I have research a bit and found that there seems to be a rng factor given to your character either during login or every time you change instances. I noticed this through constant farming and refining raw materials that some days I receive more purple/gold temps/resins/rosins. I also have seen many videos and heard many times from other gamers that you want to reset the refining table after a few raw 10 stacks are refined if you do not receive a gold or purple. IDK if anyone has a definitive answer, but if you do please post it here and save many of us the trouble of refining 1000 stacks and getting 1 temp/resin/rosin...
"Stendarr's mercy be upon you, for the vigil has none to spare."