I just finished refurbishing some stag handles on a knife, and I thought I'd pass this tip along.
I have a knife that has stag handles and the stag was really dried out - to the point which I feared it might crack. I use (clear) mineral oil on my stag handles. It won't turn rancid or harm the stag (at least, it has never harmed mine). It seems to work very well in refurbishing old, dry stag. I apply the mineral oil with a Q-tip. You can buy it at the drugstore.
(I have also heard of people using lanolin wax, but have never tried it).
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