The Framers Forum

So I did this piece about 6 weeks ago. It was as you'd expect, perfect, when it left here. Hung straight on the wall. Centrally heated stone cottage outside wall, "near" but no above a radiator. It was brought back in this week and the corri con backing had completely ballooned outwards, pulling the undermount and work out as well as if it had be drawn out to the cold wall. (Not a damp house apparently.)
I opened it up to check that it wasn't too tight in the frame, but plenty of room for expansion under normal circumstances. I flipped the backing over and closed it back up. With the now extremely concave backing board, this pushed everything back into it's place. All fine. The customer's entire house is "filled with pictures and nothing like this has ever happened before".
I received this photo this morning, to show that the same has happened again. we had discussed how all of her other framed pieces, done years ago have hardboard backing, so we discussed that if this happens again, I would swap out the corricon for hardboard. I'm now wondering whether the Correx fluted plastic backing from Lion's might be a better option considering what has gone before...
Any thoughts?

It wouldn't hurt.

The big however, is that air currents are not limited to a planer barrier and will travel where there is the least resistance. I.E. the atmosphere around the entire framed item is affected from all directions. Obviously, mostly from the side against the wall.

So, let's assume that the wall isn't damp, then it's the temperature fluctuation around the frame versus the temperature of the cold stone wall which is causing the reaction? This time the customer noticed that it had happened overnight, since she rehung it yesterday afternoon.

Correx may help. especially two pieces bonded together with the flutes running perpendicular to each other, also, if you sealed the glass "sandwich" - don't this time. Maybe add extra deep custom made wall spacers made from acrylic or something, instead of the usual bumpons. Foil frame sealing tape might help too.

After that I'd politely explain that's all I'd be doing for free (assumimg you are making these changes FOC) and I'd also request, seeing as this time it happened overnight, that the customer leaves or hangs the frame somewhere else, on/against an inner wall nowhere near a heat source for example, or even with you for a week or so (in fact you could do it same day and wait a week or more to tell them it's done!) - then if it doesn't warp, try again and if same happens, lesson learned - don't hang stuff there any more!

A moisture tester may be a good investment too, not for their walls (but maybe) but for the frame (or any future ones) coming back, in case it has moisture from their home left in it. If it did you could show them that compared to a piece of your own.

You can't be expected to alter nature so you should also explain you cannot guarantee any attempted remedial action.

@john so why not seal the package?
Yes I have a moisture meter, I'll check it when it comes in on Monday. (I did offer to drop it back last time and have a look at the hanging place, but she was a bit defensive).
Incidentally when she brought it back in on Monday with a completely warped backboard, I left it overnight face down on the bench and by the morning it was almost completely back to flat.
I'm thinking hardboard backing (as that's what she wants, with correx last before sealing.

Justintime wrote: Thu 16 May, 2024 1:51 pm @john so why not seal the package

Well, although this may be OK in normal conditions then for these conditions, the same reason as you wouidn't tape a print all around, to allow movement, If the boards are going to move, they can only do that where there is no tape.

Maybe this is the only thing they have which has the glass sandwich taped.

I'd have it in writimg that the hardboard wasn't my idea.

JKX wrote: Thu 16 May, 2024 2:12 pm Maybe this is the only thing they have which has the glass sandwich taped.

Interesting point.

"Incidentally when she brought it back in on Monday with a completely warped backboard, I left it overnight face down on the bench and by the morning it was almost completely back to flat."

One thing to remember with an exterior stone or masonry wall, they are porous to moisture. They are not vapor proof.

You proved it by leaving the frame package overnight on your workbench.

@JFeig So if I'd just used a backing board with a waterproof backing it would have been better. I think I'll go with Correx this time. And maybe do an acrylic sealant over the gummed backing tape.

It will be interesting to hear how that all works out.
I'm sure you'll cope magnificently.

When you mentioned that the customer has had all her pictures backed with hardboard, I decided to look up the subject a bit more.

If you mention 'hardboard' to most people, they think of 2mm MDF board. Conservation conscious framers don't like using that stuff as the MDF is manufactured by compressing wood pulp using a urea binder which may leach out into the frame package.

Traditional hardboard is made from the same wood fibres but by the use of steam and pressure, the binder is the natural resource of the wood itself.
So, a sheet of real hardboard, although man made, is identical in substance to a plank of wood.

If you can get it, traditional hardboard would give a much more substantial backing to a frame, certainly compared to a lightweight corri board.
Others might take a different view.

Wessex Pictures have it on their web-site, available - whilst stocks last!

This is not entirely unusual I would suggest to the customer to lift if off the wall if possible, even though this may not stop the problem it may help.

Water resistant boards will help and joining two together will make a much more rigid backing board as John explained. a plastic spacer or even a rubber doorstop cut to height and screwed on will give greater airspace as suggested. I have in some cases where I know its going to go in a problem area (always ask the customer where it is going to hang, so you can add in barriers) addeded ribs/tin foil to the back of the frame inside and outside. On the outside taped on with rebate sealing tape or plumbers 50mm wide foil tape.

So what's the best glue to bond two sheets of Correx??

I used to use one we sold by "pinflair" but remember thinking it would be rather expensive if we didn't buy it for resale!

I'd make a grid of beads and spread them with a spatula then leave under weight.

Read the last two posts in this thread.

https://www.thegrumble.com/threads/seal ... st-1057856


.

Interesting. Any reason not to use industrial super glue?

I don’t see why not, it’s between the two sheets then there’s an undermount.

Thanks, I'll do a test piece first, as I just found this :
"Polypropylene plastic, mainly used in automotive and textile industries, does not glue well with CA glue. This is mostly because of its semi-crystalline nature and its high chemical resistance."

Test results are in! Drum roll...
No. Correx to correx, no bond. 180 grit sanded and wiped down with alcohol gave a bond at least but not strong enough.
I'll try hot glue next.

That's the first thing that comes up when you google "bonding correx to correx"!


https://www.gluegunsdirect.com/2014/08/ ... ng%20needs.



..

Yup hotglue works, it does pull apart with force. I'm sure that Tecbond would be the way to go. Who knew there were so many types of glue stick??