im a pretty practical bloke, i can turn my hand to most things. so im trying to master plastering as ive no money but have time on my hands! (im renovating my house).
i started yesterday after purchasing a 'ragni' plastering trowel from b&q. i also got a whisk and bucket. i had no trouble mixing the plaster (thistle multi finish , b&q) and got it to the correct constituency. it went on pretty easy, or so i thought! this morning its dry, and theres of little ridges and little depressions in the surface. i thought i had smoothed it off correctly but it seems not.
q) how can i remedy this? a layer of pva (dialuted 5:1) plus a further skim?
q) how do i avoid this? what am i doing wrong? or is it just down to learning how to use my trowel correctly? does the trowel need a sharper edge on it? if so.. square? or beveled?
hope someone can help.... thanks in anticipation .
Not with the immediate problem but what you would have found a help is a "Plasterers Derby".
The Wickes one is a tenner and is a four foot length of aluminium with handles on. You use it to go over walls to finish plaster off. It is fairly easy to use.
I spent months (or it seemed like months) plastering a 6 x 3ft section of wall. I eventually got it relatively smooth, but not a patch on what a pro plasterer could have done in 5 mins for about £40.
I hate to sound defeatist ('cause I'll give most stuff a bash!) but plastering really is a black art and can drive relatively sane people to the brink. If you really do have excessive time on your hands I would practice on a 'spare' bit of wall first - plaster it, polish it, scrape it off before it sets, repeat 5-10 times. But honestly, don't despair if it still looks crap. Pro plasterers have in-built spirit levels and gyros to keep everything flat, IMHO. :-)
Unless it's just bits of patching I always pay a plasterer now.
You can do that if you like, sure beats the hell out of sanding it all down.
The ridges are there because you trowelled it up too soon, IE the plaster hadn't set enough...plastering, like anything else is easy if you follow a tried and tested method: Get the wall ready first, don't start mixing until you have done this...PVA over everything, except plasterboard, you can apply the skimming while this is wet or dry....if the wal is p-board, get it scrimmed up all along the joints and make sure no nail/screw heads are proud
1) mix
2) get a coat of plaster on the entire wall, don't bother about any marks, lines or anything else, just make sure the entire surface is covered fairly evenly (even as in the same thickness - don't have it a mm in one part and half an inch thick elsewhere, unless this is unavoidable.)
3) have a brew, wash your trowel, bucket etc and clean the mixing bucket
4) 10 mins later, do another mix, half the size as the first mix.
5) apply this t-h-i-n-l-y over the now partially set first coat, you are only really using the new mix to fill any hollows and you will see that it is much smoother already than the first coat.
6) wait 10 more mins when you've finished the 2nd coat, then with a clean trowel and clean water, splash a small amount of water on the upper left section of wall and work your way L-R, then the same at the bottom. (the handle side of the trowel should be kept clean at all times, if any bits of plaster are visible when looking down at the blade, clean them off, have a wet brush and bucket at all times when plastering).
7) repeat number 6
Some people attempt to do large walls in one coat, but it's false economy, firstly, it saves them 75p worth of plaster, but they spend longer trying to get a decent finish on it, and secondly, because they think they are saving time by 'not doing it twice', instead they end up going over it a dozen times trying to get it right, whereas with the method mentioned above, it gets two coats, laid down once and finally polished, but there's less effort goes into those 'four times over' than 'one coat and struggle for hours'...the end result is a smooth finish suitable for painting, if the walls are to be wallpapered and it's your own house, you can leave the final polishing, but for the sake of an extra 30 mins easy work per wall, it's not worth leaving.
Congrats on the Ragini BTW, excellent trowels...you can rub the sharp corners off on a brick if they are giving you too much grief, just make sure there are no 'burrs' on the face of the trowel side...they only need half a dozen scrapes on each corner, just to take the sharpness out.
Yes, providing the wall is flat to within a couple of mm (or less if you're a novice).
Yes. Search this newsgroup on google. I and others have posted how to plaster many times. Also check instructions for breaking in a new trowel, which is not initially easy to use.
No, it's for leveling the scratch (under) coat, not polishing the finish coat. However, a straight edged piece of timber is at least as good, and possibly better IME.
That's what I found with the derby. One rounded edge and one sharpish. Worked like magic on the setting plaster, following advice given elsewhere in here. :))
Of course, this, in my experience is the hard part. Polishing and stuff is easy, but if you can't judge flatness at this stage (or on any second coat - but I've never seen a pro doing plasterboard skim in 2 coats), the later stages will not correct it. You can only shove the plaster around later to correct a certain amount of wobbliness. You can remove localised dips, scrapes etc later, but if the initial flatness is not close enough, you have a problem. And this is where I got stuck.
Again, I find its the large scale lack of flatness that is the problem. If a hollow is smaller than the trowel, no problem. Any it's easy to push too much plaster away so that you create undulations in the direction of the trowel. You can to be able to "feel" flatness under your trowel. And I have found no magic trick to help with this.
I did an area of wall above a door and I used a thin batten to do the initial application, then polished if off and it looked very good. Because the inital flatness had been there. One thing about 2 coats, if you apply the 1st with a general direction of trowelling and the second on another (e.g. horizontalish, the verticalish), this might help with the flatness. Maybe I'll try this next time ! Simon.
But that doesn't alleviate the ridges which is caused by the trowel scraping the plaster ie the trowel is not getting swept across the plaster at the right angle.
The first coat is primarily to fill any deep undulations...this is allowed to partially set before the 2nd coat is applied - yes, some parts of it may be 12mm thick while others are only 2-3mm, but the wall would have to be seriously rough for this to be the case, thick artex for example. PB doesn't always need 2 coats - most pros give it 2 coats because it's easier to get a final finish, but if it's the only patch they're doing, they may just do it in one - if they are doing a full house or a few rooms, everything gets 2 coats because you have more time, IE you can first coat 2 walls, then with the next mix, second coat those and put 1st coat on a third, then trowel up the first two and your next mix will second coat the third and maybe get another wall first coated etc - in this scenario, doing it in one isn't really an option because it goes off too quick and your meterage is severely curtailed, inthat you can plaster one or two walls, then you can't mix again until they are completely polished up.
I'm not following this? - are you mixing the plaster too stiff? - it should have a pouring consistency....I can't think of anything in everyday life that I could use as a comparison - certainly not as thick as ready mixed polyfilla or tile adhesive, it should be able to drip....the only good beginners tip I can give you on mixing is to have clean water to start with, then sprinkle the powder in either by hand or by using a scoop...it will disappear below the water surface until there is enough powder that no water appears on the surface, then start mixing, either with a stick or a whisk
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