I have softwood single glazed window frames ( about 25 years old ) in a very punishing south facing elevation and the putty shrinks and cracks a lot, on the bottom bead particularly, and needs replacing. I would be grateful for any thoughts as to whether linseed oil putty is the best replacement like for like or are there good alternatives that will adhere to softwood. If not would it help adhesion to brush a little linseed oil into the cleaned rebate before putting in the new putty? Thanks, jim