Pressure pot warming

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cpmech425

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Bellevue. Ohio
I got a pressure pot for Christmas from my wife. Getting set up to start casting some blanks. The weather here in northern Ohio is cold! My shop is heated with a forced air furnace but I don't leave the heat on when I am not working out there. I was thinking about using a heating pad to keep the pot warm after I leave the shop when I have blanks curing in it. What do you think? Anyone doing this? Thanks Brian
 
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Here's a video on cold weather casting. He doesn't directly address heating pads, but there is some discussion in the comments.
https://youtu.be/pdNmeySBOCM

I wouldn't use a heating pad meant for people on this. They aren't intended to be on for extended periods. Most will auto shut off, and if it doesn't, leaving it could be a fire hazard.

There are heating pads available for germinating seed beds, as well as pads to go under reptile enclosures. They'd be much safer to leave overnight. Not sure if they'd keep the pot warm enough without some insulation.
 
cjester said:
There are heating pads available for germinating seed beds, as well as pads to go under reptile enclosures. They'd be much safer to leave overnight. Not sure if they'd keep the pot warm enough without some insulation.
Click to expand...

Interesting video and comments; Maybe make a insulation box to go over the pot?
 
cpmech425 said:
I got a pressure pot for Christmas from my wife. Getting set up to start casting some blanks. The weather here in northern Ohio is cold! My shop is heated with a forced air furnace but I don't leave the heat on when I am not working out there. I was thinking about using a heating pad to keep the pot warm after I leave the shop when I have blanks curing in it. What do you think? Anyone doing this? Thanks Brian
Click to expand...

Why would you want to heat the pressure pot...?

The resin exothermic heat as it starts curing is all its needed for the resin to cure properly, acceleration this process by introducing extra/external heat will most possible mess up the resin by cracking it.

Cheers
George
 
Depending on the temperature the air is at/introduces at prior to applying heat and the pressure you have in the pot, you would have the opportunity to over pressurize and pop the relief valve, so be careful. You can pack a greater volume of cold air into the same space at the same pressure than you can warm air. Once warmed, it will expand some, creating a slight pressure increase.


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i'd do some experimenting first with no heat source to see if you get a proper cure. West sytem epoxy for example, has specific instructions to insure proper curing in colder weather. In other words, don't rely on exotherm.
 
I was going to recommend a poultry water heater but thought the same thing as the heat tape. They kick on typically around 35-40 degrees and kick off around 40-50 degrees as I recall.


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I think for now I will only cast on days that I can cast in the morning and leave the shop heat on all day. I would think after 4 hours in the pot I could take the blanks out of the pot and take into the house. I was trying to think how I could cast after work but was worried about the getting to cold at night as I don't heat the shop when I am not out there. Thanks for all the replies! Brian
 
I got through my first two casts with great results. I normally leave the heat in the shop set at 60 degrees while I am working out there. I set it at 68 degrees for Saturday and Sunday and did a cast each day. I left them under pressure for four hours and they look great! They are sitting in the house now and I will cut the blocks into blanks next weekend. Brian
 
MRDucks2 said:
Depending on the temperature the air is at/introduces at prior to applying heat and the pressure you have in the pot, you would have the opportunity to over pressurize and pop the relief valve, so be careful. You can pack a greater volume of cold air into the same space at the same pressure than you can warm air. Once warmed, it will expand some, creating a slight pressure increase.


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Click to expand...

That is why your pot should have a pressure release valve. :good:


I think the warming is more important for mixing your resins than it is for curing. Some resins, like Alumilit will get thick and hard to pour and mix when they are cold. Warming them to 70+ F will help thin them back out so they can be mixed easier.

I have often thought about making a cabinet with temperature/humidity control simply to store my resins and epoxies in, and possibly my CA's. A consistent temp on these chemicals will prolong their life - assuming they don't get used right away to begin with.

Could be used to keep the molds warm as well as that aids in release if everything is the same temp.
 
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Hey, Glenn, if you give the cabinet thing a shot you may want to look at the stick heaters you can put in a gun safe. I know mine, I think by Golden Rod (even though it is black) always keeps the interior warm and is automatic, so only needs plugged. It was relatively cheap.


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MRDucks2 said:
Hey, Glenn, if you give the cabinet thing a shot you may want to look at the stick heaters you can put in a gun safe. I know mine, I think by Golden Rod (even though it is black) always keeps the interior warm and is automatic, so only needs plugged. It was relatively cheap.


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Click to expand...

Thanks for the tip! I might have look at that, for my guns too lol.
 
MRDucks2 said:
Hey, Glenn, if you give the cabinet thing a shot you may want to look at the stick heaters you can put in a gun safe. I know mine, I think by Golden Rod (even though it is black) always keeps the interior warm and is automatic, so only needs plugged. It was relatively cheap.


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Click to expand...

But is this a kind heater that can heat from the outside. Putting it inside means another hole to seal.
 
chartle said:
MRDucks2 said:
Hey, Glenn, if you give the cabinet thing a shot you may want to look at the stick heaters you can put in a gun safe. I know mine, I think by Golden Rod (even though it is black) always keeps the interior warm and is automatic, so only needs plugged. It was relatively cheap.





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Click to expand...



But is this a kind heater that can heat from the outside. Putting it inside means another hole to seal.
Click to expand...



True. My safe already has an outlet mounted inside. I would tend to think heating a closed cabinet from the inside may be more efficient than heating the same cabinet from the outside, though, even if you will have to plug a hole.


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It would all depend on what type of environment the box would be in, but if it is someplace that can get really cold, you may need a circulation fan as well to help keep humidity to a minimum. Heating the inside of a box while it is -20 in the shed could generate some moisture or condensation. In most cases internal circulation would probably be enough, but in some cases it may need to vent out side.

Any cigar smokers here? A humidor might be something to model by. (or maybe I am getting to anal about it :O )
 
BeeAMaker said:
Any cigar smokers here? A humidor might be something to model by. (or maybe I am getting to anal about it :O )
Click to expand...

Yes you are. ;) But hunidors as per their name do control moisture but they usually add it. They have a gauge and something that carefully meters out moisture. Sort of a fancy sponge.

But in the winter the humidity is pretty low. Right now in my office its 26%. Last week when the weather was around 0 F it was in the teens.

I'm also building a desiccant air drier.
 
Ok I bit the bullet and bought about $15 worth of stuff to heat my pot. (3 small 12v silicone pads, temp control and 12v power supply)

I also do PR and being able to seal it up to keep the stink in is a plus and heat really helps it cure.

Now what would make this really nice is a way to feed the temp probe into the pot. I know I need some sort of NPT threaded pressure gland. I see a bunch that are water proof but not for pressure. Oh and for you Safety Sallys, don't worry I WILL NOT drill and extra hole in my pot.
 
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