Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

Hello! Ever have a large number of molds you want to cast, but you can only pour "X" amount of 2 part heat cure resin and mix it before it hardens too fast?
Well almost no more!

Disclaimer: I tend to ramble, so bold is important, the regular font is for pleasure.

I got this idea from a mythbusters episode where they were testing myths about how to quickly chill a warm beer to the perfect drinking temperature and it got me thinking, what if you used this method to cool resin?

You will need: Ice, 2 empty sacrificial containers (bowl, jug whatever. Doesnt have to be huge), salt and water.
Not to mention heat cure resin in their own containers.

I prefer Alumilites resin, but I also have smooth cast 300. Any heat cure resin will do.
While I was using smoothcast 300, I could do a large batch of molds, on average, I would use about 15cc of each part (30cc together) and do about 6-10 molds at once with an oral syringe before the resin would heat up and harden fast than I could pour it. Alumilite on the other hand, although its cheaper, easier to paint, has a better container, and better directions cures too fast to do a large batch size. Without using the method that I'm going to layout, I could only do 7.5cc of each part, or 15cc together before the resin cures faster than I can use it, and I can get only generally 2 molds, maybe 3 if they are small and im fast.

Method: Put ice in the sacrificial bowls, pray to the machine god, pour some salt (I used mortons sea salt cause it was handy, but salt is salt) into the bowls where youll be pouring water into them. How much you ask? Good question. Next, pour water into the bowls leaving room for the resin containers to displace however much water they displace in the bowl (quick way to figure this out is fill the bowl to the brim then shove one of the resin containers into the bowl. The water that slops over the edge is how much you shouldnt have put in it)
You dont want to submerge the containers. I put mine in to the level of the liquid in the containers.

Now take the next 5 plus minutes while the resin chills to make sure your workspace and materials are prepared. Go over your checklist. Do you have the molds you want to pour ready? Do you have extra molds ready for the magic thats about to happen? Is your air compressor properly hooked up to your pressure chamber? Are the machine spirits properly appeased? Is your syringe clear and ready to suck some resin? (I always forget that one psh)

Ok, its time, shake your part A and part B really well. Now notice when you pour they are more sluggish than just sitting at room temperature, that perfect! This is it, pour MORE than you are used to in your measuring cups. I do 7.5cc at room temp and to test it I did 10cc (for a total combined of 20cc) which usually heats up and hardens before I can get through half of it.

Doing this, chilling it, at 10cc a part I was able to do 8 molds of alumilite before my syringe got hot! Thats 6 more molds than usual!

How does this work? Mix together a batch of resin and just let it sit. If you notice, the center hardens before the edges do. Why? The chemical reaction going on in the center of the resin does not have to over come the temperature of the container so cures faster. On the other hand, the edges of the resin batch have to over come the temperature of the air and the sides of the mixing container (in other words, its losing heat to the outside).

Alumilite says to decrease curing time, bake your molds in the oven before pouring resin into them, so that the resin does not have to over come the temperature difference.

This difference is what this cooling method exploits. By decreasing the temperature of the resin, it has to overcome that lowered temperature, then it has to overcome room temperature before getting to its cure temp.

Hope this wasnt too ramble mamble and helpful!


Now in! Results from the mythbusters episode I speak of in a link format. http://kwc.org/mythbusters/2005/03/mythbusters_cooling_a_sixpack.html:

yes, lets all bake toxic waste in our kitchen, sounds like a great idea.

kb305 wrote:
yes, lets all bake toxic waste in our kitchen, sounds like a great idea.

Er... what? Where does this post refer to toxic waste? Or kitchens, for that matter?

I'm assuming you're talking about the reference to heating moulds in the oven. Which doesn't mean baking anything toxic in your kitchen oven. I have a little portable oven that I use for curing Sculpey. A similar oven could just as easily be used for moulds without using your kitchen device.

And moulds for resin casting are generally made from silicon. Which is inert. They make baking trays and cake tins out of the stuff.

 insaniak wrote:

kb305 wrote:
yes, lets all bake toxic waste in our kitchen, sounds like a great idea.

Er... what? Where does this post refer to toxic waste? Or kitchens, for that matter?

I'm assuming you're talking about the reference to heating moulds in the oven. Which doesn't mean baking anything toxic in your kitchen oven. I have a little portable oven that I use for curing Sculpey. A similar oven could just as easily be used for moulds without using your kitchen device.

And moulds for resin casting are generally made from silicon. Which is inert. They make baking trays and cake tins out of the stuff.

well, he said bake your molds in the oven.

are you 100% sure mould rubbers are inert? what about the resin chemicals getting into or onto the rubber?

kb305 wrote:

 insaniak wrote:

kb305 wrote:
yes, lets all bake toxic waste in our kitchen, sounds like a great idea.

Er... what? Where does this post refer to toxic waste? Or kitchens, for that matter?

I'm assuming you're talking about the reference to heating moulds in the oven. Which doesn't mean baking anything toxic in your kitchen oven. I have a little portable oven that I use for curing Sculpey. A similar oven could just as easily be used for moulds without using your kitchen device.

And moulds for resin casting are generally made from silicon. Which is inert. They make baking trays and cake tins out of the stuff.

well, he said bake your molds in the oven.

are you 100% sure mould rubbers are inert? what about the resin chemicals getting into or onto the rubber?

Ah, if you are too fearful to even use resin (please dont tell me you think somehow it was said while in the oven pour the resin into the molds), why are you worried?

Furthermore, my entire post is about making molds cure slower. The mold in the oven tidbit was just that, an interesting tidbit. Im actually surprised the first person to say anything at all latched onto the smallest little sentence in the post.

Didnt you know theres a ton of toxic stuff we (or at least those of us that dont live in a (nontoxic) plastic bubble) are exposed to on a daily basis? Like sunshine?

Warming a silicon mould in the oven is not the same as baking them.

You warm them if you have a slower cure exothermic resin that you want to go off faster (kick-starting the exothermic reaction).

The natural corollary to this would be to chill it if you want to slow its curing down. Or in much of the US/Canada in winter - do it outside.

These are all pretty common sense ideas to anyone who has a modicum of knowledge of silicon moulding rubbers, resin and exothermic chemistry.

kb305 wrote:
well, he said bake your molds in the oven.

Yes... and as I just pointed out, that doesn't mean doing it in the kitchen.

are you 100% sure mould rubbers are inert? what about the resin chemicals getting into or onto the rubber?

Being inert is one of the defining characteristics of silicon...

And if you're using a mould release agent (which you should be) the residue from the resin from previous casts is going to be extremely minimal.

But, again, if you're not confident about using your kitchen oven, just use a different oven...

Also, heres a link: http://alumilite.com/FAQ.cfm#27

Look under misc. for the very first bullet.

Basimpo wrote:

kb305 wrote:

 insaniak wrote:

kb305 wrote:
yes, lets all bake toxic waste in our kitchen, sounds like a great idea.

Er... what? Where does this post refer to toxic waste? Or kitchens, for that matter?

I'm assuming you're talking about the reference to heating moulds in the oven. Which doesn't mean baking anything toxic in your kitchen oven. I have a little portable oven that I use for curing Sculpey. A similar oven could just as easily be used for moulds without using your kitchen device.

And moulds for resin casting are generally made from silicon. Which is inert. They make baking trays and cake tins out of the stuff.

well, he said bake your molds in the oven.

are you 100% sure mould rubbers are inert? what about the resin chemicals getting into or onto the rubber?

Ah, if you are too fearful to even use resin (please dont tell me you think somehow it was said while in the oven pour the resin into the molds), why are you worried?

Furthermore, my entire post is about making molds cure slower. The mold in the oven tidbit was just that, an interesting tidbit. Im actually surprised the first person to say anything at all latched onto the smallest little sentence in the post.

Didnt you know theres a ton of toxic stuff we (or at least those of us that dont live in a (nontoxic) plastic bubble) are exposed to on a daily basis? Like sunshine?

After looking into it a bit awhile back, I am too fearful.

niosh says filters arnt good enough when working with isocayanates, you need a fresh air supply. isocayanates are odorless (no warning signs). the MSDS says basically "to practice excellent hygiene when using it. shower alot aftering using resin, dont rewear clothes until washing them". so basically it sticks to everything.

sounds a little worse than sunshine to me.

ill bow out here, sorry if i hijacked the thread.

Don't use superglue then!

Having done a lot of moulds I've never thought of cooling the resin! A very useful tip by the sound of it and one I'll try and use next time I do some casting.

If you are just warming the molds (silicon) then all is well. I have done it in the past, in my kitchen oven where all the cookies are baked! (MMMM COOKIES!)

If you are worried about silicon molds being baked, then stay away from moms cakes and muffins. Silicon baking and cooking items are all the rage now because of their non stick quality. Betty Crocker and Tollhouse are evil, true, but only because they make us fat gamers, not because they make us cancer patient gamers. Do your research and calm down a wee bit.

Life is gonna kill you anyway, no sense in sweating the little things before it gets you.

Forgive my ignorance here, but could you not just stick the resin in the fridge for half an hour before mixing etc?

Of course! That works too I just forgot to put it in in my excitement. I was actually contemplating purchasing a mini fridge for my garage workshop that I could store my resin in, I just forgot to mention it. Personally though, I wont store my resin in my kitchen fridge. Its one thing to handle and be around this stuff (I think its safe) and its another to ingest it, on purpose or accidentally.

Also, the salted ice water trick will lower the temp of your resin to what I estimate to be about 38 degrees in FIVE minutes. How long would it take a fridge? Half an hour? More? Im going to put a link in my OP that leads to the results of the episode, which actually my memory shows I didnt remember it as great as I thought I did!

 Grimstonefire wrote:
Forgive my ignorance here, but could you not just stick the resin in the fridge for half an hour before mixing etc?

Yeah, working with carbon fibre/epoxy resin composites we'd often do that to increase the working time. Some resins you need to keep in the fridge just to stop them curing, and it can even increase the shelf life of a resin if you store it in a fridge.