How can I seal back of a mirror

longwalks1

I’ve got I’ve got 2 mirrors (framed) and the back of them is the kind of board you get on the back of cheap chest of drawers, maybe like a fibreboard.  I want to use them outside, what’s best to treat the backing so it doesn’t turn to mush after the first drop of rain? 

Would a waterproof paint/ducksback be enough, or would they need actually covering and sealing?

thank you in advance 

grumbler

longwalks1 said:

Would a waterproof paint/ducksback be enough, 
 

No, I don't think so. You need to replace this stuff with something really waterporoof and, what's more difficult, to seal the edges to prevent corrosion of the mirror layer at the back.

ThisIsWeird

Any chance of a pic, Long walks?

There's a few issues here. One is the, presumably, hardboard/MDF backing board, which will turn to mush pretty much regardless of what you do to it. So the best solution is to remove it. I suspect it's there as a protector/buffer for the glass, or to contain it should it break. Once mounted - especially outside - it should serve little purpose.

The next issue is this 'frame'. What's it made from, and how is it finished. Again, almost certainly it won't cope with much outdoor life. It'll likely need preserving and/or sealing to make it last outside.

And the final issue is the mirror. Depending on its quality, it might do ok, or may begin to suffer quite quickly - by that mean moisture creeping in the edges, pock-marking the back, etc.it might be pretty resilient, and could survive ok, but how to tell? No idea.

So, if I were looking to use an 'indoor' mirror outside, I'd dismantle it, discard all hardboard or MDF type materials, preserve and then protect the frame on all sides and edges using a proper outdoor product like Zinsser, and also 'paint' the whole back and edges of the mirror itself in ditto. Then reassemble.

You might get 5 years out of it...

twopenny

You would need to seal around the front of the frame and the back as well as preserving the frame.
You then need to be able to get it out when it needs replacing because damp will affect the mirror coating eventually.

You may find the glass cracks at high or low temperatures.
A normal glazier company can cut bathroom mirror glass to fit. Shouldn't cost much and won't be susceptible to damp.