Wallpaper removal necessitates softening the old wallpaper paste. Score the paper and use a wallpaper stripper. Some people try vinegar, but the job needs more. Do not paint over the old wallpaper unless you want to create even greater problems in the future.
To soften the wallpaper paste you need two things:
1. A quick and easy product that will react with the old wallpaper paste.
2. The ability to get the product through the wallpaper and soften the paste.
I recommend scoring the wallpaper to allow the removal solution to penetrate and work faster on the old paste. A scraper or coarse sandpaper will do a tolerable job but a Papertiger scoring tool will perforate the wallpaper quicker and easier. It has cutters on a tool that allow you to make circular movements across a wall perforating the wallpaper surface so the remover can penetrate.
The stripper of choice is Dif concentrated wallpaper stripper. It has an enzyme that softens wallpaper paste better than my old ‘home brew’ of vinegar and water. Mix one part Dif concentrate with eight parts hot water and apply it with a kitchen mop or by hand with a sponge. For large areas, use a tank sprayer for quicker and more even coverage.
Cover an entire wall with the enzyme and let it set for 10-minutes before coating the next wall. After coating the second section, take a plant sprayer with hot water and spray over the first area. To make Dif stay wet longer add a small amount of fabric softener to the mixture. Once the product has been on the wall for 20 minutes, try a scraper and test to see how the wallpaper paste is doing. The paste should be softened and removal should go quickly.
While you are stripping the first wall, spray hot water on the second wall to keep it wet and the Dif working. You will find the last section you strip will be the easiest. Time is your friend. Take a lesson from this now and let the product work so you do not have to.
Another tip is to try to peal the face of the paper off first. Remove the easy stuff first, then the water and enzyme can more easily absorb into the glue.
Wallpaper scrapers come with three or 4-inch razorblades that work well when scraping the paper off the wall. Zinnser makes a Paper Scraper that holds the blade at the proper angle to reduce gouging.
There is another wallpaper removal product called DIF GEL that works well for clay-based adhesives. It comes ready mixed in a 32-oz sprayer or in a gallon that can be brushed, sprayed or rolled. We recommend it when the Dif concentrate does not do the job.
Amateur painters take special note; if you leave any wallpaper paste on the wall it may come back to haunt you later.
What happens is that when the primer is applied over wallpaper paste, but the paste can melt into the latex primer. Both products can dry together leaving the illusion everything is all right. When the finish coat of latex paint is applied, the primer and the paste can melt creating a giant mess.
Ask any painter, they wash and rinse a stripped wall thoroughly. They know proper preparation will save many hours of later rather than saving 10 minutes now.