Sample of a face cream was created and divided into two containers for stability test, one at room temperature and one at 45oC. The one at room temperature remains unchanged after 2 months while the other one darkens in color and thickens as well. Both had PEG-80 and xanthan gum added. Does this result imply that the product will eventually darken in color and thicken up over time or will this only occur under high heat? The one that stays in room temperature is totally fine, no changes since mixing. Scent, viscosity and weight remain the same.