Andy Hide wrote:
|| Thanks for these tips. One thing I have noticed is that you polish up
|| the plaster and think you've done a great job. However, when the
|| plaster dries out and goes a lighter colour you see small areas (no
|| bigger than 10 pence piece in the worst places max) where it looks
|| like the plaster has not been polished up properly. I have seen this
|| to a lesser extent in pro's work too and can't figure how why this
|| happens.
||
|| This never happens to me on plaster board so I can only guess that
|| maybe the wall I am going over is not perfectly flat. As you polish
|| up
|| with the float you are missing tiny dimples in the wall as the float
|| is passing over them. Anyone else come across this ? Anyone got a
|| fix?
||
|| Andy.
||
|| (Andrew Gabriel) wrote in message
|| ...
||| In article ,
||| (Andy Hide) writes:
|||| Thanks for these tips. Another question though. If you are
|||| skimming a largish wall e.g. a hallway or stairs is it possible to
|||| split the job into two sections ?
|||
||| Yes. Pick a join line, plaster slightly over it, and before the
||| plaster has gone fully off, cut back the edge to a clean step, and
||| not feathered, as you can't feather in a join. If you know where the
||| join is, you will always be able to see it on the finished work, but
||| a good join won't notice unless you look for it. On many houses, you
||| will spot a join on the wall where the staircase is, as the
||| plasterer probably didn't do it in one go.
|||
|||| Skim dries out quite quickly and I don't think I
|||| could get a 4m wall done in time.
|||
||| Hum -- skim normally takes a day to dry out IME, much longer than it
||| takes to go off (set).
|||
|||||| Anyone have any tips for skimming onto old plaster? Managed an
|||||| almost perfect skim onto plasterboard but finding that old walls
|||||| are much more difficult. Any slight lumps and bumps mean that
|||||| the you are more likely to miss bits when trying to get a good
|||||| finish.
|||
||| Remove any obvious lumps above the surface.
||| The first skim coat goes on normally as thin as you can but should
||| leave the plaster level with the most proud bumps remaining on the
||| wall. i.e. you tend to scrape the trowl edge over the rough
||| surface, but it should leave you with a flat surface. The reason
||| for the second coat is that you can't polish this first coat
||| because of the background coming to the surface in places. So the
||| second coat is then put on ~2mm thick to give you clearance over
||| the most proud bumps on the background, and that's enough to enable
||| you to polish the surface.
|||
|||||| I primed the surface first with PVA which I think helped to
|||||| increase the working time. Total thickness of the skim was about
|||||| 2-3mm. Can you go thicker than this on old walls to help cover
|||||| up any imperfections ?
|||
||| Yes. The issue is that plaster finish coat shrinks when it sets. A
||| thin coat shrinks by getting slightly thinner which doesn't notice,
||| but a thick coat may crack.
|||
|||||| Applied in two coats, the second applied just as the first was
|||||| begining to set.
||||||
|||||| Also found that there were a few grit marks. Badly mixed plaster
|||||| ?
|||
||| Possibly. Check you aren't leaving unmixed plaster up the sides of
||| the bucket, only to fall in when you pour the plaster out. Other
||| sources of grit are from the wall (PVA should have stopped that)
||| or from adjacent walls/ceilings. I had fun plastering a wall up to
||| a ceiling artexed with small stalactites. The trowl edge would keep
||| breaking them off and dragging them into my plasterwork ;-)
|||
|||||| When ironing out the trowel marks as the plaster is setting does
|||||| anyone have any tips on which way to work across the wall.
|||||| Should you go top to bottom or left to right? Are long sweeps,
|||||| short sweeps better ?
|||
||| Generally inwards from all the edges. Keeping the edge of the trowl
||| parallel to the wall edge, start the sweep along the edge but in a
||| circular motion which sweeps out and ends a quarter turn later in a
||| direction perpendicular to the edge, but without turning the trowl.
||| When you aren't near an edge, it doesn't matter.

Bet you can't do a ceiling. lol. After the plasters dried coat the wall with
a thin mix of PVA, it helps a great deal if your Wallpapering over it.

--
Grouch