If you think it
is linseed oil
, but looks too shiny, like a varnish, then maybe someone put it on with a trowel.
In which case...
No need to cook the stock - and maybe warp it.
Just take a roll of paper kitchen towelling and some natural turpentine. Moisten a piece of paper towelling with the turpentine and rub down the stock. Quite possibly, it will take off a lot of gunk. And dull the shine. Keep at it until the wood has a "normal" appearance for an oiled stock, and polish off any traces of turpentine. Adequate ventilation is advised, so that you don't get too happy on turpentine fumes! If natural turpentine has
no effect whatsoever, then the finish is
not linseed oil
!