I have found that the Omphalotus olivascens can be sensitive to really hot water. I used hot tap water which was around 100 degrees, added the ground mushroom and a glug of vinegar to help coax the color. I cooked it for about an hour at 140 degrees and then added the fibers. One thing I have done in the past, but not for these studies, is put in fiber that has not been mordanted. It works! The color is light fast but it shifts over time from a purple to a red brown without the mordant.