Linseed/Lime putty

[jason.p]

Has anyone had experience with using a linseed oil/lime putty for use as a fillet for sealing wooden window frames and stonework. I would like to make it up myself so has anyone done it? Would boiled oil be best as the curing time might be quicker, and what lime (putty or hydraulic).
Thanks in advance

 

[Schoolmarm]

Why do you want to use that instead of linseed oil and burnt sand mastic?

 

[MdB]

Linseed oil + lime sounds a bit of an unusual combination for a mastic. I guess it would be similar to a linseed oil + chalk combination as no moisture would get to the lime to carbonate it. You wouldn't want it to set anyway as the idea is that it is a bit flexible.

 

[Penners]

Linseed oil + lime sounds a bit of an unusual combination for a mastic.

But isn't yer ordinary, everyday putty made of linseed oil and calcium carbonate powder? Not much difference, surely?



signed
Chemistry Ignoramus

 

[biffvernon]

Chalk is calcium carbonate, which is very stable. Hydrated lime is calcium hydroxide, which is less stable as it combines with CO2 to form calcium carbonate. I'm not sure what difference it makes if used for putty. Try it and report back in a year or two.

 

[MdB]

Well I didn't realise that normal window putty is typically made from linseed oil and chalk.

Something new I've learnt today.

 

[jason.p]

I heard of this some time ago from an old builder. Ordinary window putty, I understand is, linseed oil and chalk (calcium carbonate) which is inert with no free lime. The set is down to the oil alone. If mixed with a hydraulic lime "paste", there would be a set due to the carbonation process as well. I can see that lime putty and oil might not work as atmospheric CO2 would not be available for carbonation. What I'm trying to achieve is a thin, strong flexible fillet/filler. Burnt sand mastic is ok for small gaps but not as a filler. What I'd like is something which can do both, and ideally overpainted. The big gaps are being filled with hemp-lime mix (foam or silicone are not permitted on this job!)
Thanks for replies.

 

[skier-hughes]

How big are the gaps? If it's too big for sand mastic, why not lime mortar?

 

[Nigel Watts]

I read somewhere - quite a long time ago - that mixing a bit of gold size into normal linseed oil putty makes it a little more flexible. I did order a tin of the size and try it once but I moved house shortly after and wasn't able to observe how it fared.

 

[jason.p]

Gaps vary as with all stonework. Biggest ones are being packed with hemp-lime. I would normally use lime mortar for the fillet, but would really like something bit more flexible and less prone to cracking so that the fillet can be as small as possible (sometimes if the fillet is too thin it's difficult to control the drying and theres a tendency to crack). I think on the whole the burnt sand mastic is the best option. I could experiment with the lime linseed oil idea but it's too risky, these windows are really high and I'd hate to have to fork out for scaffolding to put it right in a few years :roll:

 

[Penners]

I did order a tin of the size

Large or small?

 

[worms]

Rightly or wrongly, at the weekend I filled some fine cracks between window frame and stonework with linseed putty made into a filler paste with additional linseed oil. Time will tell whether this was a good idea. The cracks were really too narrow to get burnt sand mastic into.

If my chemistry serves me correctly, the need for carbonation to set lime mortar is matched by the need for oxidation to set the linseed oil in traditional linseed putty. So a crack that didn't get any CO2 would probably not be getting any O2 either.