How to Prep Fiberglass for Paint

While most fiberglass is purchased prepainted, some manufacturers sell products that can be painted to match the decor. Many exterior doors are made of fiberglass, and manufacturers have made these doors easy to clean and paint. If possible, you should purchase a new door that has instructions from the manufacturer to ensure proper cleaning and painting techniques are followed. If the door has already been stained or painted, a strong chemical stripper must be used to remove the top coat before painting. Keep in mind that this technique should not be used for fiberglass tubs or sinks.

Things You'll Need

• Dishwashing liquid
• Warm water
• Sponge
• Mineral spirits
• Respirator
• Eye protection
• Nitrile or neoprene gloves
• Polyethylene or ethylene vinyl alcohol gloves
• Long sleeve shirt
• Long pants
• Methylene chloride
• Rag
• Watch
• Clean cloth

Instructions

Prepping New Fiberglass

1. Clean the surface using a mixture of 1 tbsp. dishwashing liquid to 1 gallon of water. Use a sponge to apply the cleaning solution. Use mineral spirits to remove surface stains that are not easily removed.

2. Rinse the fiberglass surface with clear water. Be sure to remove any remaining dishwashing liquid residue.

3. Allow the fiberglass to air dry completely before proceeding. If possible, move the fiberglass into a room that is temperature controlled; fiberglass paint reacts badly to extremes of temperature.

Prepping Previously Stained Fiberglass

1. Put on a high quality respirator, eye protection that will guard against chemical spills, and two pairs of heavy gloves. The outer pair of gloves should be made of nitrile or neoprene. The inner pair of gloves should be made of polyethylene or ethylene vinyl alcohol. Be sure to wear a long sleeve shirt and long pants while working.

2. Apply methylene chloride to a small area of the stained fiberglass using a rag. Wait exactly two minutes, looking at a watch to verify the elapsed time, then remove the stripper with a clean cloth. The goal is to remove only the clear top coat that will prevent the new paint from adhering. Complete this step in a well-ventilated area.

3. Continue applying methylene chloride until the entire area has been stripped of the clear, protective top coat.

Tips & Warnings

• If you feel uncomfortable working with methylene chloride, talk to your local auto body shop. Many shops have the facilities to safely strip and paint fiberglass and will work on items other than cars.

• The vapors from methylene chloride have been shown to cause cancer. Be sure to wear a respirator, eye protection, and gloves when using this chemical. Methylene chloride can cause a burning sensation when touching the skin, so long sleeves and pants are also a must.

• After using methylene chloride, wash your face and hands carefully before eating or drinking.

References

• Ask the Builder: Fiberglass Paint Stripper
• Ask the Builder: Painting Fiberglass Doors Black
• Ask the Builder: Painting Fiberglass Doors & Finishing Tips
• Occupational Safety and Health Administration: Methylene Chloride Facts No. 7