Ceiling plaster recap

[piper]

Well, at last I am about to try lime plastering the ceiling of the bedroom I first posted about over a year ago.
I've collected a lot of information, and read a lot of advice on this forum and elsewhere, so just to recap one or two things that have sunk almost without trace on previous threads. Please bear with me.
In the end I have got sawn larch laths from Ty Mawr. I know that cleft oak, sawn oak, or cleft softwood are theoretically better, reedboard has also been recommended, but I want to try and do it almost as it was, with lath. The old laths seem to have been softwood, though mainly look cleft(probably Victorian or later), and anyway, the cost of oak is prohibitative. I even tried a local coppice worker, in the interest of saving lath-miles (!), still too expensive, and not surprisingly he didn't seem too keen. After all this time I could probably have cleft them all myself, or sawn them - but in the end life is too short.
Questions; (as I said, bear with me. These have mostly been answered before, but I'd like confirmation)
1. Nails. If possible I propose to get galvanised 1" (or 3/4"?) from local ironmonger. May even dip them in linseed oil. OK?
2. I have my tub of well matured lime putty in the garage, home-made from dry hydrate back in the Summer. Does the sand need to be washed?(3:1 mix coarsish sharp sand for the first coat - right?)
3. Hair. I have bundles of horsehair from Ty Mawr. (Incidentally, it appears to be Chinese. What price eco- awareness now? What about hair-miles??) I believe it should be cut into about 2 inch lengths. Is that right?
4. Apply first coat to about 9mm thick, pushing firmly to get good key, get severe aching shoulder, plaster in the eyes etc. After it begins to dry score the surface thoroughly, smooth out cracks etc. Is the full three-coat process really necessary, or can I get away with going straight to a finish coat of 1:1 putty and silver sand, unhaired? On second thoughts this may be too thin, so what mix should the second coat be?
I may well end up getting a professional plasterer at least to do the finish coat, but would like at least to try it myself first.
(later edit to post) I forgot to say I know that the laths should be well wetted.
Thanks for all the education, folks.

 

[Gervase]

You've pretty well got it covered. Nothing wrong with sawn larch - I use them all the time unless the client specifies and is prepared to pay for riven oak. One inch glavanised clouts are fine for fixing; put them in a large tin with some linseed oil and give it a good shake and then tip them out onto newspaper and you'll be fine. Don't worry about washing the sand.
As for hair, one and a half to two inches is fine - one two-inch bundle teased into each mixer load should see you OK.
If your first coat is nice and level (a plasterer's feather-edge is handy for getting that right), then you can lightly score with a scratch comb the next day and get away with just two-coat work with the second, unhaired, coat made from two-and-a-half to one sharp sand and putty - wet the surface well and float on the second coat to about 4mm thick and work it well with a wooden float as it sets and contracts, and then use a mist spray or a wet wallpapering brush in one hand and a steel trowel in the other to get a fine finish.
You'll probably need to make the mix a bit wetter than you think to allow it to push up between the laths and make good nibs, and doubtless you'll find the first coat frustrating at first, but remember always to push the trowel-load of plaster towards the stuff that's already stuck there and to keep a good pressure on the trailing edge. Use a hawk and, if you're deft, you can catch any dollops that drop off. It's a knack that's not hard to master, and you'll be hugely satisfied when it comes right.
Good luck!

 

[Penners]

I have my tub of well matured lime putty in the garage.

I wouldn't presume to try and embroider Gervase's expert advice. But just one thought about your comment above: there's no risk of the lime putty getting frosted in the garage, is there?

 

[biffvernon]

We had a discussion about frost danger to tubs of putty about three years ago. I've been keeping a tub especially to test but the last couple of winters have been so mild there's hardly been a skim of ice on the surface.

The thing is, I can't really see why it should do any harm if the putty did get frozen solid. Why would it be any different on thawing? It's not like stawberries.

 

[Gervase]

I've had some 25k and one tonne bags of putty which have been subjected to a pretty hard frost and haven't noticed any adverse effect. All my lime is stored out of doors winter and summer, and - so far - no problems.

 

[piper]

Gervase, Thank you very much indeed for that helpful and encouraging reply. I rather hoped it would be you that sent me my reply I'll start nailing up the laths very soon, and the job may be finished by (next) Christmas!
I posted a question about lime putty freezing only a short time ago, and the consensus then was that I needn't worry about it. Not that it's freezing yet by any means, even up here in the so-called cold North.

Incidentally Gervase, this is off-topic, but while searching for previous posts from you about plastering, and while on the subject of warm winters, I found this in the incredibly long recent thread about climate change.

I used to work with Christopher Monckton. I'm sorry to have to tell you that's he's barking mad

I was at college with him, and I entirely agree with you. "Barking" comes nowhere near expressing the degree of madness.

 

[biffvernon]

Some notes on the Barking Viscount

 

[Penners]

I've had some 25k and one tonne bags of putty which have been subjected to a pretty hard frost and haven't noticed any adverse effect. All my lime is stored out of doors winter and summer, and - so far - no problems.

Apologies if I was being alarmist. Being ignorant in such matters myself I felt that the question was worth asking.

 

[Gervase]

Oddly, everything I've read says to keep lime putty away from frost, but experience would appear to indicate that it's not a problem. Admittedly a solid frozen chunk would be a b*gger to mix...

 

[Penners]

You could try peeing on it. Lime and uric acid could be an interesting reaction...