Heating the board prior to the mount can remove some moisture. This may or may not help in keeping the board flat after the mount. That may have to do with ambient humidity as well. I've had boards curl with too much heat from the car, I have had them curl a bit due to high humidity changes as well. They didn't always return to their original flatness. Robert Hall www.RobertHall.com On Thu, Oct 14, 2010 at 4:04 PM, Tom Schofield <tomschofield@xxxxxxxxxxx>wrote: > I was taught to preheat the mat board by putting it in the press before > mounting it. > > I suspect that mounting in the Ansel Adams tradition used higher temp > tissue with the fiber based paper. Maybe the problems are more endemic to > the lower temp tissues, but I do not consider myself an expert! > > Tom > >