Stubborn stains: Rub one of the cleaners recommended for regular cleaning on stained area; leave on about an hour; rinse.

Heavy soap scum buildup: Occasionally use a mild abrasive, such as "Bon Ami" or "Soft Scrub"; do not use them for regular cleaning.

Hard water mineral deposits: Occasionally remove with products specifically designed to remove such deposits that state on label they are safe for fiberglass; these are usually mild acids such as "Lime-Away" which contains some phosphoric acid but is safe for consumer use; rubber gloves should be worn when applying, and label instructions followed exactly.

Tough stains such as tar, adhesives, oil paints, etc: Moisten clean cloth with a solvent such as acetone (nail polish remover) or paint thinner and rub stained area lightly until stain disappears. Use the minimum amount of solvent needed. Do not let solvent go down drain or touch any plastic items. Wipe off with clean cloth dampened in water. Be very careful using solvents. Do not use around heat or flame, do not smoke, keep container capped, have plenty of ventilation!

This article was written by Anne Field, Extension Specialist, Emeritus, with references from Wisconsin Extension bulletin Maintaining Your Home - Care of Bathtub Enclosures.