Painter,
I usually make 32 oz. batches of light colors in my presto pot. I put the plastic in the pot with four tsp of heat stabilizer and turn on the stirrer and the pot. It takes 20 to 30 minutes to get to pouring temp. Then I add my colorant and flake and go. This allows me to empty the pot faster befor the plastic has a chance to yellow. For dark colors I can make 64 oz. batches.