I have 2 stained glass windows in my house and although they seem sturdy and in fair to good shape I've noticed the metal work (came?) is turning white and/or corroding in spots. A closer look revealed that there is a coating (lead solder?) which is in good shape at all joints but the rest of the frame seems to be bare metal. What would this metal frame normally be made of? It looks like it may be zinc? Can this be easily repaired (sanded and painted) or is lead solder somehow melted over entire frame?
If the metal is lead came and it's turning white it is "decaying". The white powder stuff is lead oxide. DO NOT SAND IT! It is VERY toxic. If this is your problem, there is no way to "fix" it, short of releading the window.
It probably is lead oxide as suggested. I wouldn't have used the word "decaying", although in the strictest sense of the word, it is decay. It's not like it's gonna fall apart like a rotten tree, though. Oxidation "is" decay, but not in the sense that your came is going to dissapear overnight.
That oxide is very toxic and you don't want to be inhaling any of it, or ingesting it in any way. Were it mine...I think I'd wash them down really well with soap and water and a very fine3M scratchy pad. (Don't use steel wool.) Gently. Very Gently. Once I got them clean and dry, I'd be tempted to liberally spray some Pledge (or similar) wax on the window and try to "seal" the lead. If you undertake this, use rubber gloves, a dust mask, use paper towels and throw them away. If you use any cotton towels, I'd toss them, too, along with the scratchy pad.
If you have small kids or pets that could touch the window, do this sooner rather than later to abate this. Don't let them lick the window, or touch it and then eat something. Lead is ingested into the body by inhalation of dust, and fumes, smoking while handling lead, and by eating while working with it. Just touching it isn't poisionous, unless it is ingested by eating or inhalation. Lead is not absorbed through the skin, according to the CDC.
It's a bit curious to me why the oxide is forming on the inside of the windows rather than the outside, as is usual. Nethertheless, you need to take some actions.
No, my wife says she only uses a clean cloth/towel to occasionally wipe them off (might wet it with water once in a great while). We do however run a humidifier in the winter (hot air heat) and the unit is in the same room as the windows. Could humidity cause this?
Hmm Been eyeing this thread and thought I would throw in a couple of cents worth.
In your original post you say the windows are in good shape except for the white residue. If its not broke, don't fix it. If you don't know precisely what you are doing with these windows, why make a bigger problem than what you have?
Keep doing what you are doing and they will be fine, the damp rag takes off the grime, the oxidation is from condensation and age, it happens. Don't lick them and they won't bother you. If they weaken, and the lead changes from its current state to something weaker, then be concerned. But unless you know what you are doing, especially if these are panels of historic significance, why run the risk of making a small problem a big one.
Somewhere down the road they may need to be releaded, but just because they have a little lead oxide does not require and "sanding" , ever. A srubby pad or sanding would just expose more lead to oxidize, in addition to what is already oxidized, why bother it if it isn't broke.
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