How do you clean leaded stained glass windows?

How do you clean leaded stained glass windows?

Just like anything else leaded stained glass windows need cleaning. But why do they get in the state they do? Why does the lead age like it does?

Let’s have a look at what’s happened to our leaded lights over the last century and what we can do to them to tranform the like the glass below by using a few things you’ll find in the kitchen or online for a few quid.

Oxidation of leaded windows

Firstly, let’s understand why lead goes blotchy and eventually take on a dark grey matt patina.

Remembering that the lead in leaded windows is probably 120 years old we might have a little empathy with them. Everything ages and lead is no exception.

What’s actually going on is oxidation of the lead.

Once lead is exposed to the elements it starts ‘taking on’ it’s environment and reacting to what’s in it. The surface of the lead interacts with oxygen and water in the air.

The Science of lead oxidation

Lead gives off electrons to oxygen, it’s state changes.

The change of state only happens on the surface of the lead. Firstly, the lead on the surface turns into ‘lead oxide’, the surface turns to a matt grey.

Water in the atmosphere will spot the lead and may produce a white powder, this is ‘basic lead carbonate’. This can run down onto the glass but can be wiped off without staining.

Basic lead carbonate turns to ‘normal lead sulphite’ then ‘normal lead sulphate’. This is when you get to the grey patina state, familiar on old churches and Victorian terrace houses where the glass such an age.

Lead patina

Leaded glass before aging

The patina on the lead protects the lead underneath. Think about a lead unit that was made up 150 years ago, the lead looks pretty much the same as the lead on an 85 year old 1930s leaded light because the state of the lead hasn’t changed for decades, the main body of the lead is protected now and will be unaffected.

So, the grey matt oxidised patina on lead is normal, inevitable and actually protects the lead. Don’t fight it, let it happen and enjoy it’s authentic qualities.

Speeding up the process of aging lead

Leaded glass personalised

When I make traditional stained glass for leaded glass windows I solder all the joints. The lead cames and soldered joints are all cleaned up and wiped down. We then treat the cames and solder with an acid to blacken the lead, take the shine out and speed the process of oxidation up.

The units look better than they would do shiny.

Stripping paint from glass & lead

Home strip paint stripper

For years now I’ve used Home Strip Paint & Varnish Remover to strip paint from glass and lead caming. It’s water based and has no toxins or fumes. Therefore, you can use it indoors without ventilation, unlike Nitromors which will have you high as a kite.

Just brush a little on the bits of paint on the glass or lead and rub in with a toothbrush, especially good for textured glass and around the soldered joints on the stained glass.

You will have the paint soft and removed within an hour when you can just wipe it off, I use a white scourer. Be careful not to let it drip down onto the door. When we’re refurbishing the glass we’ll take it out of the door or we’ll be stripping the door anyway so we don’t have this problem.

Don’t use an abrasive like wire wool or sand paper as you may scratch the soft old hand made stained glass.

On flat glass you can use a sharp Stanley knife blade for removing paint. On textured glass you can use the point of the blade but be careful not to damage the glass.

Cleaning leaded glass windows

This chemistry lesson is intended to help you with the cleaning process. Hopefully you will now know that taking the patina off the lead will only expose ‘fresh’ lead which will inevitably oxidise.

Elegant front door stained glass

Leaded lights, including the glass should simply be carefully cleaned with warm soapy water and dried off with a paper towel, lint free cloth or microfibre cloth. Don’t use an abrasive material like wire wool because you may scratch or dull old hand made stained glass.

Blackening leaded stained glass

When all of the dirt has been cleaned from the lead, around it and the glass is clean, rub some Black Grate Polish into the lead. I find using a nail brush is pretty good, it gets the black polish down the sides of the lead and evens the colour out very well. After seconds of scrubbing it around you’ll find that there’s little left on the glass. Buff the whole stained glass window down with a paper towel of microfibre cloth.

It does take a bit of time cleaning the glass but it’s well worth the effort. If you have six windows to clean up, don’t expect to have it done in an hour. Do the one in the door first, both sides. Put an hour aside for this at least. Do it properly and it’ll look lovely. Knowing how long it’s took and the effort you put in, you’ll be able to plan for the rest.

Lot’s of people read this blog. If it helped you please let me in the comments know how you got on.

If you have any questions please don’t hesitate to contact us or comment below and feel free to share this article.


Why not read…

Making leaded glass - Blog Cover

How we make our leaded glass

If you’re interested in how we make OUR leaded glass, which isn’t the same as traditional stained glass, have a read of this blog. 99% of the leaded glass you’ll see in the front doors on our website is made this way, and there are a few good reasons why. I’ll show you how our leaded glass differs from ‘traditional stained glass’ and how doing it this way benefits our clients.

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