Backboard for Large Frame

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joh5nny
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Backboard for Large Frame

Post by joh5nny »

Hi all,

I've been asked to frame something that is 1680mm x 1430mm in size (approximately 66" x 56"). I've done a few large ones for this customer before, but none quite this big. Previously, I've just sandwiched the artwork between glass and a MDF backboard overlaid with a barrier board. I know that the artwork shouldn't be against the glass in an ideal world, but this is the methodology that was agreed with the customer for cost and aesthetic reasons. The methodology will be the same this time.

I'll be using acrylic rather than glass for this one because of the weight. I was thinking something like 4mm thick acrylic with a 6mm thick MDF backboard and the artwork sandwiched in between. The first problem, however, is that I can't get MDF wider than 4ft, so I need an alternative backboard that's big enough, gives me some rigidity, but isn't super heavy. Can anyone point me in the right direction for such a thing? Secondly, what thickness of acrylic do you think I can get away with for something framed in this way? I was thinking 4mm would be right, but maybe I'll get away with something thinner, or maybe you think I need something even more substantial?

Thanks
Not your average framer
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Re: Backboard for Large Frame

Post by Not your average framer »

I would go for joining two bits of MDF together with a sub-frame and reinforce the join between the two bits of MDF with a brace for the sub-frame. I tend to think that you pay much more for anything that is larger than normally stocked locally.

I try not to use Acrylic glazing, so I not the best person to ask, but I'm a bit wary about using 4mm Acrylic for something that large. I am thinking about how well the 4mm acrylic will be able to stay flat over such a large area.

Perhaps your supplier will be able to advise you.
Mark Lacey

“Life is short. Art long. Opportunity is fleeting. Experience treacherous. Judgement difficult.”
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prospero
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Re: Backboard for Large Frame

Post by prospero »

This is a similar size....

Start with a subframe made from pine cladding with the tongue slicced off.

Image

12mm thick and half-lapped and laminated. Very strong.

Image

Faced with 2.5 MDF panels corresponding to the crossbars. * Cat optional. :D

Image


Panels of foamcore tacked on with ds tape.

Image

The 'art' (a big map) was in direct contact with a sheet of 3mm Polycarbonate. If you seal the edges then the vacuum effect
keeps the glazing from bowing.


Image


The subframe was cut with a little cavity on the inside of the top rail and wall cleats made for them to perch on. Very stable.
Even with plastic glazing it was mighty heavy. :P Have Fun. :ninja:
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Not your average framer
Posts: 11014
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Location: Devon, U.K.
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Interests: Lost causes, saving and restoring old things, learning something every day
Location: Glorious Devon

Re: Backboard for Large Frame

Post by Not your average framer »

Very interesting and useful to know that 2.5mm MDF is sufficient when supported with foamboard. I did not realise that the 3mm acrylic could be kept flat by sealing the edges and using the vacuum effect. I may decide to adapt some of these ideas in the future for my own use.

Thanks Peter, for your very clear explanation.

I must admit that I'm still not much of a fan of acrylic glazing, I don't like the static attraction and how it attracts dust and I'm always worried about the possibility of it getting scratched. I know it's lighter in terms of weight, but for me it's still second best to using glass.

I buy 6mm MDF cut to size from my local hardware shop and for me this can interupt my work flow while I wait for the hardware shop to find the time to get round to cutting it for me. Perhaps I can save time by doing something similar by backing my normal backing board with D/S tape and foam board.

My new shop is smaller than the old one, further from the hardware shop, I need to find ways of being more efficient in this smaller space and I risk missing customers while going to and from the hardware shop.
Mark Lacey

“Life is short. Art long. Opportunity is fleeting. Experience treacherous. Judgement difficult.”
― Geoffrey Chaucer
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David McCormack
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Re: Backboard for Large Frame

Post by David McCormack »

I know you say you have used glass before for this customer, but you will find that acrylic glazing is a much better choice when it is in direct contact with the art. It's all to do with temperature changes, humidity and dew point. Glass is more likely to produce condensation than acrylic and when that happens the art and glass can stick together.

I have a large framed OS map, in my kitchen at home, that is in contact with the acrylic glazing and so far it has not scratched, despite the constant finger pointing whilst planning walks! Dust doesn't seem to be a problem either so far!

Before glazing a frame with acrylic, and before removing the protective film on both sides, wipe the whole sheet and edges with a clean damp cloth and then a dry one. I find this helps with reducing static and make sure your work area is as clean as possible.

Also FYI, this place sells 8x5ft sheets of 6mm MDF but I would go with the advice above about joining smaller sheets and using sub-frames. Good luck with such a big frame :D
"You know, there's a right and wrong way to do everything!"
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