Roger Bisby mixes it up with some Smig Plaster and fills us in on the results.
A few months ago I went out on site to see a demonstration of a polymer spray finish plaster.
The product in question was really the kind of thing you buy by the pallet load because the polythene sacks full of ready-mix just wouldn’t survive being thrown into the back of a van.
This time I have been out to look at a similar, but not identical, ready-mix plaster which is packed in plastic tubs specifically to survive the journey from merchant pick up to site.
Also the tub allows you to dip in over the course of several months so it is an ideal product for decorators, plumbers and electricians looking for a convenient plaster to do the odd bit of making good.
That said, I don’t want to give the impression that this is not a serious product for the professional plasterer or dry liner. It is used in the ready-mix form by plasterers all over Europe.
In essence this gypsum, polymer plaster is joint filler, and you can use it for that very purpose with a paper tape, but it is also intended to be used to plaster walls and ceilings.
It has more flexibility than unmodified gypsum and it resists cracking and shelling so it is ideal for difficult surfaces. There is no need to use a PVA because the adhesion is phenomenal.
In the right hands it gives a smooth white finish onto board and all kinds of backing.
I added the caveat ‘in the right hands’ because it took me a little while to get the hang of it. Unlike Thistle gypsum it does not set rapidly.
The air-drying takes time and although you can build it up to 6mm, at that thickness it could be a matter of hours before you can trowel it up.
My mistake was that the surface wasn’t particularly flat so I was trying to build up areas of different thicknesses. What I should have done is to use it as a base coat to flatten the surface and then come back the next day to give it a skim coat.
I have no doubt that I will improve with this product and for the jobbing builder who does the odd bit of plastering as part of a refurbishment or extension Smig has some real benefits.
I would be very interested to see it being used by someone who knows the product well. I noticed when I collected it from the merchants that it is also sold as powder in bags so you can mix it up as you would any conventional plaster.
I decided to give this a go and I am happy to report that I fared a lot better with the powder. For a start I could mix it to the stiffness that I preferred which meant I could trowel it on with a bit more control.
I mentioned that it is basically a variation on joint filler and, like joint filler, you can sand it. That means that you are never going to produce a bad job because you can remove the high spots and apply another coat to fill in the voids.
The ideal way to do it is with a giraffe sander with dust extraction. It is a different approach but it is very effective. Will it catch on in a significant way in the U.K?
To be honest I think that plasterers brought up on conventional gypsum based plasters are going to be hard to convert but it opens the trade up to decorators, dry-liners and jobbing builders who can’t hang around waiting for the plasterer to fit them in and they might also think that pocketing the money rather than paying a subbie is the way to keep a little more value in the job.
The fact that it is white also means that the job looks a little nearer completion. I am not sure about decorating. Being a polymer I don’t think a mist coat has any advantage but I will try both ways and report back.