I use Gamblins "Gamsol" 100% pure odorless mineral spirits (OMS) for my washes because I find it holds the colors better than other products I’ve used although Turpenoid is a close second choice and it is less expensive than Gamsol. Note: I start working my wash in the lightest areas and continue into the darkest value areas. This allows the colors to remain more color correct although the purpose of the wash is to TONE THE PAPER so you don’t have gaping white areas on the finished surface. This isn’t a watercolor painting, thus white areas are not required.