Quick Question re: touch-up

[Leon125]

Hi,
When plastering, sometimes, even after 2 coats, there are unfortunately small gaps/dents.

So I figure the best thing to do is mix a small batch and use a small trowel to patch up where the gaps are.

Am I right in thinking patching up gaps only needs one coat however ? And that there is no need for a second coat over the correction ? Or do I need two coats so it blends in with the rest of the wall ?

Thanks

 

[RandomGrinch]

Quick answer!
As a DIY'er who has done a small amount of plastering, I would normally put a mist coat on (that really shows up the imperfections!), then just use filler!
This does work best if the imperfections are relatively small!
It's probably a bodge, but it works for me

...and if you are going to patch the plaster, make sure you moisten down the area well, or the water will be sucked straight out of your patch and you'll be left with a crumbly mess!

 

[Leon125]

Thanks Grinch that's really helpful . Ive included examples of the sort of thing Im trying to fix.

Figured some filler would help, but definitely good to know about the mist coat bit. Presumably a 50/50 water ratio would be ok here ? (Not applied mist coats before)

Or...Could I just use filler and then sand down ?

Thanks once again for your help. Will remember the point about moistening the wall (can i apply diluted pva) ?

 

[RandomGrinch]

New plaster sucks in water like a sponge. If you apply filler straight onto it, it will absorb all of the water out of the filler before it can bond. The mist coat forms a seal that helps reduces the absorption.

Did you leave the first layer of plaster to dry before putting on the top coat, or was it a really hot day?
It looks like the problems you had are related to areas of the plaster drying out too quickly.

 

[Leon125]

Thanks again Grinch. And yes, it was a really hot day (earlier on this year).
So it sounds like I shouln't have taken so long over the first coat. It might have been a little over 30 mins, not by much.
Daft question I know but shouldnt it all eventually dry out to the same level eventually ? I thought as long as it was flattened out then it would be ok, but obviously not.
To stop drying out too quickly, I guess its more pva. Also, in future, I might try adding citric acid as ive heard it slows things down a bit,

 

[RandomGrinch]

Don't worry about the PVA!
Some will say it's a mistake to use it at all!

I'm no expert, so don't take this as gospel!
I've had a similar problem, and it was caused by the first layer drying out too quickly before I applied the second.
Because patches of the first were already drying, this sucked the moisture out of the 2nd coat and caused small patches of this to become crumbly. I didn't notice until I tried to trowel up. When the trowel went over the problem areas, it just dragged these clumps of dry plaster out of the wall!
In hot weather, dampen the wall down before applying the next layer.

Alternatively, perhaps the plaster wasnt mixed thoroughly? These could be areas where unmixed dry clumps were buried in the layer?

Anyway, I maybe completely wrong.
It might take some work, but I'm sure it will look good in the end!