Strange purple layer underneath paint on wall

[danieldodson]

Whilst stripping a kitchen wall today I found lots of this purple layer underneath the eggshell paint. Does anybody know what it is? I don't think it is a mold, there was some lime green mold near the floor (presumably from rising damp) and black mold in the corners near the back door.

 

[big-all]

no expert but as it is so uniform and not at all patchy could it be just a purple layer perhaps just paint

 

[JohnD]

How old is the house?

Is this a kitchen?

Edit
Yes it is

So it is an old oil paint, I think, intended to resist splashes of water or food, and able to be easily washed down or scrubbed.

IIRC you can remove it with a blowlamp and scraper, possibly a hot air gun, but it is hard.

 

[sparkwright]

Surely it's just very old coloured distemper, which old houses had usually when they were first built.

Does it sponge off with warm water?

EDIT. There does appear to be a lot of what appears to be new plaster there as well - so may be not distemper...

 

[danieldodson]

This stuff doesn't budge when attacked with a scotchbrite pad and hot water so I don't think it is distemper. The property is late 19th centuary, part of the Penant Llandygai estate in Bethesda, Gwynedd. The wall has been skimmed over with gypsum and undoubtedly that is ontop of rubble stone wall infilled with lime mortar and plaster. Not great and I should probably remove the skim and replaster with lime but time is a tight and council tax is expensive here since it is a second home so keen to get it lived in.

The paint that has been removed from the wall yesterday was done using a heat gun. Painstakingly slow but I wanted to get rid of the mold underneath the paint and give the wall a better chance to breath by removing the vinyl paint.

 

[JohnD]

. The property is late 20th centuary,

Surely not.

Late 19th, early 20th, more likely.

 

[danieldodson]

Surely not.

Late 19th, early 20th, more likely.

Indeed you are right. I've corrected my post.

 

[sparkwright]

Is the purple stuff dry, chalky, shiny, or what?

Probably something like John has described.

 

[opps]

How would the mould end up under the paint? Wouldn't it have simply penetrated through the existing emulsion? If so, then wouldn't it make more sense to use a paint that prevents the condensation mould from getting through the paint in the first place?

Most of the houses that I work in are circa 1900-1910 and have 9" solid brick walls. Many have exterior walls that have been re-skimmed with gypsum.

I often see people talking about the importance of using breathable paints. I have had no problems with regular acrylic/vinyl paints. You mention rubble filled walls- not something that I have come across. Does the rubble perhaps allow the ground moisture to bypass the DPC, thereby necessitating a "breathable" paint and lime plaster?

 

[opps]

The paint that has been removed from the wall yesterday was done using a heat gun. Painstakingly slow but I wanted to get rid of the mold underneath the paint and give the wall a better chance to breath by removing the vinyl paint.

A bit late now, but had you used cellulose thinners over it, if it started to blister/crack, then it would have been waterbased paint. Acetone, and to a lesser degree, meths will soften waterbased paints.