How much pressure?

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JPW062

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I was told I need minimum 80psi pressure to cast alumilite successfully while most resins only require 50 or 60.
True?

What pots can handle this pressure?
I'm not looking for the cheapest pot out there. I also don't need the most expensive.
 
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tom wood

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I use 45 to 50 lbs on most stuff. I go up to 70 lbs If I'm casting something with alot of voids , Cholla cactus skeleton for example. Never had a problem. Always keep in mind the maximum working pressure of your pot and stay below it....
 

budnder

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I'm at 30 to 40 lbs and never had an issue... using a converted Harbor Freight paint pot. I had to make a new gasket for it (out of Smooth-On) to get it to hold pressure for any length of time.
 
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mark james

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Yup! I was good at 40 PSI. My HF Pot with added safeties held for 24 hrs. I casted Alumilite for 60 minutes at 40 PSI; very few failures (Recently loaned my PP to another IAP member).
 

JPW062

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I have experience with harbor freight products. I'm not interested in buying something I have to rework to get functional. I would rather build from scratch than remake someone else's junk.

What off the shelf can do 60+ PSI?
 
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Pressure pots are made for painting, so most will need some reconfiguring. Lately I've seen a few that are made for casting. One looks like a reworked HF pot for $200 from Artmolds.com - you can do it yourself for about $120-$125 including the pot, the other is a C A Technologies for around $350. There are probably others.
 

robutacion

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Pot pressures are an interesting subject but in general terms about 30 to 50 PSI is sufficient for regular casts that don't have cracks or small crevices where the resin needs to reach, for that, you will require a little pressure and in this case, the more the better determined by the type of pressure pot you have and its factory PSI rating, both of mine are rated for 80 PSI but I have tested them for 100PSI and that is what I use in most of my casts.

There some of these cheap pots that are rated to 40PSI for a good reason, they are made with thin walls a thin lid and little to no reinforcing, the problem is that they can look all very identical from pics unless you know exactly what you are looking for.

Something like this would be suitable and not overpriced, I can not say the same about these guys, they triple the price just because they found out people were buying them for casting purposes and they had no issue because they are strong and made the same way as the one I just suggested before.

There are a few accessories that you will need to exchange/put on a pot like this, those parts are readily accessible and cheap, what they are and what to do, our library will show you many ways to do it, an IAP search will also produce many results.

Another important issue is that whatever the air compressor you will use, will need to have a water catcher/filter, resin and water/moisture pushed into the pot from the air-hose will create problems, guaranteed...!

Best of luck,
Cheers
George
 

Kenny Durrant

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I agree with all the above. I've noticed different people use different amounts of pressure because we do different things. Like mentioned before is it a smooth surface or are there small voids your trying to fill. I use 50-55 lbs. for everything because I don't think too much will hurt the blank so I don't have to worry about adjusting the air. As far as the pot is concerned don't push the limit. Mine is rated for 80lbs so I'm not worried about getting too close to that. Also make sure the pop off valve is still connected and working. I'll pull the ring every so often to make sure it's not stuck. Think about what could happen and prevent it because you might not get another chance. A 2 gallon metal tank with 20lbs of pressure is still a pretty lethal bomb.
 

JPW062

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CA seems reasonable. 80 PSI.
I can budget for that while looking at other options.
 

lorbay

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I agree with all the above. I've noticed different people use different amounts of pressure because we do different things. Like mentioned before is it a smooth surface or are there small voids your trying to fill. I use 50-55 lbs. for everything because I don't think too much will hurt the blank so I don't have to worry about adjusting the air. As far as the pot is concerned don't push the limit. Mine is rated for 80lbs so I'm not worried about getting too close to that. Also make sure the pop off valve is still connected and working. I'll pull the ring every so often to make sure it's not stuck. Think about what could happen and prevent it because you might not get another chance. A 2 gallon metal tank with 20lbs of pressure is still a pretty lethal bomb.

Wanna see a bomb. Check out Curtis Seebacks (aka Turntex) video on his pressure pot failure.
Lin
 

JPW062

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I'm familiar with the results of dry ice in sealed containers.

I hope to be doing production on stamp pens, which won't need much at all, but...

All the fun is in the weird stuff, right?
 

Terredax

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We used a dry chamber vulcanizing autoclave for urethanes and rubbers.
It often ran pressures of 300psi for 24hr cycles. The thing was a massive tank and the lid was removed with a mobile crane. It was constructed from 1/2" steel with double walls for the wet/heat chamber.

The best part, was releasing the pressure. It sounded like a jet. The pressure blew through a 1-1/2" pipe to the exterior.
 
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...
Another important issue is that whatever the air compressor you will use, will need to have a water catcher/filter, resin and water/moisture pushed into the pot from the air-hose will create problems, guaranteed...!

Best of luck,
Cheers
George

This is a very good point and one often overlooked. Those of us that have airbrushed using a compressor are familiar with the need for an inline moisture trap, but it's something not a lot of people know about. Thanks for mentioning this George.
 
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