Here is a more detailed explanation of what's going on and why stabilizer is important. Your plastic has stabilizer in it, so this really applies to reheats or prolonged heating cycles. It's important to thoroughly cook your plastic (350+ all the way through), failure to do so can cause your baits to cloud up...
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When you cook your plastic it is actually changing what it is at a molecular level. Chlorides (the "C" in PVC) want to attach themselves to something. In the absence of a heat stabilizer, it will attach itself to the vinyl. This is what causes yellowing. With heat stabilizer present it attaches itself to it - thus preventing yellowing. Each molecule of heat stabilizer can only be attached to one time. That is why at some point you may need to add more.
With that said, if you are using Crystal Clear there is no way you need to add stabilizer on the first or second heating - even if you are taking it up to 420 degrees. I test this on a regular basis (every batch). It is not until the third heating at this extreme temp is additional stabilizer needed. Under less intense circumstances (not exceeding 360 / 370) you can easily get 3 - 4 heatings out of it (I will normally add 4 drops of stabilizer to a half cup on the 4th heating if I'm abusing it). Disclaimers - this is with my microwave, using all CCM products (they are designed to work together). There are literally thousands of different stabilizers to choose from, we use a blend that we have found to be optimum for what we are doing.
Here is an easy test, go through your process with clear plastic. Make sure and roll the box over a couple times first. See if your plastic changes. Then try it with colorant (add it before heating). Then try it with glitter. Then try it all together. If you keep your temps reasonable you will be able to reuse all the plastic so there isn't any waste. This will give you a good idea what each component is doing so you can identify where the problem is.
A final note on stabilizer... Adding to much when it's not needed will produce additional smoke and smell. I haven't seen it make a bait softer or harder (I'm sure if you used it like softener it would do something???), but I have seen where to much will make a bait more brittle.
Hopefully something in here is helpful.
Jason