Advice needed on repointing.

[Nemesis]

Slaking lime is often done, in tiny quantities, to demonstrate how, at SPAB lime days. Makes heat and fizzes.

Goggles and gloves, and no-one has died yet.

 

[MdB]

AFAIK, NT is correct in saying that there is no difference between lime mortar made from putty and lime mortar made from hydrate. There certainly isn't any difference chemically. I've not been using it enough really to comment but others here have and nobody apart from the manufacturers of the putty say that there is any difference. I've gone down the bagged hydrate route myself and I don't bother with hessian for my pointing. I just keep it damp for a few days. If it all falls of in a few years, then I will just have to do it again. I'm certainly doing a better job than the cement ribbon pointing which was put on a few years back and is now (fortunately) all falling off.

 

[charlie-ia]

tried mixing the lime with lots of water as suggested, and youre right, much less dust, and so much less effort.
however, when we mix the putty with the sand the result seems much too wet. what have we done wrong? the sand seems the same (new bag, but doesnt seem any different) and we let the putty drain a bit before using it.

before, we mixed the putty (admittadly VERY stiff) with sand and worked it untill it looked like on the lime course we went on. now we dont have to mix it so much to get the mortar blended properly, and after a few minutes a small amount of standing water appears in the mortar bucket.
im baffled cos this time we left the putty to sour for a month, so i assume its all settled properly, much longer than we have been able to leave it before. could not mixing the water and the lime properly initially be the problem?

and whats the best thing to add when it is too wet? more lime powder, or more sand? or a bit of both? or just start again- we havent made a vast quantity. the first mix we made last week has started to show signs of cracking (though it was windy and the cover kept blowing away)

 

[MdB]

How long did you let the putty stand before using it?
Did you drain all the liquid from the top before using it? I sponge the top to get the last of the really wet stuff off.
Was the sand very wet when you used it?
How well did you measure out the 3:1 ratio? 2:1 will be a lot less stiff than 3:1.
In my limited experience you only need a very small amount of water to turn the completely change the consistancy and too wet does crack easily.

The good news is that if you have mixed a batch too wet, then simply shove it in a sealed tub and leave it for a week or two. When you open it up, there will be a layer of water on the top which you can then drain off.

 

[charlie-ia]

ah, no, i just let it drip a bit, did wonder. the rest of the putty is still in the bucket. and the measuring was a bit iffy, though last time it didnt seem to make much difference (though the putty was fresh then, this time it has had almost exactly a month)
the sand wasnt wet, just nice for making sandcastles!

do you use the water off the top again to make more putty or does this lead to contamination? we are no where near needing limewash

 

[MdB]

do you use the water off the top again to make more putty or does this lead to contamination? we are no where near needing limewash

I just chuck it on the garden....

 

[charlie-ia]

im doing something right then!

 

[NT]

Adding a bit of dry material is a perfectly good solution too, and much quicker than leaving it all sit for ages.


NT

 

[piper]

I understand from the other comments that the only advantage of making putty from builders merchant hydrate rather than using the hydrate powder directly is that it doesn’t blow around and it keeps better.

I have limited experience, but when I have made up a mix using dry hydrate and sand BEFORE adding water, I have had the d*'s own job to get it mixed evenly without innumerable little hard lumps of lime, in fact I didn't have the patience to keep mixing, because the only way was to pick up each little lump and crush it individually between finger & thumb - Blow that for the proverbial game of soldiers. Maybe it was because the bagged lime had begun to go off? Consequently, the finished render has a rather attractive white-speckled finish , but it doesn't matter because it's near floor level in a utility room, behind the sink. Other bits are in a garden wall.
Subsequently, I have mixed it to putty first - much more successful, but with the problem of the mix being a bit too wet. Still, it's all a "learning curve".
Now for my question - most of the home-made putty is still under a layer of water in a plastic dustbin in the garage, and it's now about four months since I made it. Presumably it will keep virtually indefinitely as long as the water layer is in place, though perhaps I should try to use it before the really cold nights start?

 

[Nemesis]

Excuse haste - too much to do too little time... it will keep. For a long time. Try not to let it freeze, but my experience of problems with freezing relate to when putty used to point and there is frost.

 

[charlie-ia]

i read somewhere that when a roman architect had a newborn son he made a big batch of putty in a sealed pit and kept it until the son was a man and gave him it as a wedding present. dont know how true that is but it does imply it will keep a while. (cant remember where i read it, apologies if its off another page here)

 

[Lady_Mari]

charlie-ia, did the article say what the son then did with his pit 'o' putty? (maybe the new missus had to do a bit 'o'puddlin').
Spose the tradition died out from a shortage of sealed pits.

 

[worms]

I'm afraid my experience of this is at odds with Piper above. The dry mix has been much easier to make than trying to get putty and sand to mix evenly.
I suppose it is like baking - any fool can mix the dry ingredients together, flour, sugar etc but I never did master the art of crumbing butter into flour!

We have discussed the effects of winter on the putty bucket before. I've had no problem with this in a bucket stored outside, but we haven't had a decently hard winter in the last couple of years to really test it. (Unless of course, my failure to get it to mix is related to the cold-storage!)

 

[ian]

do you use the water off the top again to make more putty or does this lead to contamination? we are no where near needing limewash

There is a school of thought that the clear liquid from the top of settled lime and limewash buckets is valuble resource. I think is in the Ashurst conservation series about using this lime rich water to stabilise an old friable lime plastered wall by repeated spraying with this. Needed gallons though so it's more a dedicated conservation technique. Seems to me you might as well hedge your bets and use it in the sprayer for the "aftercare" damping.

As for frosted buckets of lime, I had no trouble knocking up and using lime mixes from buckets that have got frozen over winter and thawed indoors before using. As long as the curing is without frost and at resonable temperature and not allowed to dry too quickly. Maybe I'm just lucky

 

[Gervase]

I save the water to use for wetting down before plastering as it does act like a 'tack coat' to help plaster adhesion. Any old bits of putty left in the tub get shwooshed around with water and added, so what you end up with is a very dilute limewash, which is ideal.

 

[Jon Maine]

I have a friend who is an archaelogist who lifted a flagstone down in the vaults of Wells Cathedral to find 900 year old lime mortar which was fresh and uncarbonated.

No air, moist conditions no set.

Just an interesting snipet.

I would out of preference use hydraulic lime for pointing. If no time or finnancial constraints were present I would consider lime putty.

I would not use hydrated.