Uh oh, something is amiss here! Rust-Oleum Zinsser DIF Ultra Concentrate Wallpaper Stripper is a biodegradable, non-toxic and non-staining wallpaper stripper. Once the concentrate has been mixed with warm water, it is important to use the mixed solution immediately. The solution needs to be applied with a garden-type sprayer, sponge or roller. Do not use a fine mist sprayer. If the first layer does not peel off easily, score (10 holes per square inch) the surface and apply more of the solution. Allow DIF to penetrate for 2-5 additional minutes. Repeat the removal process and re-apply the stripper if necessary. To remove residual adhesive, re-apply the DIF solution, wait 2-5 minutes and scrape or sponge off.