Painting over putty.

[Perthite]

When renovating old sash windows and putting putty on the outside is all cool except that the polyurethane paint lifts from the puttied areas over time.

I assume that this is due to the putty not being dry and still having linseed oil so the paint lifts, never bonds to the putty. Should I wait till the putty dries before i paint? If so how long? Or maybe there is a "trick" someone can pass on .

Thanks in frustration

[jmk89]

Because of the oil in putty, I always use an oil-based paint. This seems to work for me!

[baxter]

I have always been of the understanding that you should allow putty to set/dry for around three months before applying any painted finish. After that time I don't think that the type of paint matters.

But how many have noticed the warning on the cans of water based paints that the paint should not be used on windows because they can stick and not slide up and down.

Know of a chap who learnt the hard way, hurt his back straining to open a stuck window.

[echnidna]

is the poly exterior grade?

[durwood]

normal glazing putty is a mixture of mainly linseed oil and whiting powder plus other ingredients.

Its meant to stay firm and not rock hard for years so it can flex and move with the timber therefore keeping a seal and adhesion.

Eventually it does dry out but depending on the climate exposure to sunlight and heat it could be years.

The answer is as jmx89 says use oil based enamel it's from the same family. the linseed oil is thinned with turps as is the paint and the oil is a linseed oil or synthetic oil so the paint has no problem sticking.

All other paints are being painted onto a oily surface so no or little adhesion for them.

The putty should be treated the same as wood pink primer/undercoat and the enamel colour for best results. Normally the putty only requires a few days to set before painting, if you buy premixed putty the manufacturer will advice on proceedure. If you mix it yourself make sure you have the correct information as to how to mix it, not something most people would do at this time.