Andrew Gabriel coughed up some electrons that declared:

In article ,

Some thoughts...

It's actually only talking about skimming, which is only part
of plastering. Would make more sense to name it something with
skimming in it, unless you intend it to cover plasting eventually.
It may make sense to cover scratch coat plastering in a separate
article anyway -- they're reasonably different.

OK - Perhaps it could be renamed. I was thinking about adding something
about undercoat plastering on various surfaces as I encounter them.

PVA isn't used when applying plaster to a surface which is
still wet from itself being plastered or sand+cemented. (This
means still initially wet, and not as a result of you wetting
it, which doesn't count.) Sand+cement must be left for 24 hours
before being plastered, but plaster should be recoated same
day if possible. If you miss this deadline, you may need to
leave it to dry and then use PVA.

OK - thanks, I can certainly add that in.

I don't agree with not properly flattening the first finish
coat. If you slap a second coat on too soon, and without doing
this, you're really just working with one thick coat, which is
going to be harder to keep flat and even.

I should mention that I'm only responsible for the second method that does
flatten the first coat off, before applying the second. I didn't feel
qualified to pass judgement on the first method which was already there.

Could do with a description of what the various coats are for...

Scratch coat (under coat) is to give you a flat, vertical
(horizontal for ceiling) surface, regardless of the undulations
of the underlying wall.

Ah - OK. If I can just nick that verbatim more or less, I can add it.

Would you use a derby (or long bit of wood) on the undercoat to achieve
flatness?

I'll stress again, I'm probably the wrong person to write a plastering wiki
bacause I'm basically clueless - I just though it might be useful to add a
true beginner's perspective.

:-

But I can copy n paste!

The finish coat is to give you a smooth finish over the scratch
coat. Two coats are required. The first gives you a smooth
surface by bringing the level of the whole wall up to the level
of the highest peaks on the scratch coat. This should be leveled
more than you suggest, but it can't be polished because the high
points of the scratch coat will be on the surface of it. The
second finish coat gives you headroom over all of the scratch
coat peaks, which means you can polish it without hitting hard
bits.

In Mixing, it's important not to go OTT with a power mixer.
In particular, you mustn't wisk air into the mix,

Yes - I did get a bit of this. But the air bubbles smoothed out fairly
easily. It's this or 100+ quid for a real mixer I'll try the SDS on a
slower setting next time.

and over-
mixing will also make it go off quickly.

Hmm - I might have seen that. One mix did seem to be setting faster than the
others - I had a fight to get it on the wall before it started going.

A proper power mixer
is much slower than most drills, and has low gearing. The
risk with using a drill is that you need to run it slowly,
and unless it has a good low gear, it won't blow enough air
through the motor to cool it given the high load imposed, and
it may overheat. You can mitigate this somewhat by taking off
the stirrer/chuck, and running the drill at top speed with no
load, which will cool it down. Do this as a matter of urgency
if you start smelling hot motor (don't just turn it off and
leave it to cool on its own). Do remember to take the stirrer
off first though!

Sound advice. I think my 8kg Aldi has such an high thermal mass that it
doesn't care. But if using a more normally sized drill it could be a
problem...

In Cleanliness, the other important thing is that bits of plaster
from you last mix, if allowed to contaminate the next mix, will
make it go off more quickly and less controllably. So it's
important to thoroughly clean all the tools between mixings
(particularly if you're a beginner). As you say, plaster
washings can go on the garden (I chuck it over the lawn), but
mustn't be poured into the drains.

That would be bad (TM)

If you don't have a garden
area, pour it into a large tank or drum so the plaster sinks
and sets at the bottom, before pouring off the water.

OK.

Thanks for the comments Andrew - I'll work them in...

Cheers

Tim