Framing a heavy mirror

[Starboard]

Hi, Framers,


Thanks to friendly advice on this forum, my first framing efforts (a large tray frame for a canvas) were really rewarding.

So I am now commissioned by my best, most demanding and only customer (my wife) to make a quite large-ish mirror: glass size would be 1,000 x 1,000mm.

Quick look up on the net gives average weight for MDF 4mm backing at 3kg/sqm and glass at 10kg /sqm for 4mm thick mirror, unsurprisingly 15kg/sqm for 6mm.

Depending on backing/mirror thickness, this would be between 13 and 20kg excluding moulding.

So, there is a deluge of questions such as:

* What is, in your experience, the best building method? I was thinking of glueing the mirror to a backing (MDF or other) for safety, and also using the backing for fixing in order not to stress the frame, but that may no be the best option.
* Would you go for 4 or 6mm? My guess is, 4mm + glued to backing is probably enough, this is nit a commercial application
* What material / thickness would be good for the backing?
* Do you leave some wiggle room between the mirror and backing and the frame ? Are there any expansion issues to take into account?
* What type of fixings would you recommend?

I found this type of system from a commercial supplier, but I am not sure about the D ring fixings on the frame

Thanks for any pointers. I could always "give it a go", but usually, I end up finding there was one or several "tried and tested ways" of doing things. Ask people who know!

[pramsay13]

I think you are maybe overthinking things.
At that size I would be happy with 2mm mirror and backing.
It would probably be easier just making it 4' x 3' which is the standard sheet size, otherwise you will have to order an oversized sheet and then cut down to size. If it has to be square make it 915mm x 915mm.
Then just frame as normal and add a wire and hang on hooks. If you're worried about the weight you could use cleats.

[JKX]

I don’t think you can buy 2mm mirror glass - certainly not from Wessex or Centrado anyway; they start at 3mm and it’s already safety-backed. The safety backing is only a polypropylene film but maybe that and the silvering makes it 3mm minimum?

So no need to stick mirror to backing - if it does break that’s two things to replace!

2mm glass for a mounted thing that size is OK - even if borderline, but in that case there would be an air gap between glass and artwork/backings. So 3mm against a backing would be fine.

I’ve had plenty of mirrors in for repair and have seen a lot of overkill, like being stuck in to the rebate with mastic, then the backing board being held in with quadrant moulding nailed and glued to the rebate, huge screw rings and wire like a coat hanger, etc.

Here’s one I used to have, solid oak frame and backing - held in with turn buttons, albeit pretty heavy duty ones.

I would just use framers points and foil tape. I’d make sure the rebate was filled to put the backing as close to the wall as possible though. If weight is an issue use correx. Two pieces bonded together with the flutes going perpendicular makes for a very strong but lightweight board.

Mirrors are best flush to the wall, so maybe not wire. Z bars are good and could go top and bottom, then there are strap hangers etc - mine as you can see used keyhole hangers which were fine but take very accurate positioning of wall fixings.

I