Size/seal new plaster before wall papering

As new plaster is porous a wall size is recommended before wallpaper this will make the movement of wallpaper easier when you start to apply it to the walls. This comes in a packet mixed to a paste.

You can actually buy a product called size wich you apply before wallpapering or apply a thin mix of paste

You have got 2 options you can use wall size. But It has an odour which does not smell very nice until it dries. Or you can mix 40% wallpaper paste to 60% water

there are a number of ways to deal with this. you can size the bare plaster with the same paste as you will use to apply the wallpaper. also you can bond the area first with a solution of pva and water (10% pva to 90% water) and allow to dry before applying wallpaper. another way would be to paint the bare plaster first with normal emulsion paint diluted to around 50% water to 50% emulsion. if none of these are applied first you will get a condition known technically as "snatching" when applying the wallpaper. because the untreated plaster is so porous it will literally "snatch" the wet paste from the newly applied wallpaper making it very difficult to "slip" when attempting to match the pattern and causing the paper not to adhere properly to the wall.

I would either mix the wallpaper paste to about 49-60 and use that to size the wall but my best option would do the same with vinyl Matt paint and seal your wall that way , try it !! Regards Francis

the best way is to use a product called cannons glue size mixed with hot water, you should have no problems after that.