If a pigment does not 'bleed' into oil, it is said in the trade to be 'fast to oil'. A text I'm editing says that pigment A is 'faster to oil' than pigment B. This sounds very strange to me, and I can find no examples anywhere. However, 'more fast to oil' sounds just as strange and gets no google hits. Now if this were 'lightfast' I'd say 'more lightfast', but 'oilfast' doesn't seem to exist, though I'm tempted to use it nonetheless.and say 'more oilfast' Any suggestions for the comparative?