I had the same issue with black coming out brown, i lessened the time to 180 from the 220 i was told and black is now as it should be :) Is your paper turning yellowy, i understand that is another sign of overcooking :). I don't dip my mugs after printing them, i have a wire rack under the heat press table with a regular desk fan aimed down on the mugs. They cool pretty quickly and i've not got bowls of water around or wet mugs to dry off before packaging. Could do with a bigger workspace though as my feet get cold as well :)