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HOW TO PRESSURE-CAST RESIN
6 min read
Pressure casting is the most practical, albeit noisy, way of casting resin parts in silicone molds. For my purposes-- Myth-Babies ball-jointed dolls and other products related to Tamara Henson Studios, LLC-- it is awesome and also cost-effective in the long run.
Here's what I did to set up a pressure casting system:
Buy THIS: www.harborfreight.com/2-1-2-ha…
It's not huge, but it's a good starter for around $100. I modified the tank by 1) removing the paint uptake steel tube (it unscrews with some pliers), 2) installed a plug and a cap to shut off the hole from the uptake tube and another opening off the gauge that isn't necessary for the casting process. I thread-taped all the screw-in bits and tightened everything down with an adjustable wrench.
I bought a small "donut" style air compressor from Wal-Mart and an air hose and connector kit (with thread tape in the pack!), all for under $80. Also, ear plugs... I hate loud noises! And safety goggles if you don't want to live on the edge like me.
I hooked up the air hose with a solid coupling (not an air-leaky quick-coupling) and left it attached, since this setup has one function. Between the air tank and the compressor, I have two safety valves to release air, so it's not that scary to leave it, and it's completely depressurized when not in use anyway. I tested the system by turning on the compressor and screaming every time the faulty safety valve released too early.
After upgrading to a functional safety valve, it works pretty well. The goal is to get the pressure pot to 60 psi and stay there with minimal or no leakage. My pressure pot stays between 57 and 60 psi for a couple hours (which is fine for casting most resins) and doesn't go below about 40 psi when I ignore it overnight (on those long 24 hour silicone vigils). I have witnessed no ill effects from having the silicone dip down to the lower psi. I just bring it back up to pressure when I wake up.
THINGS TO KNOW:
*My safety valve was faulty and required replacement.
*My pressure pot's gauge stopped working after a month or so. The compressor's gauge still works accurately, though, so I haven't replaced the pot's gauge.
*Tweaking of everything is to be expected, although I hope this guide helps a bit. Let me know what works better for you!
*Pressure casting is dangerous, even with proper precautions. Read all instructions for every device you buy!
*Be smart about safety: Goggles, ear plugs, and no jarring or moving either device while they're in use.
*Other stuff... but it's too late to think right now... Ask me!
RULES AND NOTES FOR SILICONE AND RESIN:
1) If you plan on pressure-casting resin, you should also plan on pressure-casting your silicone molds, too! Silicone molds that are NOT pressure cast have larger bubbles that will probably compress in the pressure pot. This means parts of the mold may collapse inward and lead to undesirable shapes in the resin.
2) Pressure cast your silicone at the same PSI you will be using for your resin for consistency's sake. The same thing mentioned in number 1 above can happen, but on a less dramatic scale.
3) Silicone ages like crap once it's used to make molds. Depending on the brand you use, there can be shrinkage and brittleness (?) in the finished molds. The shelf life varies depending on time and use.
4) Resin ages like crap once you buy it. Don't spend a crap-ton of money on resin until you're ready to use it, and expect to use it quickly. Same for un-cast silicone, for that matter...
HOW TO USE A PRESSURE CASTING SYSTEM:
1) Prep all molds in advance. Figure out which ones will fit and in what order. Seal all corners and edges. (I use LEGOs with "grass" plates I've cut into different sizes for different uses. All I have to seal is the bottom corners). Silicone is expensive. It is more expensive flowing across your floor!
2) Mix and pour silicone according to product instructions. Gloves!
3) Stack the molds in the pressure pot with a lot of clearance at the top. The displacer needs room to blow air in!
4) Set lid on pressure pot. Tighten opposite wingnuts to hand-tightness (no tools!).
5) Turn on air compressor to 60 psi according to gauges. Turn off air compressor when it reaches the proper PSI.
6) Check PSI levels during casting time, periodically, and use compressor as needed. (This is another reason why quick-coupling isn't necessary. Refills!)
7) Depressurize pressure pot by pulling ring on safety valve until gauge reads zero.
8) Loosen opposite wingnuts at the same time until all are loosened.
9) Remove lid and remove molds from pressure pot.
10) Prep molds to fill part two and repeat the process, keeping in mind the room in your pressure pot.
TO CAST RESIN:
1) Clean and prep molds: spacer straws, rubber bands, fill slots and the like.
2) Mix resin and fill molds. This is usually a much quicker process because resin cures faster than silicone!
3) Stack molds in pressure pot and follow steps 4-9 above.
4) Don't try to fill more molds than the pot-life of your resin allows. Get the molds filled and in the pressure pot ASAP! Otherwise, you'll waste expensive resin!
This general guide is not intended to be all-inclusive, so I glance over details of silicone and resin mixing and pouring and moldmaking, etc. Feel free to ask any related questions, though!
Thanks for reading, and I hope it's been helpful!
Tamara
Here's what I did to set up a pressure casting system:
Buy THIS: www.harborfreight.com/2-1-2-ha…
It's not huge, but it's a good starter for around $100. I modified the tank by 1) removing the paint uptake steel tube (it unscrews with some pliers), 2) installed a plug and a cap to shut off the hole from the uptake tube and another opening off the gauge that isn't necessary for the casting process. I thread-taped all the screw-in bits and tightened everything down with an adjustable wrench.
I bought a small "donut" style air compressor from Wal-Mart and an air hose and connector kit (with thread tape in the pack!), all for under $80. Also, ear plugs... I hate loud noises! And safety goggles if you don't want to live on the edge like me.
I hooked up the air hose with a solid coupling (not an air-leaky quick-coupling) and left it attached, since this setup has one function. Between the air tank and the compressor, I have two safety valves to release air, so it's not that scary to leave it, and it's completely depressurized when not in use anyway. I tested the system by turning on the compressor and screaming every time the faulty safety valve released too early.
After upgrading to a functional safety valve, it works pretty well. The goal is to get the pressure pot to 60 psi and stay there with minimal or no leakage. My pressure pot stays between 57 and 60 psi for a couple hours (which is fine for casting most resins) and doesn't go below about 40 psi when I ignore it overnight (on those long 24 hour silicone vigils). I have witnessed no ill effects from having the silicone dip down to the lower psi. I just bring it back up to pressure when I wake up.THINGS TO KNOW:
*My safety valve was faulty and required replacement.
*My pressure pot's gauge stopped working after a month or so. The compressor's gauge still works accurately, though, so I haven't replaced the pot's gauge.
*Tweaking of everything is to be expected, although I hope this guide helps a bit. Let me know what works better for you!
*Pressure casting is dangerous, even with proper precautions. Read all instructions for every device you buy!
*Be smart about safety: Goggles, ear plugs, and no jarring or moving either device while they're in use.
*Other stuff... but it's too late to think right now... Ask me!
RULES AND NOTES FOR SILICONE AND RESIN:
1) If you plan on pressure-casting resin, you should also plan on pressure-casting your silicone molds, too! Silicone molds that are NOT pressure cast have larger bubbles that will probably compress in the pressure pot. This means parts of the mold may collapse inward and lead to undesirable shapes in the resin.
2) Pressure cast your silicone at the same PSI you will be using for your resin for consistency's sake. The same thing mentioned in number 1 above can happen, but on a less dramatic scale.
3) Silicone ages like crap once it's used to make molds. Depending on the brand you use, there can be shrinkage and brittleness (?) in the finished molds. The shelf life varies depending on time and use.
4) Resin ages like crap once you buy it. Don't spend a crap-ton of money on resin until you're ready to use it, and expect to use it quickly. Same for un-cast silicone, for that matter...
HOW TO USE A PRESSURE CASTING SYSTEM:
1) Prep all molds in advance. Figure out which ones will fit and in what order. Seal all corners and edges. (I use LEGOs with "grass" plates I've cut into different sizes for different uses. All I have to seal is the bottom corners). Silicone is expensive. It is more expensive flowing across your floor!
2) Mix and pour silicone according to product instructions. Gloves!
3) Stack the molds in the pressure pot with a lot of clearance at the top. The displacer needs room to blow air in!
4) Set lid on pressure pot. Tighten opposite wingnuts to hand-tightness (no tools!).
5) Turn on air compressor to 60 psi according to gauges. Turn off air compressor when it reaches the proper PSI.
6) Check PSI levels during casting time, periodically, and use compressor as needed. (This is another reason why quick-coupling isn't necessary. Refills!)
7) Depressurize pressure pot by pulling ring on safety valve until gauge reads zero.
8) Loosen opposite wingnuts at the same time until all are loosened.
9) Remove lid and remove molds from pressure pot.
10) Prep molds to fill part two and repeat the process, keeping in mind the room in your pressure pot.
TO CAST RESIN:
1) Clean and prep molds: spacer straws, rubber bands, fill slots and the like.
2) Mix resin and fill molds. This is usually a much quicker process because resin cures faster than silicone!
3) Stack molds in pressure pot and follow steps 4-9 above.
4) Don't try to fill more molds than the pot-life of your resin allows. Get the molds filled and in the pressure pot ASAP! Otherwise, you'll waste expensive resin!
This general guide is not intended to be all-inclusive, so I glance over details of silicone and resin mixing and pouring and moldmaking, etc. Feel free to ask any related questions, though!
Thanks for reading, and I hope it's been helpful!
Tamara
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Solana is here!
1 min read
SOLANA: A Pathos Sidetrack is now on Amazon Kindle for just $0.99! It's a novella about a PATHOS character who is near and dear to my heart. She just demanded her own little book! I also designed the deco-style cover. Plus, the paperback is forthcoming!
Please, oh please go check out my books and let me know what you think! Also, share with your sci-fi/fantasy lovin' friends!
Starting, if you want, with Solana: www.amazon.com/dp/B00HU20UW4
Love and hugs,
Tamara
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CONTEST FOR NOVEL PRIZE
1 min read
I am currently holding a contest for my Pathos series of novels over on Facebook. Prize packages include digital copies of Volume 1 and the new Pathos Sidetrack, an autographed Rowan Jun paperback, and discounts galore! Go check it out:
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Winds of Change, yet again
2 min read
TATTOO/PIERCING NEWS: After expressing my interest in starting my own studio sometime this year, I was fired by my cousin from his studio. Whether his motivation was really business-related or personal, I can't determine. Or at least, I'm taking the high road and not airing dirty laundry here. I am still hopeful to find funding to start my own, but will again be jobless for a bit.
NOVEL NEWS: I'll be releasing a Pathos Sidetrack novel before I release Volume 2, Silver Empress. The Pathos Sidetrack novels will be backstories and/or short story collections that complement the main Pathos series storyline. Some will directly tie into the main story. Some will feature characters that didn't get enough love in the original storyline. So it's all still the Pathos series! And until I find steady employment, or open my studio, I should have plenty of time to write!
MYTH-BABIES: I'm hoping that whatever space I lease for my tattoo/piercing studio will have additional rooms for moldmaking and casting. That way, when it's slow at work, I can work on my books AND dolls. But I'm really stuck for a bit now. I sculpt on the dolls to take my mind off the stress of being broke.
Love and cuddles,
Tamara
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