Is a pressure pot necessary for casting?

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DaveTas

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Hi folks, I see "clear" casting resin advertised on the net. Does this mean they cast clear without a pressure pot?
Is a pressure pot absolutely necessary to make acrylic or resin blanks?

I'd love to try casting but would also love to avoid another piece of expensive gear If I could..

thanks in advance for help.
 
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It is not absolutely necessary; but for the faster curing resins (Alumilite, Alumilite Clear Slow, etc...basically resins that cure in minutes) the odds are that, without a pressure pot, visible bubbles will be trapped in the resin as it cures.

With polyester resins, I have cast without a pressure pot. These, in my experience, have cure times of hours. If encapsulating something with a complex shape, there is chance that air can be trapped on the low side of the piece. It will leave a bubble. If the air pocket is large enough, there will be a visible bubble, even if the resin is pressurized during the cure. The poured mold can be manipulated to help clear trapped air.

Pressure does not remove bubbles, it only shrinks them.

Hope this helps some.
 
I'm not totally sure of your meaning of "Clear", but it seems to indicate that you may be taking that word to be "without outside influences". The word "Clear" means "to be very glass like, not tinted, not yellowish," "transparent/crystal clear". Therefore "Clear castings" in and of itself is not connected to pressure pots, although most are done that way.

Casting without a pressure pot is not "absolutely" necessary, but if a pressure pot is not used, it requires a lot of experience, natural talent and understanding of different resins and the chemical processes.
 
Epoxy resins such as Liquid Diamonds does not need a pressure pot because it is very thin and stays that way for a long time so the air bubbles have a better chance of escaping. Any other resins do need pressure to be successful. You risk the chance when you do not. A pressure pot is not all that expensive and many real good ones can be found on Craigs list or even ebay. The cost is in the resins. They are not cheap. No one said this was not going to be an inexpensive hobby. :)
 
I was told, gentle pouring of slow curing resin with a little heat (heat gun, lamp, plate warmer) will eliminate bubbles. Have also heard the Deep pour resin helps but have not tried it yet.
 
The new deep pour is epoxy resin, which is why you can get away without using a pot. However, epoxy resin can take more than 3 days to properly cure. A lot of thin pours can be hit easily with a heat gun to pop bubbles but I don't know how well it will work with deep pours. Your best bet is to slightly warm your resin to thin it prior to mixing. Alumilite clear and slow will always leave bubbles in the cast if you pour without a pot. They may be small but you will see them when you sand as they will with sanding dust. Poly resin can be poured without a tank but like others said above, it's a small investment to get one for the risk of failures in resin casts. Resin is t cheap and never lasts long enough when they all turn out.
 
jttheclockman said:
Epoxy resins such as Liquid Diamonds does not need a pressure pot because it is very thin and stays that way for a long time so the air bubbles have a better chance of escaping. Any other resins do need pressure to be successful. You risk the chance when you do not. A pressure pot is not all that expensive and many real good ones can be found on Craigs list or even ebay. The cost is in the resins. They are not cheap. No one said this was not going to be an inexpensive hobby. :)
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I'm sure I told my wife what a cheap hobby this was 🤔🤔!

She likes the results and maybe, just maybe I might have forgotten to mention the costs incurred.😉

Re pressure pots though , OK it's not a cheap item but replacing part of the house or workshop or losing a limb if the pot fails is kind more painful ( than the earache from buying the pot ). Just stress it's necessary safety equipment to purchase. I mean she wouldn't want you injured ( would she ??🤷‍♂️)
 
Alumilite clear and clear slow are urethane resins. A byproduct of their chemistry is CO2 production. A pressure pot is needed to keep the CO2 in solution and to not form bubbles.

I know several who cast polyresin without pressure. I do not.
Do a good turn daily!
Don
 
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