how to plaster a wall (first coat)

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start with a bare wall, loose material removed, brushed down and lightly wetted .

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apply plaster around the edge like a frame ; i got the left hand one flat then some horizontal ribs to project the levels to the other side, then complete the right screed

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fill in the blank areas bring level with the frame. This is only the first coat but it is brought level, if it isn’t what is the point? After trowelling I went over it with a couple of straight edges; one long, one short – up and down and side to side sawing movement across the surface just to take off the high spots.

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key with a comb ready for the next coat, which will be easy as this is already more or less level, some shrinkage will cause this first coat to be less level than it was at the start, this wont crack because there is enough hair in it to stop that but it will still shrink.

So there you have it, a very small bit of wall I know but the principles are the same all the time, get the plaster level with the first coat not the second, the second coat just brings the plaster to the correct depth. If your first coat is not level what was it’s purpose?

 

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my Japanese plastering trowels

my-plastering-trowels

These are the only plastering trowels I use.  Starting at 9 on the clock: a medium sized Jigane laying on trowel,  next a little really flexible polishing trowel, at the top a larger jigane, recently used for laying on the finishing plaster, at 3 a medium sized Honyaki finishing trowel which I also use for the finishing plaster. at the bottom a smaller Honyaki which I use both for laying on and compacting the finishing plaster, then at 8 on the clock, my new Honyaki trowel solely for compacting and smoothing. Also three small corner trowels.

 

 

 

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Renovating old domestic plaster surfaces

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applying the first coat of finishing plaster

A testing job for my own recipe JBLime finishing plaster but one that any other lime plaster may well have not managed so easily.

The walls are generally old lime plaster but have been painted with emulsion, wall papered and patched and in places over skimmed with nice pink gypsum. The main patches were done with limelite.

In the picture you can see the new finishing plaster going on (the darker grey)  Areas where limelite was removed and replaced with a new lime plaster and the green is the wall prepared with a grit primer after the wall paper was removed.

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The fire place was a bit of fun. The three walls are gypsum apart from the one on the left which is half plastered in cement. They were all painted with emulsion which was easily scrape off. I keyed the gypsum to get a good mechanical fix for the plaster skim.

The wall can be seen with the grip primer, I did not want to entirely rely on the grip coat so I also keyed the old plaster with my spiked roller (lime plastering plasterboard. with the correct tool and material it works well.)  which has come into its own for breaking through the surface of painted plaster. It takes a fair bit of force but it soon does the job and gives a decent key without making a great lot of damage, it is also useful for stressing the plaster all over so that any loose or suspect bits of plaster are soon found out and can be replaced.

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The final coat applied, all smoothed and flattened. It is still drying here and there; on a job like this, with all the different substrates to contend with, drying is very uneven. The new lime patches at the bottom reached trowelling condition within a couple of hours, the plaster on the cement took two days. The plaster on the gypsum was reasonably quick being trowelled the following day, which just called for patience because as I said, the left hand side was gypsum down to half height then cement, which, to add a little extra difficulty, was set back from the gypsum half about 3mm so it needed and extra coat of plaster. The rest of the grit primed plaster reached trowelling condition about 24 hrs after application.

When I say trowelling I mean flattening, smoothing and compacting.  The window of opportunity for trowelling is quite wide, although there is a sweet point when it is perfect. If you try too early the plaster can form the occasional little bubble and it is very difficult to remove the trowel marks, trowelling too soon is best avoided but there are times when you need to do it, this is when I know that if I leave the trowelling overnight it will go too far and be almost too dry for the trowelling to be easy the following morning, in that situation I can carefully trowel the plaster smooth and then in the morning all I need do is go over again for the final compacting and smoothing.

Of course all this is so much easier when the plaster is flat, undulating plaster is such a chore and for that I find I have to use the really flexible, venetian plastering type trowel, but for all other plastering the trowels I use are rigid, that appears to be the Japanese tradition, rigid trowels for laying on, with practice you can get the plaster pretty flat without the need for floating, and even on this job, which was mainly skimming I used a very rigid Japanese Jigane trowel.  ( http://japaneseplastering.blogspot.co.uk/p/blog-page_10.html)

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Honyaki finishing trowel – the blade is quite rigid with only the slightest amount of flexing under pressure. It compacts and flattens to achieve a very hard wearing lime plaster surface.

 

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Tricks of the trade 2

What is my most important piece of kit?

The fantastic Japanese trowels I use?

My handmade wooden hawk?

My paddle mixer?

no none of them. The most important piece of kit is my plasterers light because without harsh side lighting it is near damn impossible to get a consistent finish – no matter how good all the other kit is.

 

Image result for plasterers light

this is mine but there are others and possibly better ones.  Get one if you haven’t already.

 

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Recipe for course stuff

My recipe for course stuff:

3 parts lime putty

1 part horse hair about 30mm long

6 parts sharp sand

method:

put the lime putty in a mixing tub such as a large trug, add the hair and stir it in so that the hair disperses. add half the sand mix with a plaster whisk then add the rest of the sand and mix again.

Some hair will get tangled on the whisk this needs to be taken off before it is used again.

I use a propellor whisk from Refina

MR8 120G Impellor Paddle this grabs less hair than a basket whisk.

 

 

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update on silly ideas 1

On reflection it really was a silly idea in that it did work but was totally not needed. And this is the point. Despite the mix being 1 lime to 2 sand and the plaster being on average 20mm thick and in places a little more, I got no cracking and the reason for this is simply the quantity of hair.

 

 

 

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Silly ideas that might work. no.1

I found one of these in my local store, I think it’s for rubbing horses down. The balls rotate as you move it around.

The idea:

now that my plaster is drying nicely ready for the top coat, but despite the quantity of (horse) hair I have put in it and due to the quantity of lime putty I have put in it, there is a little bit of cracking  – no much – just a teeny bit. But because I don’t want to smooth off the surface too much but do want to close up the small cracks I thought this would be worth a try.

they are only £4. The balls press against the plaster as you move it around the wall pressing in the plaster but leaving a nice compacted groove behind, it doesn’t gouge out the surface but it does compact without smoothing.

Of course, this doesn’t replace a float in that it won’t smooth off any lumps and bumps but it does compact as I say and for  four quid what’s to quibble about.

It comes as a mitt type thing but I couldn’t get my hand in it very easily so I am going to cut the back off and fix it to a plastic float, I might get two and fix both to the same float. they will fit ok so why not.

I have tried it out and it seemed pretty effective, but the thing is not to use it on soft plaster as it does gouge, the surface needs to be quite firm but still slightly pliable, which is about the time the cracking has stopped.

I must emphasise that there isn’t much of this cracking and it’s only due to shrinkage caused by the mix being 1 part lime putty to two parts sharp sand.  or to be more helpful: 3 parts putty, 6 parts sand, 1 part horse hair.

It’s funny how cracking has become such a bad word in plastering, look at any historic plaster and there are cracks all over, some are subsequent to it being plastered and probably down to movement in the building but some, and they are easy to spot when you know how, are cracks that were caused as the plaster dried and shrank. As long as the plaster has not actually pulled away from the wall as it can do with excess shrinkage, a little crack here and there is not a problem to worry overly about. Close up the cracks one way or another then when it has dried enough so no more cracking is likely, on with the JBLIME FINISHING PLASTER  and the jobs a goodun.

 

 

 

 

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