phil.p":1esswqbd said:
"You'll have to do it all over again in a few years ..." - no more so than with putty, and probably less. I can think of scores of occasions I've picked out loose putty and replaced it - but never a two part.
I've struggled to pick out 100 year old putty.
It doesn't work on it's own: window rebates need shellac (which would be good for the OPs nail prob and very quick to dab on and to dry) and putty needs linseed oil paint ideally. It's less good under modern paint (as is anything/everything).
I've been fiddling with old joinery for most of my life and actually know what I'm talking about. I've come to the conclusion that the whole plastic window industry has come into existence not because of failed timber but because of failing modern paint. Once the old paint has been stripped from an old item of joinery its life has been drastically reduced unless it is re-painted with linseed oil paint, but it's the timber wot gets the blame.