Barrettine Wallpaper Stripper 500ml. Concentrated wallpaper stripper which requires dilution with warm water. Designed to make stripping wallpaper easy and painless, 500ml of concentrate will create 4.5 litres of stripping liquid. Apply with a sponge or roller into the wallpaper, scoring the wallpaper before hand will help the liquid penetrate and is essential with washable wallpapers. Leave for 5-15 minutes to take effect then remove wall paper with a scraper. For several layers of wall paper repeat this process.