How do you make lime putty?

[JoceAndChris]

From reading the recent thread on this I understand it's OK to use hydrated lime from the builder's merchant. We want to fill a deep channel that we've gouged out in the bedroom for wiring. It's lime plaster there.

Is it just a case of add water until you get a nice goo?

 

[worms]

Joce,

The purists will be along soon to completely confuse us all. But I think you have asked two questions: How to make lime putty? and How best to fill the channel?

Lime putty: Suitable container, pour in some hydrated lime, cover with water give it a stir and wait for a day or three until there is a putty layer at the bottom. Longer it is left the better, it turns to the consistency of cheese.

How to fill the channel? Again the experts will advise and some will say you must use lime putty. But if you are impatient you could probably go with mixing dry hydrated lime and sand then wetting to the right consistency and use straight away. I made a couple of external emergency repairs last autumn this way that I expected to have to re-do this summer but look like they will actually become permanent repairs.

 

[JoceAndChris]

Chris is in a hurry. He wants to do it NOW! (Though it's been gouged for weeks)

Thank you very much, Worms, that's great - glad to hear your repair has held out. Is sharp sand suitable? Or should it be a differnent kind of sand?

 

[worms]

Well, the repair I did was sharp sand and dry hydrate, mixed in a hurry to get the job done before the rain came on on a cold October day. It was one six-inch plant pot of hydrate and three six-inch plant pots of sharp sand (I am not talking about careful measuring here!)

Remember the finish that I needed for an external repair might not be what you will want on your bedroom wall! Perhaps some finer sand would be better, but you are beyond my experience there!

 

[MdB]

Not a purist, but I ditto what Worms has said.

If mixing from putty I would use 3:1 to 2.5:1 sharp sand to putty by volume. When mixing direct from hydrate I would go 2:1 sharp sand to hydrate by volume. Mix well. Very well. It needs to be knocked around a bit. Put any mix left over in a sealed tub and it will keep indefinitely. I would put any left over hydrate into a tub and turn it into putty so that it will keep.

I've not filled channels with lime but my guess is that it will crack along the edges. Not sure what the best way over this would be. I guess I would keep pushing the lime as it drys so as to close the cracks that form and leave the surface 1 or 2mm below the rest of the wall. I would then fill this with 2:1 silver sand to putty at a later date. There is probably a better way.

 

[worms]

I guess making sure that the original material is well wetted might help the new fill to "stick" but given that this is a repair around electical wiring, I think care in the slopping around of water might be required!

 

[JoceAndChris]

You are both extremely kind, thank you so much. That's very clear advice.

This wall will be wallpapered anyway, and once a thousand dresses and shoes are strewn around I highly doubt a touch of unevenness or cracking will be noticed!

 

[JoceAndChris]

Is it just me, or would Penners be making all sort of smut capital out of this thread - I have had to retype several sections to avoid making inappropriate suggestions!

I haven't the slightest idea what you mean! Where's the smiley with the angelic halo around its head?! :wink:

 

[JoceAndChris]

That went reasonably well though He says it's hard to get it smooth.

Here's my filled crack, it still needs a bit more filling though!:

PS. I did NOT put the pic rail in, but it's staying.

 

[Penners]

Is it just me, or would Penners be making all sort of smut capital out of this thread - I have had to retype several sections to avoid making inappropriate suggestions!

You needn't think that your totally unfounded slur can be made with impunity, just because you're hiding near the edge of the world and writing in 4pt type.

I have eyes everywhere...

 

[MdB]

That went reasonably well though He says it's hard to get it smooth.

Lime mortar isn't a fine filler, it is full of sand so it is as hard to get flat as cement mortar would be.

I've not tried what you are doing but if it were me, I would remove any overspill of sand either side of the joint and then use Polyfiller so get a smooth finish. (Polyfiller is plaster of paris + cellulose and is breathable if I remember correctly). As before, there may be a better way of doing this. Lime experts please comment.

 

[fjpdesigns]

For a really fine finish you could try a lime putty/powdered chalk mix. I have never tried it myself. I have, however, seen it used. It's very sticky and needs hair in it. It can be obtained from Anglia Lime (01787 313944) near Sudbury in Suffolk. £14.40 + VAT for 15 litres. They also sell fine chalk seperately at £3.10 per 25 kilo. Obviosly p&p will have to be added.
You can also get the chalk and putty from Hendry and Son Ltd in Dereham, Norfolk (01362 683249).
There may be somewhere closer to you.
Hope this is of some use.

 

[JoceAndChris]

It is useful, and really good to know about it, but as so often with these things 15 litres seems like overkill -if I had loads else to do I might consider it.

I didn't know Polyfiller was breathable, I've been racked with guilt every time I've used it!

 

[worms]

It is useful, and really good to know about it, but as so often with these things 15 litres seems like overkill -if I had loads else to do I might consider it.

If you bought a 25 kilo bag of lime for that repair, then chances are you still have about 24.5 kilos left over, so don't go buying any lime putty!

If I was botching this job myself, I think i might have tried wetting the mortar a bit to bring some of the lime to the surface and if that didn't produce a smooth enough finish, a couple of coats of lime-wash ever the top might help fill in any remaining roughness from the sand.

just because you're hiding near the edge of the world and writing in 4pt type

...and removed the offending comment, lest it offend! But not quickly enough it would seem!