It's a combination of what others have already said...the iron is 'melting' the finish/starch/sizing (not melting the fabric) on the high spots and the solution is a pressing cloth...which can be any washed piece of fabric. Dampen one of your spots and see if it's gone when it dries.
ETA: Hammering high spots is not healthy for fabrics or anything made from them. Instead, press your seams so they lie flatter and don't bunch up. You'll get that shine on any spot that's higher than one layer of fabric, so hammering won't solve the problem anyway. Why break threads trying?
Last edited by ghostrider; 07-20-2012 at 09:01 AM.