A few years ago, I decorated my son’s bedroom but the emulsion on the walls came up with lots of small bubbles. I left it at the time but I am now decorating the room again. I’ve scraped off and rubbed down the bubbles and applied my new paint but it’s still bubbling. In fact it’s worse. How can I solve this problem? Should I rub off the bubbles again and apply a primer before the emulsion? If so, which would be the best for this problem? How many coats of primer? Or is there a better solution? The room is 3m long x 2m wide x 2.2m high. Thank you