Removing wallpaper is no easy task, and even after you have all of the paper down, the dried paste is often left on the walls. In order to paint or apply new wallpaper, you must remove the old paste. The good news is that the hard part is done once you have the paper off -- removing the dried paste is a quick job with the right products and methods.
Fill an empty spray bottle with a wallpaper removal solution. Don't waste money buying a commercial wallpaper stripper. Make your own by mixing 1 litre (32 fl oz) of hot water with the liquid fabric softener or baking soda. Put the lid on the bottle and shake.
Spray a generous coating of the wallpaper removal solution on the paste residue. Let it sit for 10 minutes, and then use a putty knife to scrape off the glue. Wipe off the putty knife with a rag after each scrape.
Continue this process of spraying on the solution, letting it sit and then scraping off the dried paste until all the paste is gone.
Fill a bucket with 4.5 litres (1 gallon) of water as hot as you can stand it. Add 500 ml (2 cups) of white vinegar.
Dip a sponge into the bucket and wring it out. Wash any remaining residue from the walls with the sponge and vinegar solution. Rinse and wring out the sponge often. Let the wall air dry completely before you apply paint, wallpaper or any other type of treatment.