Fill a spray bottle with hot water and 1 tsp. of baking soda. Shake the bottle to mix the ingredients together. A teaspoon of liquid soap or 4 tbsp. of fabric softener may also work in place of baking soda.
Spray the solution on the wallpaper glue until it is thoroughly saturated. Let the solution sit for 10 minutes. The glue should soften and come loose during this time.
Scrape the glue off the wall with a putty knife. Hold the blade of the putty knife flat against the wall to reduce the chance of damage.
Tear off a 1-foot-long piece of aluminum foil.
Plug a clothes iron into an electrical outlet near the wall with the glue. Set the iron to medium-high heat.
Hold the aluminum foil against the glue. Depending on how sticky the glue is, the foil may stick to the wall on its own.
Move the iron back and forth over the foil as you would when ironing clothes. The glue should warm up and soften within 20 seconds.
Wipe the glue off the wall with a rag. Repeat the process on the entire wall until all of the glue is removed.
Add 1 gallon of hot water and 1 cup of vinegar to a bucket. Agitate the liquid with your hand to mix the ingredients.
Dip a sponge into the solution. Wipe a portion of the wall with the sponge to saturate the glue with the vinegar solution. Let the solution soak in for five to 10 minutes.
Wring out the sponge to remove the liquid. Scrub the wall with the dry sponge until the glue comes off.
Scrape the glue off with a paint scraper if it won't wipe off with the sponge.
Repeat the process until the entire wall is glue-free.