Linseed oil is just a wood finish, like tung oil. I mention it because it's particularly good at reviving distressed wood -which will be the inside of the grip, when you burn it in.

You normally apply it just like any wood finish -rub, rub, rub. But in this case, it might be good to soak the piece in it -or failing that, soak a rag and stuff it into the tang hole.

Heating to red is fine, IF you still need to heat-treat the knife. But if you do, the tang might change shape somewhere along the process (especially if you haven't done your final grind!) and that too would defeat the point of burning the tang.

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