Safely heating liquid resin?

[Bizarro Lois]

For a small project, I got some 1:1 resin filler at the hobby shop. It's mainly used to fill in gaps between fiberglass, but the guy at the shop said that it has basically the same ingredients as the 1:1 clear resin you can sometimes get at the craft shop(not the polyester stuff that needs several drops of catalyst). The package says that you should not use it below 75 degrees and that it works best at 90 degrees. I'm in Pennsylvania, middle of winter. How can I safely heat this stuff? I'm thinking about putting the unopened bottles into boiling water. Will that work, or is there something better?

 

[division 6]

Probably not a good idea putting it in boiling water.
If it is like polyester resin I've used it on days ranging in the 60's.
The catalyst will cause it to heat up a bit on it's own.

Others with more experience will hopefully give you better answers since my experience on the subject is very limited.

D6

 

[Bowelrock]

Heat causes the chemicals to react/kick faster.. If your parts A/B are cold it will take longer for the precess to occur but will achieve the same results either way.

 

[Bizarro Lois]

Cool, thanks for the info. That's a big help. I was afraid that it wouldn't cure at all if I didn't heat it. I did roll the bottles around in my hands to take the chill off, but there was no way I was getting them that warm.

 

[hansicle]

I used to do a little fiberglassing from time to time, and realized heat would really help with kicking it off. I used what children have used for years to bake their little goodies.. a 100 watt bulb, just like in an easy bake oven.

You can tent off your piece in some foil, and point a 100 watt bulb at it, and that will give it more than enough heat to get things going..

 

[Bizarro Lois]

The stuff I bought was acutally to cast some small pieces with rubber molds. I poured the resin and let it sit overnight. When I woke up yesterday, a few of the pieces were hard enough to remove from the molds, but still a little tacky. They seem to have cured more thoroughly as of last night. I haven't pulled the rest out yet. A few seemed slightly gummy when I touched the exposed end where I poured. One was extrememly sticky and looked like it had quite a while to go. I don't know why some cured so fast and some still aren't ready to come out of the molds. But as long as they harden eventually, this looks like a good substitute for other resins, if I need it in a hurry.

Edited to add: I was able to pull all but one out of the molds. The sticky one hasn't really changed. How long before I give up and re-pour that one? Some of the other ones had slightly sticky spots, but they're sitting in a warm room, so I'm hoping the tackiness will go away soon.

 

[SD Studios]

Don't screw around with that garbage resin from the hobby shop. I tried it when I was just getting into the hobby (like 150 years ago) and could never get it to work. It is unpredictable junk. Sometimes it sets..and most times...it doesn't. And it smells BAD.

If you are in PA, like me, call John Flint at Polymer Tooling Systems in Exton (610-363-5440) and he can probably ship you an inexpensive sample kit of REAL resin. They stuff the "big kids" use. :lol

I don't know what your budget is, but for $75, you can buy a 2-gal kit of Smooth-On 321. It is a 1:1 mix, has a 7 minute pot life and cures hard in about an hour or two, depending on the size of the casting. Very strong, stable, machine and sands perfectly. GREAT stuff.

I remember trying to use that stinky polyester junk, and all of the problems I had trying to get usable castings...so I feel badly when I see someone else having the same problems.

Throw it away!

 

[Mostly Fantasy]

When I get supplies in mid-winter, I put them in a proofing cabinet OPENED to heat up- heating unopened might rupture the container. I usually heat them at 70-80 degrees F. If it's a liquid that's really pasty from the cold, I'll heat in a microwave safe container in the shop microwave (not used for food), but then have to let it cool down to room temp before using, otherwise, as a previous post said, it'll kick off way too fast to use.

 

[Bizarro Lois]

I don't really know what all the resin types are, but this is not the polyester resin I'm familiar with. The bottles say Epoxy Resin, but I don't know if this means it can still be polyester or not. It's not the stuff that comes in a big can with little dropper of catalyst. It also doesn't smell bad - very little odor in fact. However, the curing is kind of hit or miss. On the batch of heads I made, the main part turned out pretty well, but some of the neck plugs are still a little soft. The one mold that I mentioned previously as still being gooey has not changed at all. Also, on some of the heads, there are little "scars" where a tiny bit remained sticky longer and is still visible even after completely hardening. The results are very similar to another kind of clear 1:1 resin I used from Castin Craft. I'm keeping the ones I've pulled so far, just in case I don't get the alternative before I need this to be finished. I'm also ordering some Smooth-On tomorrow when my paycheck hits. Hopefully it will be here in time. It's a shame - I was really excited at the thought of having an alternative I could buy in a store, even if it was just something to use in a pinch.

 

[terryr]

Putting it hot water should be okay. Years ago I bought some heavy duty epoxy for half price because it had crystallized. The store phoned the manufacturer, who said it would remelt in hot water, just like honey.
I did and it worked.

 

[Mostly Fantasy]

As to the sticky bits on the casting- are you sure you're not scraping unmixed material from the side of the cup? It sounds like a similar problem I ran into using a thicker material- it was hard to mix thoroughly, and I got "streaks" of uncured (sticky) areas on the casting...

 

[TOSPHASER]

As to the sticky bits on the casting- are you sure you're not scraping unmixed material from the side of the cup? It sounds like a similar problem I ran into using a thicker material- it was hard to mix thoroughly, and I got "streaks" of uncured (sticky) areas on the casting...

Once it is set if it is a little tacky you can post bake it in an oven......if you do it in the house your wife will KILL you!:eek I use a small toaster oven in my shop......100 degs. for about 10 mins let cool for a few hours.
no more sticky............also just take the bottle in the house over night to warm before using, less air bubbles when warm and thin!!!

 

[Bizarro Lois]

As to the sticky bits on the casting- are you sure you're not scraping unmixed material from the side of the cup? It sounds like a similar problem I ran into using a thicker material- it was hard to mix thoroughly, and I got "streaks" of uncured (sticky) areas on the casting...

That sounds very possible. The same thing happened the last time I used a different clear resin, which seems to be pretty similar to this stuff.

Once it is set if it is a little tacky you can post bake it in an oven......if you do it in the house your wife will KILL you!:eek I use a small toaster oven in my shop......100 degs. for about 10 mins let cool for a few hours.
no more sticky............also just take the bottle in the house over night to warm before using, less air bubbles when warm and thin!!!

One, I AM the wife:cool However, I rent, and our space isn't that big. So have to be careful doing anything that combines heat, chemicals, and a possible odor. But I do think I'm going to find a way to warm the stuff a little, mix it more thoroughly, and try again with a junk mold.

Oh, and another thing, that cast that was still all gummy never cured. I dumped it out as best as I could. But some of the gunk won't come out of the mold. Is my mold ruined? Is there anything I can do to clean it without ruining the rubber?

 

[Jaded Monk]

Acetone may help clean up the molds. Pulling another cast is the only sure way to clean out the mold. You'll have better success by preheating the molds as well. That Casting Craft is notoriously tempermental. The Smooth-On is much more user friendly.

Cheers,

JM

 

[Bizarro Lois]

I used the tiny bit of Smooth-on that I had sitting around to fill the sticky mold. I was afraid to use it for a good cast, since it was old. But the cast came out of the mold with a lot of the sticky stuff on it, so it looks like I got the worst of it out. I might do another one when my order of Smooth-on arrives, just to make sure. I had to use hand sanitizer to clean the gunk off my hands, so maybe that will work to get the outside of the mold less sticky and easier to handle. Right now I have it sitting in a warm spot to see if anything else hardens and cracks off.

 

[Mostly Fantasy]

If I've gotten a bad cast, Naptha or Prep-Sol helps clean out the mold without damage- it may swell the silicone a bit, so you have to be sure to let it completely dissipate prior to casting again. I've had the same experience with the streaks- once they're there, they're there for good. A bad mix is a bad mix, and it stays that way- best not to waste time trying to fix it.

 

[CustomPropSculptorGuy]

Do it the cheap way, just pour it, let it cure, and then zap it in the microwave, or throw it in the over at 200 for a couple of minutes, then flash it in cooler - not cold - water.

 

[The Kreator]

To get a higher ambient room temperature before working with resins, I store the containers in the bathroom, close up the door and turn on the house heating. By the time the house warms up to 70, the bathroom being a tiny closed up room is 75-80. Works perfectly. And I can just turn on the fan to help ventilate when it comes time to mix and pour. Only disadvantage is less room to work.

 

[Bizarro Lois]

Thanks for the advice on using the hobby shop stuff. I'm keeping it on hand in case I ever need to make a clear item, but I'll be sticking with the more user-friendly resin for the rest of my projects. I couldn't believe the difference when I went to sand one of my pieces made from Smooth-on. It was so much nicer to work with. A new pack of Smoothcast 300 just arrived today, along with some Magicsculp, so life is good.