THERMAL STABILTY CURVE
You can observe two regions - operating region and degradation region in the graph. If you maintain the material in operating region moulding can be with out silver streaks / gas bubbles. If the condition of material shifts to degradation region, then you must expect silver streaks / gas bubbles in the moulding.
During the production run, varying residence time can vary the colour shade, if the pigment used is sensitive to residence time.
Also see Residence Time