With this technique, you make horizontal slits in the surface of the old wall covering with a utility knife, a razor blade, or a special tool called a paper stripper, available at wall covering stores. The slits, made eight or ten inches apart, allow warm, soapy water or a liquid paper remover to get behind the paper and soften the adhesive so you can pull or scrape the paper off plaster walls. You can apply either solution with a sponge or a spray bottle. Caution: If you spray on a liquid paper remover, use a painters' mask to keep from inhaling chemical vapors.
Step 1: Apply the water or the paper remover and let it soak in for a few minutes.
Step 2: Do the same thing on the next strip, then go back to the first and wet it again top to bottom.
Step 3: Use a 3 1/2-inch-wide wall scraper with a flexible blade to begin stripping. Slide the blade under the top edge of one of the horizontal slits and, holding it at about a 30-degree angle, push up on the wet paper. A scraper-width section should rip along the sides of the blade and wrinkle up above it as you push.
Step 4: Continue pushing as long as the paper comes off. If the strip of scraped paper breaks, resoak that area and start scraping at another slit. If, after repeated soaking and scraping attempts, the adhesive is clearly not yielding, you'll have to use another method.
On walls made of drywall, use a paper stripper to make the horizontal slits as before, but don't wet the paper. Just slowly scrape or peel it away from the wall.