OO Soaps are tricky, especially if you use a water discount; there is a fairly narrow window where the consistency of the soap is good to stamp easily before it gets so incredibly HARD that you will need metal stamps instead of acrylic or hard rubber.
I find that my OO soaps are good to stamp on the third day right after I unmold. I use 1.5:1 ratio on my water:lye, so YMMV. If I wait until day 4 to unmold and cut, the soap is already very hard and getting harder every day.
The texture I look for is like unto a very firm chees (say, a parmesan or smoked sharp provolone, or aged swiss). At that point, I cut, smooth and stamp. Also, I d not mallet my stamps. I press them firmly by hand after dressing them with glycerine or mineral oil. I may or may not also dip them lightly in mica. Both activities, I find, help the stamp to release. Then I clean the stamp thoroughly between bars with a cotton swab when I dress it again with mineral oil.
