PR colors blending in toaster oven??

[Tim'sTurnings]

I have been trying to use contrasting colors in my PR pen blanks. I let them set for 10-15 min. till they start to thicken. I then add the main portion of colored PR to my mold, let set a couple more minutes, then add the smaller amount of contrasting colored PR to the mold. I swirl it around until I have the design I want and then stop. I place the mold in the toaster oven at about 190 degrees for 25-30 minutes. When I take it out it seems the colors have blended somewhat, not like the way I put it in the oven at all. I even have had some that the contrasting color drifted to the top of the blank.

I am using the suggested amount of hardener, (for Castin Craft brand). I sometime add an extra drop. For pigments I mainly use Pearlex powdews but I have started to use Testor's model paints because I have had good reviews with them.

Should I stop using the oven?? Or should I wait, I don't know how many hours until they get rigid before I "toast" them.

Any comments will be appreciated.

Thanks, Tim

 

[jdoug5170]

Tim, I may be wrong here, but I think that 190 might be a little too high.

I'm in Oregon where the temps are 55-65 these days and therefore I put my P/R castings in a converted refrigerator/hot box that I warm to about 75-85 and I've had pretty good results. I just use a light bulb in there for heat generation. It is sure nice to be able to cast and play in the same day now.

Doug

 

[hughbie]

i have my toaster oven set at 150.....you really don't need the extra heat.....i run my oven at 15 minute cycles....and i do about 3 cycles.....then let it drift to room temp......no problems on my end

 

[Glass Scratcher]

190F is way too high for curing or postcuring any casting resin. Under normal circumstances an hour at 125F - 130F would be adequate for postcuring.

You don't need to start postcuring the resin till the resin has cured (or unless your MEKp has gone dead, but that is a different post). Postcuring provides enough external heat to give molecular energy and molecular motion for the resin to fully crosslink and thermoset.

If your resin is hardening, leave it for 6 to 8 hrs, or until it is firm (solid to the touch). Afterward you should postcure, at the temperature close to the deformation temperature of your resin. I don't know what the temp is for the Cast'n Craft resin. Cast'n Craft resin is made by ETI, a call to them should answer that.

 

[Tim'sTurnings]

Thanks for the comments. I will take all into account. I will lower the temp in my oven as recommended if I don't need it that high. I will try to let the mixture set for 1-2 hours before the "postcuring" but I don't want to wait 6-8 hours before putting them into the oven if I don't need to.

Again, thanks for the replies.
Tim.

 

[hughbie]

tim, i did a demo of casting at our last meeting. i mixed and poured.....let it set for about 1 hour then put it in my oven for another 1 1/2 hours.....it worked fine....all at 150

 

[td]

"When I take it out it seems the colors have blended somewhat, not like the way I put it in the oven at all. I even have had some that the contrasting color drifted to the top of the blank."


Tim,

We'd all have some pretty darn exciting blanks if we could "position" our colors and then control the exothermic reaction to not move any of it. Fact of the matter is in order for the cross linking to occur the MEKp "kicks off" the exotherm and then we are at the mercy of the color kings. If you stand and watch the process you'll understand why your pattern looks different when it hardens. It's actually very interesting..... to some. Part of the intrigue is figuring out your timing and pours!

It's all a learning process and the more you cast the more patterns, ideas, disasters and finally.... over-the-top GREAT BLANKS come to you.

Happy Adventuring!

 

[Paul Downes]

I commonly mix 2-4 colors. I wait for the resin to start to gel and then mix them up and manipulate the resin in the mold. I have used gelling agent to gel one color and leave it out of the other(s) You have to be careful to catch the gel just as it starts and be quick to add the other colored resins, or you get a stratified blank.

Another thing I have been experimenting with is adding less MEK to one color so that it gels at a slower rate. This helps keep some color separation.

I have a radiator in my shop that is around 180 degrees. I wait for the resin to gel and then set the mold on the radiator until the resin shrinks away from the sides of the mold. I then just pop it out and set the block on top of the radiator to cure. Seems to work just fine.