vinyl matt not sticking

[mcmook]

i'm in the middle of painting a large room (a shop) with dulux trade vinyl matt. the walls are victorian tonge and groove panelling, which have been sanded and primed. this was done a while ago and unfortunately i can't recall what was used to prime the boards. as i'm painting it small patches fail to stick and blister and when it dries these flake off. this has happened over a lot of the are, though some areas seem fine. anyone know whats causing this and what the remedy is?

(ps is vinyl matt the same as matt emulsion?)

thanks

[John Rumm]

Sounds like the surface is contaminated with something. Perhaps a wash down with sugar soap or a light sand would help.

Not always - its usually washable, ordinary matt may not be.

[mcmook]

thanks - what im most worried about is whether the blistering is isolated to those places it already has or whether it will continue in the future. i asked for advice at the dulux centre and i think i may have the (part of the) answer ... we used trade paint my wife and her friends did the painting i told them to thin it down with water but i dont think they believed me! and used it straight out of the tin. it was too thick. i used the same paint and thinned it down on some plasterboard with a mist coat already applied and the application and finish were very good. so its probably a combination of a poor surface and too thick paint. hopefully whats already stuck will stay stuck and i'll spot treat the other affected areas.