I have tanned about 10-12 hides now and I am noticing a pattern: the hides that have been air or "trapper" dried will not swell in the pickle. The skin is hard, dark, greasy, and "crispy." If I attempt to shave them with my fleshing machine, it just puts holes in the hide. The most recent one I put in today won't even rehydrate. Its just a hard folded hide sitting in the pickle. I could probably pull it out and wipe it off with a towel. I have not had this problem with salt dried or frozen hides. Does anyone have any idea how I can fix this or why this is happening? I use Pro-1's Pro-maxx tan.