what do they mean Putty in caulking a timber boat?

[sharkbait]

hi all
i have a 1950's timber yacht, after looking at all views i think i will re-caulk with the traditional method...
the use of caulking cotton sounds like a pain both in the neck and the other end but i understand the principals of keeping the boat tight.
as for next step-they all say methods that use what is termed "putty" and most add linseed to it to keep it soft for longer. nothing else about it.

the last owner used window putty and after 6 months of me owning the yacht the caulking is hard and falling out everywhere
now also taking 20ltrs water in 24hr period. I can understand why they said it was slipped every 12 months... it probably sunk.
i dont want to use polysulfide or pollyurathane and not into debate of it - it all has pros and cons.
what is the best "Putty" to use for the job?
how long should it last?

cheers

[spoinky]

Hi, there are a number of different putties. Window putty is just whiting (powdered chalk) and linseed oil. Traditional boat putty was similar, but with 10-15% white lead powder added (This stopped rot, and it lasted longer under water), sometimes with some grease added.
Some putties used in the 1980's used fine cement instead of the whiting (the oils stopping the cement taking up water and setting hard).
Also currently used is "Duraseal" mixed with fine cement (by hand to a thick putty, I found WD40 gets the crap off the hands after) called "snot" by numerous shipwrights. This stays semi-flexible for a few years, sticks to the wood, and can be scraped off later.
I helped put a lot of this on the 'Alma Doepel' 3 years ago, and it is still good.