Emulsion crazing/cracking - help!

Hi, some help with this one would be greatly appreciated.
I am in the process of re decking the living room with a coloured dulux Matt emulsion.

My problem started when I decided to try and cover up some dark tester patches that had been painted on the wall with polycell stain stop (won't be doing that again!) On the first two coats of emulsion the patches of stain stop were showing through. Closer inspection revealed them to be slightly raised so out came the glasspaper followed by 2 coats of dulux Matt White elmusion to flatten the wall off. This seemed to work although I did notice the areas that had the polycell treatment took ages to dry. Next cane two coats of the coloured Matt emulsion which brings me to my problem- crazing or cracking just on those small areas. I tried a light rub down followed by another coat, and no joy.

I am at the stage now where I want to make sure I get it right whatever I do next. I have read that an oil based undercoat may be best; will this work on patches, if so what's the best way of applying this? I just dont want to be back with the patches again! Should I be doing anything different when applying the emulsion, apart from leaving ages between coats? BTW the walls have only been plastered in the past 5 years so I really don't want to go down the paper route!

Sorry for the essay, just thought it best to give as much info as possible! TIA

Try stain blocker which is spray one, it dries in about 15 minutes.

Sand back the crazed areas and apply one coat of slightly thinned oil based undercoat,
If any face filling is then needed apply and lightly sand the filler, then apply a mist coat to the filled areas prior to your finish coats.

Dec

Thanks Dec, despite the hassle it worked a treat!

a note for next time, use tester pots in an inconspicuous area not in the middle of a wall!!

I doubt that the testers here were to blame, more like what was painted over them.

Dec

fair point just pointing out that people tend to paint perfect squares with the testers and leave fat edges that need attention prior to emulsion. doesn't look as bad in an inconspicuous area if not addressed properly!

Yes that can happen, so far better to apply them to a piece of card and not the wall.

Dec