A tanned hide that is intended for a rug with a half head mount will need to be softened before it can be finished. The face, ears and head will be inflexible to the point that the ears cannot have liners put in and the eye holes will not seat around the glass eyes. The face will not stretch over the head form until the hide is relaxed. A tanned fur pelt or hide that has grown stiff with age can be softened by the same process. The ingredients for softening can be purchased at a grocery store.
Pour 3 gallons of cool clean water in a bucket. Add 3/4 cup of borax and 1 tsp of dishwashing detergent to the water and stir it thoroughly with a wooden stick.
Put on rubber gloves and place the hide in the solution and move it around with your hands so the water reaches all areas of the hide. Leave the hide in the solution for two hours.
Remove the hide from the solution and squeeze all the excess water out of it. Roll the hide up with the head and the feet (if there are any on the hide) inside the roll and leave it rolled up for four hours.
Check the hide after four hours. Pull on the face and ears to determine if they are soft enough for mounting and the body stretchable. If the hide is still stiff with little stretch to it, roll it up again and check it every hour until the hide is soft and the head completely malleable.
Unroll the softened hide. Proceed with the head mounting or stretch and tack the hide out flat on a sheet of plywood for drying.