Corroded Leaded Windows

 

Cleaning Corroded Leaded Glass

by Judy Heldreth-Miller

How to clean rusted joints

To clean the rusted or oxidized came joints on your leaded glass window, you must avoid household vinegar, baking soda, and harsh acids, which can cause a chemical reaction that creates a white powder (basic lead carbonate) and breaks down the metal.

Because the channel framework (came) is typically made of lead or steel-reinforced lead, safety and gentle abrasive action are key to removing rust without scratching the antique glass.

Required Supplies

1). Safety gear: Heavy duty rubber gloves and an N95 respirator mask (lead dust is toxic).

2). Lubricant: Linseed oil or a speciality cleaner like Kwik-Clean Stained Glass Cleaner.

3). Abrasive tool: Fine brass wool or a brass wire brush (do not use coarse steel wool, which can leave behind steel particles that cause future rust).

4). Absorbent powder: Whiting powder (calcium carbonate).

5). Finishing touch: Novacan Black Patina and Clarity Stained Glass Finishing Wax to seal it. [I would not advocate the re-introduction of acid (patina) after the cleaning. Stephen Richard]

Step-by-Step Restoration Process

1. Wet and Scrub the Metal Joints

Put on your respirator and gloves. Apply a lubricant directly to the rusted joints using linseed oil or a liquid glass cleaner. Never scrub lead dry, as it creates airborne toxic dust. Gently scrub the joints with your brass wool or a soft brass brush. Brass is softer than glass, so it will remove the rust and tarnish from the lead without scratching the pane surfaces.

2. Lift Leftover Oils and Gunk.

Sprinkle whiting powder generously over the damp areas. Use a clean, dry natural bristle brush or a microfiber cloth to work the powder along the came lines in circular motions. The powder absorbs the dirty oils, lifts residual rust slurry out of the tight crevices, and naturally polishes the glass. Wipe or vacuum the spent powder away.

3. Re-Darken the Lead (Optional)

The cleaned lead joints will appear bright, silvery, or uneven [in colour]. To restore the historic dark finish, use a toothbrush to brush a small amount of Novacan Black Patina directly onto the clean metal. It will turn the metal black instantly. Wipe clean immediately after application. [I would certainly omit this, as it introduces an acid again. The came can be darkened again by simple brushing with a soft shoe polish brush. Stephen Richard]

4. Seal with Wax to Prevent Future Rust

Apply a thin coat of 100% carnauba-based Clarity Finishing Wax across the entire lead structure and adjacent glass using a soft cloth. Let it dry to a light haze for a few minutes, then buff it off with a clean microfiber cloth. The wax leaves a water-resistant seal that prevents moisture from reaching the joints and restarting the oxidation process. [Although this is a short term protection in relation to the longevity of leaded glass windows. Stephen Richard]