Dry Mount Problems...Please Advise!
I've been dry mounting my prints for several years now, and use Beinfang BufferMount tissue in a Bogen press large enough for 16x20 prints. (I only rarely mount prints larger than those on 11x14 paper.) I heat the press to the nominal 170ish degrees, and put the print in for a minute and a half. I preheat the mount board and print separately for a minute or so to be sure they're dry, let them cool, and then put them in the press. The studio is usually not humid at all, and in fact is quite arid in the winter. They usually come out quite well, although there are sometimes a few bubbles that I press out with the tacking iron.
The problem that has arisen is that several boxes of mounted, framed prints that have been stored in the garage are showing significant bubbling that hasn't responded well to re-pressing to remove. Also, some prints that have not been framed, but kept in boxes that were open for a while in our bedroom that was being humidified at night with a humidifier have showed significant bubbling as well. However, mounted, framed prints from the same sessions that have been on the walls since being mounted are fine.
What's wrong? Is there a limited range of temperatures that prints should be stored in? A limited humidity range? What if someone buys a mounted, and framed print for their vacation home that isn't heated in winter, or air conditioned in summer? Am I doing something wrong with my process?
I'd greatly appreciate some advice as I have a show going up at the end of March and don't want to offer prints for sale that may not remain in the condition in which they were purchased. Thanks for your help in advance.