You must use the proper glue for mirrors or the glue will eat the silver off the back.

Call your local glass shop and purchase the right glue from them per their advise. You shouldn't need to rabbet the trim, bumping the trim up to the mirror will leave the beveled edge intact where you can see it as you have planned. Glue the mirror to the ply, mount the ply to the wall, stain or paint the trim and install, touching up the trim after it is in place.

Thanks for the help. IÂm not clear on why I would need to raise the mirror up? To make the bevel more visible? I was not planning on using a thick molding. I have not chosen it yet, but was planning on something that would taper from a thicker profile at the outside edge to thinner at the inside, by the bevel. (assuming I can find something like that)

sierra east, I want to make sure I have this correct: you mean mount the plywood with the mirror to the wall by screwing through the exposed edges of the ply to the studs? Then mounting the trim over the mounting holes? I hesitate to do it so permanently: what if I want to paint or rearrange the furniture?

My advise would be permanent, so i guess that wont work for you. Make sure the way you hang it will support the weight!

The way you have planned sounds like you will still have the plywood edge grain exposed at the sides. If you use 3/4" ply, you could trim around the perimeter with 3/4" stop material and trim flush to that or trim past it a tad.

I recently did a project like this, and found "Mirror Mastic" at my local Home Depot for a reasonable price (cheaper than the local glass shop).

I have used liquid nail to hold mirrors before and have never had a problem. Once that stuff dries it won't let go.

They sell Liquid nails for mirrors, take a look.

The others are right, though you need to be careful because a lot of adhesives will attact the silvering (ok, these days it's aluminuming) and you may want to remove it one day - use the special stuff, but most framed mirrors don't use adhesive at all, they're held in place with brads or, preferably, beading.

My wife and I obtained some doors that were intended to be glazed or perhaps have a panel in them; ie it's the outer part of the door with an open centre, and we've been talking about making it into some sort of decorative mirror. I suspect buying a made one would be cheaper, but we're thinking of doing something nifty and personal with it. I'd be figuring on beading holding the mirror in, it'll be backless.

In the op's situation glue is a good idea, as for the rebate for the edges of the mirror, if you have a friend with a table saw or even a hand saw with a fence, it's very easy to make a rebate/notch that will help hold the mirror in place, even if it's 1/8" - but your gluing thing will probably work but I'd be very careful...you'll probably want to screw the frame to the wall to be safe.

How wide is the bevel on the mirror? If the mirror is square you can mount the mirror on a substrate that is slightly larger - say a quarter inch all around. Most frames have a lip of 1/4 to 1/2 so it'll cover the substrate and the edge of the mirror. The frame should have wire in the center to "pull" the top and bottom to prevent it from bowing. Depending on the thickness (weight) of your mirror, you can probably get away with mounting it on masonite. Hope this helps.

As above, use adhesive recommended specifically for mirrors.

While I might have gotten a bad batch, a mirror I glued to plywood (very similar situation to the OP) failed after about 10 years. So I'd recommend a mechanical attachment as well, such as edge moulding or screws (with decorative caps) through the mirror and ply.