this blog post. Alumilite also provides a good volume calculator 

2) Pour Side A, followed by side B

Both Casey Martin of Wine Country Woodworks and Zac Higgins of NV Woodwerks share a wealth of resin casting knowledge on their respective channels. These two guys are literally how we've learned it all.

3) Mix thoroughly

Ensure you scrape the sides and bottom of the mixing container to make sure there is no unmixed material left. The resin will get warm in the process and as it gets closer to the open time of 12 minutes.

You don't want to see any differences in liquid - it should look like one uniform body without any wisps.

4) Add optional pigment

Please wear a mask when working with pigment. 

5) Take the heated mold and pour in the resin

Careful the mold can be hot!

6) Start the air compressor to get it charged up.

You'll be cutting into your open time if you don't have this ready to go.

7) Pour resin into the mold and place it into the pressure pot.

The pot should be in a temperature-controlled room in a safe area where it will not be disturbed

8) Securely tighten the lid of the pressure pot.

Apply even torque to the latches.

9) Pressurize the tank using the air compressor and ensure you are not exceeding the max tank PSI before the 12-minute mark. 

This paint pot we recommend has a max 50 psi capacity. Pots of this nature typically vary between 50- 80psi. 

10) Let the tank sit pressurized overnight

Let the pressure work to pop the bubbles. The amount of the time in the pot varies by what you are casting. Typical de-mold time varies between 2- 4 hours but the smaller time in which you are casting generally requires more time under pressure. We would recommend experimenting on the de-mold time over a few runs to see what gives your application the best results.