Recently bought a vintage silk fly line of eBay. It is spotlessly clean and very supple. At a guess I would say it’s lost any resins it was treated with. H ow do you think I should treat this line to see if I can restore it to a fishable condition.
Silk fly lines are 'treated' after construction by thin applications of a mixture of boiled linseed and varnish. If the line you've purchased isn't 'tacky' but is spotlessly clean and supple then treating it with a number of light coats of Red Mucillin and leaving it, between coats, in loose coils, in a shoe box should be all that's needed.