Putty and paint advice for sash windows

[scholar]

I meant to add that I have found the technical advice line at F&B to be very helpful.

Cheers

 

[markturner]

Thanks - though the F&B guidance says use acrylic putty then goes on to advise assuming thats whats used, does not mention trad putty:
"If replacement putty is required for new or existing glazing, for best results use an acrylic based glazing putty which is designed to work well with modern water based paints and primers. Bare wood must first be primed with an undiluted coat of Farrow & Ball Wood Primer & Undercoat, including the end grain, and allowed to dry for a minimum of 4 hours drying times before applying your chosen Farrow & Ball finish as follows: Exterior Eggshell and Full Gloss - Apply an undiluted coat of Farrow & Ball Wood Primer & Undercoat in the correct colour tone for your top coat (allowing a minimum of 4 hours drying time between coats) followed by 2 coats of your chosen top coat (once again allowing a minimum of 4 hours drying time between coats). Ensure the glass is thoroughly clean and overlap the final top coat onto the glass by approximately 1mm to achieve a seal."

I will contact F&B tomorrow though, as it does seem that I should be using an oil based primer on the trad putty....makes sense to me as well.....

 

[markturner]

OK< well, F&B technical dept told me that in this case, teh primer I am using ( Tikurilla Otex) is great, however their water based products should not be used over the top , especially in conjunction with linseed putty, for several months, to fully allow all the solvents to offgas......this is whats causing the hairline cracks.........so now we know! I will primer the windows and fit and drop them out to paint the putty late spring / early summer

 

[Jacob]

OK< well, F&B technical dept told me that in this case, teh primer I am using ( Tikurilla Otex) is great, however their water based products should not be used over the top , especially in conjunction with linseed putty, for several months, to fully allow all the solvents to offgas......this is whats causing the hairline cracks.........so now we know! I will primer the windows and fit and drop them out to paint the putty late spring / early summer

I wouldn't use F&B in the first place. It's a more of a marketing operation than anything.
Linseed oil putty does not "off gas" there are no solvents involved. The oil does not evaporate it oxides. Hence must be painted with something oily (to stick to the oily surface) and breathable i.e. not too dense an impenetrable film, to allow oxidation to continue.