Malinda Welte , Jul 01, 2001; 04:10 a.m.
Most of the time, photographs are mounted to a mounting board, usually acid-free foam board or mat board if there isn't room in the frame. An alternative to the linen tape is acid-free artist tape, I think it's a little less expensive. I also use mylar mounting corners. My framer friends advocate dry heat mounting for photos that aren't limited edition prints that you paid a gazillion dollars for. They won't buckle with a humidity change and it's archival. You will be fine either way, though. I do highly recommend using an acid-free rag mat, I have had photographs discolor under regular Crescent mats.
Q2 You hinge the mat and mount to keep them from shifting while you are mounting the photo if you are using corners or hinge tape. You can remove the photo for reframing if you need to easier also, I do this for unframed photos I sell at shows, it gives the customer some flexibility (I put a copyright notice on the photo itself also as well as the mount). Once you position the photo, you can still stick the mat and mount together with double stick tape if you like.
Q3 Why? No, you never want a photo in direct contact with glass or plastic, the emulsion can stick to it and it needs air space.