The Framers Forum

I've got a large artwork to float mount in a frame with fillets. The overall size of the mountboard on which the artworks are floated will be 1265mm x 930mm. I need to use non-reflective glass and there's a huge difference in price between 2mm and 3mm glass. As the glass will be unsupported in the middle, my question is whether 2mm thick glass can be used, or whether it will have to be 3mm thick? Any views on this would be appreciated

I've always understood that 2mm plain float glass is only consider suitable for sizes upto 1 metre square glass size. Normal diffused reflection (non reflective glass) tends to fuzz the image as it is moved further away from the object, or artwork, so normal basic non reflective glass would not normally be used in a box frame. Anti-reflectice glass, which feature an anti-reflective optical coating would therefore be a better choice for a box frame, but there is an increased cost penality for anti-reflective glass.

I wouldn’t consider 2mm glass of any type - same as Mark, our rule of thumb for 2mm glass is up to 1 sq metre. Don’t underestimate the extra weight of 3mm glass. Again, we stay away from any products that use diffused surfaces to control reflections/glare

Wessex and Centrado have a variety of acrylic options, some at prices that may make your (and your customers) eyes water. Lion have a new product (Moth Eye) but I think the sheet size is too small for your piece.

Moth Eye would have been great for you as it's 3mm as standard. Is there any way that you can sell the customer on less border around the works to bring it back to standard size? At this size you'll need jumbo mount, jumbo glazing, jumbo backing....that's a lot of jumbo!! As has been mentioned, 3mm glazing at this size will tip the scales too. The last piece I did around this size, the glazing alone added approx 6kgs to the overall 16kgs weight of the piece (acrylic would have been approx half that weight but £££). Some correctly rated strap hangers or other will also be required.

It’s a shame nobody, supplier or maybe the guild or any other trade body, does not have a list of max sizes per thickness of glass - or acrylic come to that. Although acrylic is safe, it still has to be thick enough to not flex too much.

My SOPs were one sq m for 2mm glass - after that it was a case of just what feels safe for glass and what stays rigid or almost, for acrylic.

I’d say that if two people standing each side of a piece of glass on its long sides, picked it up horizontally from the centre with one hand each, if it flexed so much they knew it was going to break - it’s too thin, same exercise with acrylic, if it bends too much it’s too thin.

Here’s a 1mx1m piece of 3mm Uv acrylic with rebate spacers - it looks awful and was threatening to pop out of the frame. I replaced it with museum glass in the end but even though that’s actually 2.5 mm - I still wasn’t too happy!
(Lyrics to Pink Floyd’s ‘wish you were’ here BTW)

So your frame is too big for 2mm glass or 3mm acrylic IMO, and NR glass, which I hate on anything anyway - is terrible when spaced more than one or two mm away from artwork.

If the frame is hefty and you hsve assistance, 3mm glass may be acceptable - but not for me. I’d be looking at 5mm acrylic at least