A bit of framing physics advice, please...

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cleaver
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A bit of framing physics advice, please...

Post by cleaver »

Hi All,

Got a question regarding the job I put up on the Members' thread.

Basically, it's a large-ish frame, with glass, and I want to get some advice/reassurance, please.

The overall frame size will be 100cm x 70cm (portrait format).

The poster is already stuck down to a flimsy bit of (flooring?) hardboard, which I will beef up with another bit of 2mm MDF - stuck to the existing hardboard (as the poster has been supplied stuck down, and thankfully I am not being asked to remove it from the hardboard). So I'll PVA glue 2mm MDf to that that existing hardboard.

Big question is: how thick should the moulding be, so it supports the weight and doesn't distort/flex? BTW, I'm going with 2mm float glass, as I believe it doesn't quite warrant 3mm (please correct me if I'm wrong there).

I was thinking of a moulding (flat profile, as that's what been asked for) from Wessex, reference M04391. It is 1.5 inches.

Do you think this is beefy enough? And, out of interest, what's the minimum size (wood) moulding you'd use? I know that if it's really thin, it'd have to be metal moulding, but the customer wants wood.

I just don't want it flexing and breaking the glass, or any other disasters!

Ta
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Re: A bit of framing physics advice, please...

Post by Not your average framer »

2mm MDF is not going to add any significant improvement in either rigidity, or thickness. Not only that , but any stresses set up between the existing hardboard backing and MDF glued to the reverse face of the existing backing may far to easily result in bowing or flatness problems. How flat is the existing hardboard backing?

If the existing hardboard backing is reasonably flat, I would probably leave well alone and use an additional 6mm MDF backing board behind this, but I would not be trying to glue the two board together. It would not normally be considered a good choice to allow the poster to be in contact with the glass, so some sort of spacing around the edges to maintain separation between the poster and the glass should be considered, to prevent unintended adhesion between the glass and the print.

I'm not aware what the specified moulding is like, therefore if this moulding is not rigid enough it may be necessary to consider a sub frame inside the reverse of the frame. With this size of frame you could be looking at something that is likely to be getting a bit heavy as a finished job. It's not always easy to advise about something like this without being able to see it for one's self.

In bygone days, many items iike this were framed in fairly flimsey frames and no effort was taken to address long tern flatness and as a rule nobody was much concerned. Customers still bring in large frames using flimsey hardboard backs from a very long time ago and most of them are still in reasonable condition for their age. It's not uncommon for customers who are not wanting to spend much to keep the original backs.

If you just need to have the 2mm MDF as an additional backing board to make the rear of the frame look neat and tidy, I would not be thinking of gluing this to the rear of the hardboard backing.
Mark Lacey

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cleaver
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Re: A bit of framing physics advice, please...

Post by cleaver »

Thanks, Mark.

You are bang on: it is an 'I don't want to spend much' job. It's a mass-produced poster, so I totally understand that thinking. It's been stuck down firmly straight onto the hardboard, so I am glad not to be involved in reversing that.

The hardboard is very thin, and bends under its own weight when free from the frame. Do you think I should go for 3mm glass, and leave the flimsy backboard as is? Would 3mm glass 'support' the whole thing?

Or should I recommend acrylic (but I guess that'll blow the 'keep the cost down' bit)? I'm sure they won't want to pay for a sub-frame.

BTW, there is a mount.

Ta :)
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Re: A bit of framing physics advice, please...

Post by Justintime »

3mm glass will just add more weight.
A well glued and joined frame of 1.5" sounds fine.
Sandwich with the glass, add a backboard and finish, job done. Allow for 2 points of hanging , when putting the cord on, this will reduce the stress on the frame from hanging.
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cleaver
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Re: A bit of framing physics advice, please...

Post by cleaver »

Thanks, Justin.

So you wouldn't beef up the ultra-flimsy (wappy!) hardboard with anything? I have some Artbak, but would that do any good or just add bulk?

BTW all, I know this piece isn't an outlandish size; I'm just being paranoid, as per usual :lol: Still, better to ask people who know better, than try to be 'smart'.

Chairs,

P. :)
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Re: A bit of framing physics advice, please...

Post by prospero »

As mentioned, trying to beef-up the back will just add weight. I should ideally have a back as the board it is mounted on
it considered part of the 'art' and should be enclosed. The frame sounds adequate. Often with skinny frames on biggish picture
it's the hangings that stress the frame and cause the joins to fail. One way is to rivet (double?) d-rings to the backing board which
lets the back take the weight. To do this you would have to use at least 2.5 MDF.

The glass shouldn't be in contact, although as it's stuck down it won't wrinkle. If it's kept in a stable environment it will probably
be OK. Not the ideal situation. Spacers under the rebate would help.
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Re: A bit of framing physics advice, please...

Post by Justintime »

As prospero said, it requires a backboard, as does all work. Heavier backboard isn't going to stop the frame sagging at the bottom, if it wants too, but its unlikely to.
If you cord it leaving enough for 2 fixings, this reduces the weight/stress on each d ring.
I measure in 10cm by 10 cm from the inside corner of the top of the frame, mark 2 X's on the backboard, tie the cord to reach those two points and tell the customer that these are the hanging points, stress that it requires two points. Then its on their shoulders.
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Re: A bit of framing physics advice, please...

Post by Steve N »

I think you only need to use just 2mm MDF or whatever backing you normally use, depends on the moulding, as long as it's deep enough to take the glass, artwork and the backing board you should be okay, if its a thin moulding, then d-ring and rivet the backing , 1/3 down from the top and about 4cm in from the sides, on a Portrait frame I wouldn't be too anal about hanging from two hooks, I only do it on Landscape ones, I have some printed labels with it on, showing the cord going over two hooks and just makr the back as Justintime does, just point it out to the customer

Arkbak will do fine, you can rivet your d-ring in that no problem
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Re: A bit of framing physics advice, please...

Post by Not your average framer »

A lot of my customers for jobs like that are not wanting much more than a modern looking replacement for a tired old looking frame and it's fairly typical that your average customer likes to see a poster framed in a narrow frame. If there's not much money on the table, the frame with quite often be Rose & Hollis A113 (oak) frame moulding which is not only nice and narrow, but it surprisingly still and the old backing board would be left as is with a solid craft board behind it to make a nice neat looking finish on the back.

It works out very affordable, looks great and often results in some follow on business as well. Many jobs like this are of no special importance to the customer and just need a bit of tidying up. BTW, 2mm float glass is fine for something this size. Keep it quick, simple and easy.
Mark Lacey

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cleaver
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Re: A bit of framing physics advice, please...

Post by cleaver »

Many thanks all :clap:
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