I filled and sanded defects in walls (plasterboard) previously painted and applied two coats of plaster sealent. I then applied two watered down coats of cheap matt emulsion to erase the old colour. I then apllied a coat of Dulux matt emulsion and allowed to dry but didnt care for the colour (typical woman thing). I then applied a coat of Dulux washable matt emulsion - all fine. I applied a second coat and whilst doing so notice it was bubbling in places (tiny bubbles) which i've burst, filled and sanded and wondering now how to proceed, i don't want to repaint and the same thing happens again. Did i not leave enough time to pass before applying second coat, i went with the tin reccommendation of five hours !. I've read in some forums that a oil based primer would eradicate future bubbling of water based emulsion. Is the way to proceed !. Any advice welcome.
when you say tiny...? all over the wall? are they in the areas where you filled and sanded? if so did you remove the dust from the surface prior to painting? could be caused by your rollering technique... more info required for a better answer.
solvent based primer is worth a try at the very least. with regard to drying times, if you followed the manufacturers' instructions then it should be fine unless you were painting in cold, west highland temperatures! five hours is a decent drying time for a water based emulsion.