Casting my first blanks: need help!

[MR2MAN]

I just cast my first blanks using silmar 41. I left them under ~45psi for over 24hrs and the outside of the blanks are still soft and tacky! I used 8-9 drops of cat per 3oz of resin. I used mica powders for pigmentation. They also shrunk A LOT! Any help would be greatly appreciated.

 

[TBCbushings]

The blanks will be tacky after they come out of the pot. You can past cure in the toaster oven on about 120 deg. for about 20 min. The shrining not sure about.. I use 4 drops of MEKP per oz of resin.

 

[truckfixr]

Nikitas beat me to it

 

[MR2MAN]

Will post curing make it completely hard, or will it still be tacky?

 

[MR2MAN]

I put my mold on my wood burning stove (with cardboard and 1/4" plywood as buffer) for over 20min and it's still very tacky.

 

[PenMan1]

You didn't use enough catalyst by about half. GOOD NEWS! put the blank into a toaster oven for repeated 30 minute cycles of 150 heat.

My suggestion is to heat for 30 minutes, out of the oven for 30 minutes, the repeat until the blanks firm up completely.

 

[MR2MAN]

I was wondering about the cat. I saw multiple people using 5 drops per 2oz of resin. I used 9ish drops per 3oz of resin. Did I read wrong?

 

[MR2MAN]

What amount of catalyst is optimal? BTW, my blanks are kinda soft and bendable. Too much heat in the stove? Still very tacky though.

 

[MR2MAN]

What about the shrinkage? My molds are 3/4"x3/4" (I filled them even with the top) and they dropped nearly 1/4"!

 

[PenMan1]

Room Temp, Ambient Temp and Ambient Humidity information would be helpful. Polyester resins shrinks, BUT 1/4 inch is WAY too much shrinkage.

This time of year, here, (shop temp CONSTANT 72 degrees, Ambient Temperature 55 degrees, ambient humidity 45 percent, shop humidity 45 percent) 4 to 5 drops of catalyst PER OUNCE works perfectly with 1/16 teaspoon of Mica Pearl powder per ounce in a 7/8 X 7/8 X 5 inch mold.

 

[PenMan1]

How are you mixing? With 1/4 inch "top" shrinkage, it sounds like WAY too much air being introduced in the mixing process.

 

[MR2MAN]

I mix by hand using a wooden dowel.