Little holes after sanding / painting

[LJB179]

Hello All, I had a flat renovation done last year but wasn’t happy with some of the work, so decided to sand and redo myself. I’ve noticed that in some areas there is a very uneven surface. This is sometimes already present and sometimes becomes present after I have sanded a wall down, where some of the wall has these holes in, whilst other bits are completely smooth or have stipple (before sanding). The below photo is actually not from a wall but some MDF boarding that was put up over pipes but this is the case in some areas of most of my walls.

Do you know what causes it? Adding paint layers seems to exacerbate the problem, in that the paint doesn’t fill these holes, they just appear deeper. I assume the solution is to sand and fill?

On the right hand side of this photo you can see stipple from the roller but on the right, these irritating holes that I cannot seem to fill with rolled paint no matter how much I try. I assume using a brush would resolve it by going into them but this obviously isn’t really feasible for large surfaces.

I’ve added a second photo of an actual wall, where you can see ordinary stipple at the bottom, then this weird texture with the holes in towards the top, and it’s like this all over.

Thanks!

 

[Wayners]

Some fillers when applied over dry filler will suck in quickly causing air to push out and you get pin holes.
To stop this fill. As filler is setting but still damp mix up more and fill again. Don't fill over dry filler basically.

Other problem is painting over dry filler. Depends on paint and filler. Some paints don't like dry filler so you need to prime the filler with a mist coat or a sealer like Gardz.

Also don't second coat emulsion too soon or first coat will pick up and you get an orange peel effect

 

[LJB179]

Some fillers when applied over dry filler will suck in quickly causing air to push out and you get pin holes.
To stop this fill. As filler is setting but still damp mix up more and fill again. Don't fill over dry filler basically.

Other problem is painting over dry filler. Depends on paint and filler. Some paints don't like dry filler so you need to prime the filler with a mist coat or a sealer like Gardz.

Also don't second coat emulsion too soon or first coat will pick up and you get an orange peel effect

Thanks Wayne.

Here are some better photos. On the left, this seems to be where painting has layered poorly. Is the solution here to do some wet sanding to even out the paint, and then repaint? Filling the whole thing would take ages and the level is already too high after too many layers of paint.

The second on the right is the wall straight from the work the guys I had in did. It looks the same as when I’ve sanded some walls back and these types of holes have formed. I assume the solution for those would be fill and sand the whole wall. Again, very time consuming, I’m assuming given that they’re along the whole wall to do it properly you’d want someone to skim them (which they were meant to do but looks like they cut some corners).

Thanks!

 

[accelerator]

What type of paint was used to paint the walls? And what type of paint are you using to paint over them?

 

[LJB179]

What type of paint was used to paint the walls? And what type of paint are you using to paint over them?

It’s all been Dulux Trade Vinyl Matt, so just water based.

 

[LJB179]

What type of paint was used to paint the walls? And what type of paint are you using to paint over them?

I think there are two causes. One might be from the workmen cutting corners with the skimming, creating bubbles, and the other (left hand photo above) is where I’ve layered on paint and it’s landed unevenly.

 

[LJB179]

What I’m really asking, whenever either of you gets a chance, is can this be resolved simply by perhaps wet sanding to even the finish? I did this before and it worked well, actually - it essentially moved some of the high spot paint into the pinholes and it was smooth. It did take an hour or so to do a small area and given that it’s MDF board behind I’m not sure if it was the best thing to do, but it worked. I don’t think it’d work on the other wall, where I think there could be issues with the skimming more than the painting, that probably required some filler or re-skimming but I wanted to ask the pros.

 

[accelerator]

I'm not a paint specialist, but my thoughts ...

I think it would be worth experimenting with some different paints, and also with drying conditions, i.e. how much ventilation you have, and using a room heater etc. It's difficult to get an idea of the scale of the holes, but I think if they're just small, say 2mm wide, then the stippling is being produced by the way the water-based paint you chose is drying. It's possibly drying to slowly, and this is causing it to coagulate and cause the holes. So, I would do some small experiment with both brands (I prefer to stick with water-based for environmental reasons), and with drying conditions, perhaps using higher room temperature to allow faster drying of the paint. Presumably, when you first put the paint on, it won't look like this, so it's the drying process that's doing it.

 

[LJB179]

I'm not a paint specialist, but my thoughts ...

I think it would be worth experimenting with some different paints, and also with drying conditions, i.e. how much ventilation you have, and using a room heater etc. It's difficult to get an idea of the scale of the holes, but I think if they're just small, say 2mm wide, then the stippling is being produced by the way the water-based paint you chose is drying. It's possibly drying to slowly, and this is causing it to coagulate and cause the holes. So, I would do some small experiment with both brands (I prefer to stick with water-based for environmental reasons), and with drying conditions, perhaps using higher room temperature to allow faster drying of the paint. Presumably, when you first put the paint on, it won't look like this, so it's the drying process that's doing it.

Sounds like a very reasonable assumption. I think I know why in that case - behind the boxing are water pipes, sometimes hot. The issue seems to persist plainly down the middle of the boxing, which is where the pipes are.

 

[LJB179]

I'm not a paint specialist, but my thoughts ...

I think it would be worth experimenting with some different paints, and also with drying conditions, i.e. how much ventilation you have, and using a room heater etc. It's difficult to get an idea of the scale of the holes, but I think if they're just small, say 2mm wide, then the stippling is being produced by the way the water-based paint you chose is drying. It's possibly drying to slowly, and this is causing it to coagulate and cause the holes. So, I would do some small experiment with both brands (I prefer to stick with water-based for environmental reasons), and with drying conditions, perhaps using higher room temperature to allow faster drying of the paint. Presumably, when you first put the paint on, it won't look like this, so it's the drying process that's doing it.

That said, not sure what’s going on with the wall, as that is a different issue. Maybe the plastering / skimming wasn’t left long enough to dry, or wasn’t laid down well, is my guess.

 

[OhYeah]

If that hole was big then you might need 3 times to use filler on that wall each time you use filler sand it and clean it with a dust brush and after use mist coat and don't rush it to use filler or mist coat even they say it takes 2-3 hours until it dry the filler or the paint i will advice you wait 12 hour .

 

[foxhole]

Filler need mixing well , dry particles not mixed with form holes as it dries.
Sand back with 120/180 paper .

 

[opps]

As above, you can sand the paint, but you really need a D/A sander connected to a dust extractor (read: vacuum cleaner). The dust extractor will help reduce the possibility of the paint overheating and gumming up the paper.