Preparing plaster walls for painting

[Tomw84]

I've stripped some wallpaper from my living room to find there's a layer of paint underneath that's dusty (it comes away on your fingers when you touch it) but fiendishly difficult to get off the wall. I've tried using warm, soapy water and a sponge, then had a go at sanding. Both work, but very slowly - I've been scrubbing/sanding for a couple of weeks and reckon another couple of weeks would see it finished - but to be honest I'm bored, and wondered if there's some sort of magic product you can use on dusty walls to ready them for painting. Any recommendations?

 

[motorbiking]

You could try diluted matt emulsion to seal it in, but I think the best option is to buy a random orbital sander and keep going, then wipe the walls down with a damp cloth.

 

[JohnD]

How old is the house? Is the plaster creamy white?

Try scrubbing a test patch with kettle-hot water, and rubbing it off with a rough old towel.

Distemper? The glue dissolves in hot water but not in cold. It has a distinctive smell. It is usually in pastel, chalky colours.

 

[Tomw84]

How old is the house? Is the plaster creamy white?

Pretty sure it's late '40s/early '50s.

The plaster is a speckled grey, like this:

Try scrubbing a test patch with kettle-hot water, and rubbing it off with a rough old towel.

Distemper? The glue dissolves in hot water but not in cold. It has a distinctive smell. It is usually in pastel, chalky colours.

Would a steamer work? I'd never heard of distemper, but yeah, I think that might be what I'm dealing with here!

 

[Tomw84]

You could try diluted matt emulsion to seal it in, but I think the best option is to buy a random orbital sander and keep going, then wipe the walls down with a damp cloth.

I do have a ROS, but I'm gonna be sanding the floorboards in a few weeks and don't want to wind up the neighbours too much just after moving in! I'll bring it out to tackle any stubborn holdouts once the rest of it is off.

 

[JohnD]

Try the hot water first.

Sadly I have worked with distemper quite often. I don't like the smell. The glue is made from the boiled up hooves of dead horses, mixed with powdered chalk and water colours.

A steamer can burst gypsum plaster, but I don't know that it will affect lime. Hot water scrubbing is usual for distemper.

 

[motorbiking]

that looks like a sand/cement seraphite plaster. Its fairly tough and wont blow as easily as gypsum.

 

[JohnD]

I just looked up animal glues, and apparently they soften in water between 50C and 60C, and set below 50C

We used to work with kettles to keep topping up our buckets. It settles into sludge at the bottom of the bucket. The water has to be too hot to hold your hand in.

You need the hot water to wash it off so I don't think steam alone would do, though you might scrape it off.

 

[Tomw84]

Thanks both! I've already been over the walls once with a steamer to get the wallpaper off, so they should be fine, but I'll give the hot water scrubbing a go first!

 

[Tomw84]

Steaming then going at it with a sponge has worked pretty nicely!

What I'm left with though is faint wisps of paint across the plaster, as in the photo attached. Do you think I'll be able to paint over these, or will the residual distemper still cause problems?

 

[JohnD]

don't know. I've only scrubbed distemper off cleanly and rubbed with aan old towel.

why won't you scrub it?

 

[Tomw84]

I have been - steamer to heat the paint, then scrub at it with a scouring pad, then wipe it off with a sponge. That gets about 99% of the paint off easily, but the last 1% is stubborn.

 

[Wayners]

I dustless sand walls like that with 80 grade mesh.
DIY person could use the cheapest DIY orbital and duck tape it to vacuum for similar result.

When done apply a coat of gardz to seal

 

[Tomw84]

Try scrubbing a test patch with kettle-hot water, and rubbing it off with a rough old towel.

You were spot on - all I needed was a decent scrubber instead of a cheap scouring pad from the local corner shop!

Reckon I'll have both rooms done by the weekend now - happy days!