Walls must be carefully and thoroughly prepared in order to make paperhanging a complete success. New wallpaper slapped on top of old is by no means certain to stay up, and is likely to bubble and blister. The walls should be as even as possible, and completely clean and free of grease. Newly plastered walls containing lime can be papered if they are perfectly dry.
Coat the area with an alkali-resisting primer which will neutralise any active lime in the plaster. Alternatively, use one of the papers which have been specially treated for use on new plaster; a lining paper would be useful here. Distempered walls should be washed down with soapy water to remove all grime. Painted walls should also be washed down with soapy water to remove all grime. When dry, gloss-painted walls should be keyed by thorough scouring with coarse glasspaper (this slight roughening of the surface will help the paper adhere securely).
Previously papered wa1ls should first be stripped by soaking the paper well with warm water and an old distemper brush. A chemical stripper may be added to the water-but if the chemical splashes the paintwork, wipe it off straight away. While the paper is still wet, use the stripping knife to ease it off a little at a time. Properly soaked paper will come away from the wall easily and cleanly. Once all the paper is off, wash the walls with soapy water, rinse with clean water and, when dry, sand them lightly to remove surface blemishes, small pieces of paper, old paint drips, and so on.
Making good the walls
Fill any holes and cracks with a proprietary cellulose filler and when it is completely dry smooth it with glasspaper. The next step is to ‘size’ the walls. This prevents them from absorbing the paste too quickly, allowing time to position the paper on the walls correctly. To make size, dilute the adhesive you intend to use according to the manufacturers’ instructions (the packets usually give instructions for making it up for both size and adhesive). Coat the walls with it, using a pasting brush.