OLD HOUSE DIYer

How to deal with decades’-worth of grime on various types of glass you may encounter in an old house.

Glass-cleaning solutions for hard jobs you’ll encounter during restoration.

Intractable dirt on a pressed-glass transom . . . panes blacked out in paint on the Queen Anne window in a skylight: just two of the glass-cleaning dilemmas OHJ editors have faced in our own restorations. Etched glass may be filthy and yet delicate, windowpanes may be dirt-embedded to the point of pitting. Or maybe you’ve just waited too long to clean the lights in the garage door. Start with a proprietary glass cleaner, but know that other methods come in handy, too.

Cleaning Glass REALLY FILTHY GLASS

Wash glass with the vinegar solution, applied with a soft cloth and squeegeed off. Spray on glass cleaner with a clean cloth and follow by rubbing with newspaper. (Try Windex with ammonia, or a commercial preparation.) If a stubborn haze from mineral deposits is left behind, apply a glass-cleaning compound such as CLR Sparkle; apply vigorously in a circular motion with a new clean cloth. Let dry. Buff with a clean cloth.

PAINTED-OVER GLASS

If it’s just drips or smears, wipe the paint with a damp cloth to soften, and use a utility knife with a flat blade to scrape them off. For painted-over glass, first mask the frame and putty seal with painter’s tape. Wearing rubber gloves and safety glasses, apply a solvent such as Oil-Flo or SoSafe (graffiti remover). Scrape off remaining paint. Stubborn areas of stuck paint and embedded grime may come off easily with an application of oven cleaner (lye) formulated for use on cold ovens. This is caustic stuff so take precautions and work in a ventilated space. Sponge and wipe until clean, then neutralize with the vinegar solution.

PRESSED GLASS

The textured surface of pressed glass collects grime that doesn’t simply wipe off. Try a two-step process. 1. Using the vinegar solution, aggressively wash the window, or use a Mr. Clean Magic Eraser. 2. To get into the recesses and whorls, use a toothbrush or small, soft-bristled brush; dip into baking soda to add a gentle abrasive. Wipe and assess. If grime remains in the pattern, use the dish-detergent solution and repeat the toothbrush process. Rinse with a clean, damp cloth, and dry with a lint-free or microfiber cloth.

ETCHED/CARVED GLASS

Mix up the dish-detergent solution and apply with soft car-wash brush or sponge. Squeegee. Spray glass cleaner on any spots and wipe with soft cloth. Never use paper towels on etched glass as it leaves lint. For stains from mineral deposits, use the vinegar solution: wet a soft cloth and gently scrub. Dip cloth in baking soda if necessary for gentle abrasion. Rinse and squeegee dry.

STAINED/PAINTED GLASS

Paint on glass is easy to scratch or even remove. Don’t use ammonia or vinegar. For stained glass, mix a gallon of distilled water with a couple of squirts of pH-neutral, non-abrasive dish detergent (e.g., Seventh Generation Natural Dish Liquid). Microfiber cloths work well: Wearing rubber gloves, dip cloth in solution and wring out so it is damp, not wet. Work from the top of the window downward. Wipe a section and dry with another clean cloth. Use cotton swabs dipped in detergent mixture in corners. After working on leaded glass, toss gloves and rags away. For painted art glass, use de-ionized water to clean. Make a large swab of bamboo skewers wrapped in raw cotton. Gently roll the lightly dampened swab over a section of painted glass. Let dry. Further cleaning may require a professional conservator.