Having issues keeping plastic clear

[Billmo]

OK.. I know its me doing something wrong but I dont know what... 

I heat my initial plastic to 335-350 if its in that range im good.. I add my glitter usually red and my hot plastic is no longer clear with red flake, it starts to yellow like its buring the glitter...  is my plastic too hot? should i add glitter when its cooler and then finish heating? should i get another infra therm to verify my heat?  its usually so bad i end up throwing it all out, never end up shooting it or reheating it..   I have tried adding the CCM heat stablizer when i first heat my plastic,  but i still end up with yellowing plastic. 

[andrewlamberson]

First off...is it CCM Plastic? That is what I use and I always take it to 350 degrees.

2nd: You need a good quick read digital thermometer (NOT a IR Thermometer which only reads the "skin" temperature and are notorious for giving different readings based upon the color of the material. Here's a link to the thermometer I use (and why)...the good news is that it is cheap!

 http://www.caneycreekmolds.net/index.php?topic=1182.msg7170#msg7170

3rd: How many watts is your microwave ....and are you heating it on high? The molecules in anything that is being microwaved continue to vibrate (and heat up) for over a minute ...thus you might stop at 350...but your temp continues to climb....

 http://www.fsis.usda.gov/factsheets/microwave_ovens_and_food_safety/index.asp

So... I would bet you are heating the upper layer of your plastic to 350 (according to your IR thermometer) and the center is MUCH hotter...and continues to get hotter for the next minute or so...and then poof...burnt plastic! Just for grins....measure the temp of your plastic the way you have, then stir it..and measure again...

[Billmo]

1. Yes CCM is all I use thanks to reading everyones post on this forum
2. I am using an IR so I think I will make that little investment and get a digital like the one you posted.
3. 900watt an yes its on high...  First thing I do when I pull the plastic out of the micro is stir. This way I know(or thought I knew) that I was getting even heating throughout the plastic. 

If there is anything I have learned from the pro's on this board is to check, check and triple check temp. That seems to be the biggest hurdle. 

So im going to get an insta read digital therm and see what happens from there... 

[pjmcla]

Are you heating at one shot from cold to 350?  If so I bet you are getting some scorching here from uneven heating.  I never heat more than 1:15 with a stir from cold & a max and 30 sec. from there on with stirring.  Now; if the plastic is clear right before you add glitter; then turns yellow right after; It might be the glitter.   Who's glitter is it?  I had some silver that turned my clear plastic a light green; and have a purple that will turn clear plastic greyish as well.  These are name brand glitters ( non caney creek ).   

[Billmo]

4oz plastic is heated for 1min then stirred and heated more as needed with stirring
8oz plastic is heated for 2 min then stirred and heated more as needed with stirring
I dont do more than 8oz at a time since I am new to this I dont have enough molds to justify heating up more than that at once.  I am using a NON CCM glitter in this case, I am using M-F.. I do have CCM red but in the small .015 flake which is too small for this application.. 

I guess instead of wasting you guys time with question I should try it with CCM red and I should also try other color glitters...         

[Jason]

If you have time tomorrow let's hop on the phone and talk through this. It should be something simple. Did you watch the video at the bottom of the plastic page?

Jason