Lowest twmp for casting polyester resin?

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TattooedTurner

TattooedTurner

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I'm sure this has been asked many times, but I'd like to hear from those of you with actual hands on experience. What is the coolest temperature you cast poly resin at (I use Silmar 41) with acceptable results? I don't like to cast below 70F, and preferably 74+, but we're down to the 60s here in the desert, with my garage cooling down to the low 50s at night. I want to cast some blanks to use up my resin but not if the results aren't satisfactory. Can I cast in the morning and leave them in the pot for 24 hours even though they'll get cold for the night? It stays warmer in my garage at night and I'm not about to set the pot in the sun during the day then move it to the garage at night while it's pressurized. I take no chances with my cheap HF pot. I let my blanks fully cure for at least 2 weeks before turning, I just want to make sure they'll set properly before removing from the pot so I don't get any air voids. Any help would be appreciated. FWIW I cast in 1" OD pvc tubes, blanks are about 0.8" diameter.
 
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buy a heating pad and affix it to the side of the chamber. place a cup of water in the chamber and let it go for a few hours then measure the temp of the water. adjust the heating pad controls as necessary. omit the cup of water if you have a thermometer with a remote probe.
 
I've cast silmar in the 40's in my garage. But it required me to heat the resin before I cast. Usually took a day or so to fully cure
 
jcjc said:
buy a heating pad and affix it to the side of the chamber. place a cup of water in the chamber and let it go for a few hours then measure the temp of the water. adjust the heating pad controls as necessary. omit the cup of water if you have a thermometer with a remote probe.
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OP just be aware that every heating pad I've purchased for my wife, its a lot, in the past 10 15 years has had an auto turn off "feature" good for humans not for casting.

Now that I type this, heated throws like blankets usually don't have this feature.

Also if you are buying one you need to get one soon. In a few weeks, at least in south west Pennsylvania, spring merchandise will start hitting the shelves.
 
I cast at any temp. Just Warm your resin (before you add the catalyst) and your tank and molds prior to pouring, and then place it in a spare room away from everyone in the warm house for curing.

Think of it like an easy bake oven for kids...Get you some electric clamp lights and place your empty molds in the tank and position one light over the tank shinning down inside it for 20 or so minutes prior to pouring. Do the same with your cup of resin in a small box lined with aluminum foil. Just don't get it too hot or it will cure too quick when you add the catalyst. After the tank is sealed and inflated, place it in a room away from people in the house. I place mine in a spare bedroom in the house near the heat duct for about 20 hours. then just take it back to the shop to open.

If you don't want to move the tank after you pressurize it I guess you could always position a clamp light shining closely to the side of your tank to warm it up as long as you were in the shop with it.
 
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Thanks for the help. I'll bring the pot inside to come up to room temp and warm the resin first. I was actually thinking of putting the pot/air compressor in the laundry room, but on the outside chance it blows I'd rather keep any damage contained to the garage.
 
Cold temps are fine for resin storage, you just don't want to pour it while it's cold and thick. It makes it hard to for the air bubbles to rise up and out. I usually keep a can of resin that I'm using upstairs where it's warmer but the rest in the cooler shop. I've never had a problem but I can use a gallon in about two weeks or less. I've had them 6 months old with no problems but prefer to use it within 3 or less months so I continue to get fresh resin. I don't bring my pot up until it's closed and sealed. You can also warm the compressor air inside the tank with a clamp light before you pressurize the pot. Then warm air is going in. Good luck and happy casting!
 
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My shop is not heated. Below about 60 degrees I use an old crockpot - I got one at Goodwill. I turn it on and let it get warm, then mix the color into the resin, and warm the colored resin up before mixing in the catalyst. If I'm doing embedments I warm those up as well. I let the blanks bake for an hour or so, after which they're fine. In the summer I don't need to do this.
 
Thanks for the additional replies.

I really like casting in the summer here when the temps are 110+. The resin is thin, any air bubbles rise to the top almost immediately, and it cures fast with the pot sitting out in the sun. I demold in 4 hours with no problem so I can do 2 batches in a day and sometimes a third, but I have almost no experience casting when it's cold.
 
PR should set just fine anywhere from 60-80F ambient temperature. Below 60, you may need to warm the resin and/or add more MEKP. Above 80, you may need to cool the resin and/or use less MEKP.

Too cold a cast may take a long time to harden. Too hot a cast may result in brittle blanks.

I hope that helps,
Eric
 
Sylvanite said:
PR should set just fine anywhere from 60-80F ambient temperature. Below 60, you may need to warm the resin and/or add more MEKP. Above 80, you may need to cool the resin and/or use less MEKP.

Too cold a cast may take a long time to harden. Too hot a cast may result in brittle blanks.

I hope that helps,
Eric
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Thanks Eric. I've got hot temperature casting down since it approaches 120F here during the summer, but I have almost no experience casting PR in cooler temps. I switched to Alumilite last winter, but I'm just not happy with the depth of shine - or specifically the lack thereof - that I get compared to PR.
 
Alumilite has its advantages and purpose depending on what your casting. An easy fix to the lack of shine is a CA finish. It shines beautifully then.
 
Sylvanite said:
PR should set just fine anywhere from 60-80F ambient temperature. Below 60, you may need to warm the resin and/or add more MEKP. Above 80, you may need to cool the resin and/or use less MEKP.

Eric
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Interesting. I use a crockpot set on low. I have a meat thermometer in there. I'm just restarting casting after 2 years of not doing any, and when I did cast, the temps were 110<>130. My experience is a very slow set at anything below about 80 degrees.
 
JohnU said:
Alumilite has its advantages and purpose depending on what your casting. An easy fix to the lack of shine is a CA finish. It shines beautifully then.
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Alumilite definitely has its advantages, and it's a breeze to turn. I can do a good CA finish, but my favorite thing about turning something from resin is that I don't have to, it ranks pretty low on my list of things I like to do in the shop.
 
crokett said:
Sylvanite said:
PR should set just fine anywhere from 60-80F ambient temperature. Below 60, you may need to warm the resin and/or add more MEKP. Above 80, you may need to cool the resin and/or use less MEKP.

Eric
Click to expand...

Interesting. I use a crockpot set on low. I have a meat thermometer in there. I'm just restarting casting after 2 years of not doing any, and when I did cast, the temps were 110<>130. My experience is a very slow set at anything below about 80 degrees.
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I agree. I'm used to casting in high temps and I know just when the resin is at the stage that I like for pouring the blank. Below 80 it feels like I'm sitting there way too long.
 
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