Black spot on mirrors

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Black spot on mirrors

by Antoinette
(Ireland)

I have been making mirrors for a good few years but every now and then black spot appears after a while on some not all of the mirrors. I have been using nail varnish as a sealant, I was just wondering if you could tell me what type to use. I have found CRL Gunther Seal-Kwik Mirror Edge Sealer on the internet but unfortunately I cannot get it here in Ireland.
Many thanks for your great site.
Regards,
Antoinette

Answer

I Googled mirror edge sealants and came up with This Page of available sealants. Perhaps you can find one of them in Ireland. Whatever you use, make sure you seal on to the back edge as well. When you cut mirror, minute chips of the backing come off when you break out the pieces and give entry to the contaminates that cause the black rot. Sealing along the back will cover those chips. I actually seal the entire back of mirror glass.

If you can't find any of the sealants, try a polyurethane spray.

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Black spot on mirrors

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Aug 22, 2011

Shellac NEW
by: Karin

I use a cheap foam brush to put 3 coats of shellac on the back of cut mirrored pieces before I foil and solder them. Sometimes there's a wee bit of bubbling noticeable in the top coat of the shellac if I'm working slowly, but I try to make a point of wiping the flux off off as soon as I'm done the soldering so that it doesn't stay on the glass long enough to eat through the other protective layers. I've never had a problem with black spots yet, knock on wood!

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Black spot on mirrors

Comments for Black spot on mirrors

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Black spot on mirrors