Polystyrene ceiling tiles

[bamboo]

Hi
I'm redecorating a 1950's semi with 1970's decor. I've removed all the horrible polystyrene tiles from the ceiling and I'm left with a sea of large blotches of glue. I've attacked them with the hot air gun and a scraper - it's smelly and makes me nauseous. Is there an easier way of removing the glue? I'm intending to have the ceiling plastered. Is it possible to plaster over the glue?

Any advice appreciated.

 

[spice]

I find the wall paper steamer very good, if you have already tried putting a wide blade stripping knife underneath the blobs, and it hasnt come off, then the wall paper stripper will definately help.