Plastisol yellowing.....

[Water]

My last box is "discoloring" around 320 degrees. I rotate and add stabilizer to no avail.  It is leaving the plastisol an orange color, looks great until it reaches the 320 degree mark and boom there it goes. I've tried stabilizer and no stabilizer, driving me crazy.

-I cook it on 35 second intervals, usually takes 3-4 cycles to get to temp on my 900 watt MW.
-stir on the second and last cycle

I don't know what I'm doing wrong, any ideas?

[ctom]

The plastic is burning. To hot. How are you measuring the temperature? Or the plastic is bad. I'm betting on the temp being wrong. If you have a thermometer, which type is it, infrared or digital? Most all here use the digital and if you do as well just be sure to read the temperature from the middle of the plastic mass and not with the probe on the cup's bottom or touching the glass sides. The hottest plastic is smack in the middle of the cup.

Are you setting the cup directly on the glass rotisserie in the microwave? Try cutting a piece of corrugated cardboard large enough to cover the glass and set the cup on it during cooking....microwaves can have and develop hot spots and the cardboard helps buffer against them.

[andrewlamberson]

Also..make sure your plastic is completely mixed....every time you use it.

[Water]

Thanks guys, will try the cardboard. I'm using a digital thermometer.

The funny thing is with a little blue and black flake it makes a beautiful color bait. I didn't want to waste it.

[biglewers]

I had the same problem with the last few box of the CCM plast I did have.  I didnt know why it was burning like it was.  I had done nothing and hadnt changed anything of the way I do things.  I loved the plastic but i switched over to another plastic.

[ctom]

Who's plastic is it? I don't see where you say in your post. If it comes from Do-It, call the company and have them help you work thru the problem directly. All too often commercial squirters working with larger volumes heat their plastic different from how us hobby minded guys do. How the plastic is cooked makes a huge difference but you indicate a microwave and show a cup so you're pretty much on the page of use hobby guys. The guys at Do-It can work with you if you have a Do-It product.

"Also..make sure your plastic is completely mixed....every time you use it"....per Andy

Regardless of the brand, give the jug or box or whatever the plastic is in a good shake before you use it especially if its been sitting a while or you don't know how long its been since it was mixed good.

Maybe try mixing and cooking a smaller batch or two to see until you figure things out so you aren't wasting plastic. I have noticed that I will have more issues with any plastic in a microwave when larger volumes are being worked with and have settled for 4 ounce batches pretty much.

[BigFoot_158]

My last box is "discoloring" around 320 degrees. I rotate and add stabilizer to no avail.  It is leaving the plastisol an orange color, looks great until it reaches the 320 degree mark and boom there it goes. I've tried stabilizer and no stabilizer, driving me crazy.

-I cook it on 35 second intervals, usually takes 3-4 cycles to get to temp on my 900 watt MW.
-stir on the second and last cycle

I don't know what I'm doing wrong, any ideas?

I am a big fan of digtal probe type thermometers. Second I would stir after every cycle. And maybe drop your time to 25 seconds and then stir. Just think of slow and steady wins the race.