Removing stubborn glue from a fiberglass shower insert requires careful application of products and careful scrubbing to prevent damage to the surface. Glue is typically used to install sliding shower doors and to mount fixed shelving inside the shower cubicle. Removing shower doors or shelving requires removal of the strong sealant glue as well. Let's look at some methods to remove the glue from fiberglass shower insets with typical solvents around the home, as well as items that can be purchased at the hardware store.
Use the plastic putty knife and apply gentle force to the larger areas and strip of glue. Most shower insert glues are silicone-based to provide a very tight seal to prevent water penetration. You may be able to push some of the glue free with steady pressure to the plastic putty knife. Don't use a metal putty knife, as you will mar the insert's surface.
Spread a layer of vegetable oil to the glue. Vegetable oil works to break down the glue for easier removal. Combine this method with the use of the putty knife to clear the glue from the insert.
Soak a rag with mineral spirits and place the solvent on the glue. Allow the solvent to work on the glue. Mineral spirits are used to thin and remove oil and acrylic-based paints.
Apply a thin layer of acetone to the glue. Acetone (nail polish remover) will help dissolve the glue for easier removal. Acetone is primarily used as a degreaser. Test acetone in small quantities to check for damage to the fiberglass insert. Acetone is used in industry to thin fiberglass resin.
Apply commercial products such as Goo Gone, an oil-based glue remover. This product has a pleasant citrus smell and will soften the glue. You will still need to use elbow grease to remove the glue, but this product should soften it enough to make removal easier.
Apply silicone remover to the glue for easier removal. One brand is 3M General Purpose Adhesive Remover.
Squirt WD-40 lubricant on the areas of glue to soften the dried product and help make scraping the glue off easier. Give the oil time to penetrate the glue before attempting removal.