Casting Craft Resin from Michaels

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andyk

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Toledo, OH
I usually use the Casting Craft resin from Michaels and don't have any problem. I usually use Testor's Acrylic paint for color and PearlEx powders for some sparkle.

This week I ran into two problems. Both pretty much the same issue, but I'm not sure what I did or didn't do. I was using 1/2" PVC for molds, sprayed the inside like always with PAM, taped the ends. I measured the appropriate amount of resin in a paper cup, mixed my color in (I've never measured that) mixed in some PearlEx made sure it was well mixed. First on I put in approximately 8 drops of catalyst, resin was about 1.5 oz, mixed by hand for 2 minutes and poured into mold. Let it sit 24 hours and removed and it was like rubber, so soft I cut through it with a razor blade by hand.

Thought that maybe I didn't use enought catalyst, so I mixed up another the same way, used approximately 11 drops of catalyst and got the same result. Stored in basement at about 60 degrees and cast in the same place.

I cast one more batch using new catalyst and new resin and am waiting for the se to cure. Has only been about 6 hours so far. The others cured at least 24 hrs.

Any thoughts on what the problem may be?
 
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We had a cold snap (how about TWO FEET OF SNOW!!!) last night and my casting was dead wet. I put it in the toaster oven and it was fine.

60 degrees is just a touch chilly. I try to cast in the morning so I can put the pot by my south-facing window. Cures like a charm. Of course, pretty soon we're not going to have to worry about the coldness any more. I think.

Dale
 
I'm guessing it's a fault of the colorant.

I can't really suggest putting it in the oven, just seems like an unsafe idea. How about a cardboard box with a low watt lightbulb hanging inside, warming the box. You could do this outside.
 
The toaster oven's completely safe. You only have it up to around 120. I have the kind that has an auto shutoff timer for 30 minutes, it works great. Eugene, Curtis, Charles, and probably dozens of other folks use them. I know they do mostly Alumilite but have written in several places that for PR it's a necessity.

PR needs heat to post cure, always. But I've used it when it was too cold at night to cure it initially, then I demold and post cure in the same toaster oven.

I'll let other more experienced casters chime in here, but I'm comfortable with my toaster oven.

Dale

P.S. It also COULD be the colorant, but he said the stuff he uses has worked fine in the past. I use Mixol because it has no fillers or other crap in it. Not sure the same is true for Testor's Acrylic. Also, Andy, you never said what the ratio of PR to catalyst was that you used. That might help.
 
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Yes, I post cure and warm my molds in a dedicated toaster oven and advocate postcuring for both Polyester and Polyeurethane resins.

If I were guessing, which I really am, I would say temperature inhibition or as the OP stated he does not measure the Testors paints he uses as pigments, he has overloaded the resin with the pigment, which can also cause an cure inhibition.
 
Thanks for all the info and suggestions. I think the biggest factor is the temperature. I put them in the oven last nite for a total of about 10 minutes. They are almost cured, one is pretty rigid and the one I cut with a razor blade still has a little flex in it. I will give it another couple of days.

I did state that I used 8 drops of catalyst to 1.5 oz resin on the first and 11 drops to 1.5 oz on the second. On the new batch after reading everything I took a clip light and my magnetic light and left those on the batch over night to keep them warm. 24 hrs takes me to about noon today, this was the totally new resin and catalyst. I will post the results later today.

I like the idea of a warming box for curing. I will look into fabricating something for casting when it is cold.
 
Andy, my apologies, I missed your ratios. The catalyst seems high to me. I do 2-3 drops per ounce. If I would have read that (it was late!) I would have been more suspicious of the amount of colorant you used. Heat is still a critical element, but you can wreck it with colorant. I'm especially suspicious of the Testors, but like Charles said, it's a guess.

You said "oven for 10 minutes". Try it for a half hour, at around 120. If it doesn't cure after that, with as much catalyst as you use, it's probably the colorant. Or, as has been mentioned before, the resin was old when you bought it. I get mine at a wholesale plastics supply and after having gone through 5 gallons, it's way more consistent.

I found from the start this is trial and error! I keep a journal, and write down every recipe I cast-date, temperature, catalyst, resin, results. It works for me.

Dale
 
The few that I cast using all new materials and lights for a heat source turned out normal. At least to touch and looks. Not flexible and they seem to be ready to turn. I will find out later today or tomorrow. I am also going to cast one or two more with the older material and add the lights for heat and see what happens there. I think that it is the temperature issue. We shall see soon...
 
andyk said:
I usually use the Casting Craft resin from Michaels and don't have any problem. I usually use Testor's Acrylic paint for color and PearlEx powders for some sparkle.

This week I ran into two problems. Both pretty much the same issue, but I'm not sure what I did or didn't do. I was using 1/2" PVC for molds, sprayed the inside like always with PAM, taped the ends. I measured the appropriate amount of resin in a paper cup, mixed my color in (I've never measured that) mixed in some PearlEx made sure it was well mixed. First on I put in approximately 8 drops of catalyst, resin was about 1.5 oz, mixed by hand for 2 minutes and poured into mold. Let it sit 24 hours and removed and it was like rubber, so soft I cut through it with a razor blade by hand.

Thought that maybe I didn't use enought catalyst, so I mixed up another the same way, used approximately 11 drops of catalyst and got the same result. Stored in basement at about 60 degrees and cast in the same place.

I cast one more batch using new catalyst and new resin and am waiting for the se to cure. Has only been about 6 hours so far. The others cured at least 24 hrs.

Any thoughts on what the problem may be?
Click to expand...
Lack a heat really affected my pours. I'll bet you need warmer conditions. Thanks for the tip on PAM.
 
Some more info...

One thing that you must realize is that the PR Resin will harden on its own if you leave it out and the solvent evaporates. The catalyst speeds up the process with heat...If you have the right amount of heat, it will cure quickly...Very quickly. Humidity also slows the evaporation rate of the solvent.

Trial and Error is needed. I have a 10$ toaster oven that I use to finish curing my casts, if necessary. Usually, I mix em up...pressurize for 24 hrs and its good to go...

Here is what I do when working outside. Mix and pour, warm the pot with heater or halogen light(when really cold), put under pressure and bring in the house. No worries about humidity, the light dries the air in the pot. The temp of the house keeps the pot warm. No smell because no air leaks into the house as long as all fittings are tight.

Grub32
 
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