Backboard pressure

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Ed209
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Backboard pressure

Post by Ed209 »

When you fix your backboard should you press down quite hard with the Fletcher point gun like I have been doing or just gently?
I have just framed a old family photo of a child that was taken in the 1930s and is on a card but there are gaps between the picture and the double mount, the card didn't seem excessively bent but I wonder if I have applied too much pressure particularly in the centres of the moulding
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prospero
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Re: Backboard pressure

Post by prospero »

First of all you don't need excessive pressure on the points. As long as the back doesn't move about it's OK.

What's happening is the back is bowing out. This could be because you are pushing too hard on the points. :P

What backing board have you used?
Boards tend to have a 'bias'. That is, a natural curve. If this is so then flipping the backboard over might help.

Another sneaky trick in cases like this is to cut a piece of mountboard just a tad larger than the mount window and
tape it to the back of the undermount, (You have got an undermount I hope....) in register with the mount window.
snipping the corners off helps it sit better. Then the backboard applies a tiny amount of 'push' in the middle and takes
up any slack.
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Re: Backboard pressure

Post by Jayvee »

I’ve been having this issue too - using Artback Aqua. The board tends to have a bias, but - sometimes it bows in and then out in the same sheet.

I sometimes use foam board as well as artback - sometimes this works...although I do like prosperos tip a might have to use that soon!!! :)

Probably going to be looking at changing my backing board - was looking at Lions kraft lined foam board....anyone have any experience with it? Or perhaps another type of board that’s pretty good? :)

:rock:
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IFGL
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Re: Backboard pressure

Post by IFGL »

Hey ed is that a crossbow you have there in your avatar and if it is are you using it to shoot "nails" into the frame to hold the backings in, if this is as I suspect what's happening then I think we may have stumbled upon your problem!
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Re: Backboard pressure

Post by Not your average framer »

Backing boards are often bowed, it's just one of those things. In the days when most people were using MDF, I always used to look and see if the board was bowed one way, or another. The place where I first worked as a framer bought huge quantities of MDF and when you saw them in a stack, the individual boards did not stack nice and evenly, because they were all wavy. The modern non-MDF boards don't tend to be completely flat either.

Some types of boards are less of a problem than others, but there are ways of working to avoid some of these problems. I don't suppose that we all tackle these things in exactly the same way, so there will be differences. I have to be particularly careful, because half the houses around me don't have a damp course and it's a wet part of the country. Damp and backing boards not staying flat seem to demonstrate a connection.

Mountboard is a lot more likely to remain flat than many modern backing boards. I've tried them all and some backing boards are a lot better than others. My favorite was Conservatek which is no longer available, but I do prefer backing boards with a solid core. There is a lot to be said for using an undermount behind the artwork, not only because it is good practice, but not being made of different layers of materials mountboard usually stays flat.

Sometimes the artwork does not want to stay flat and there are times when you have to resort to other methods of keeping things flat and the artwork nicely seated flush with the window mount. Variations on the pedestal mount can help sometimes and there are other techniques used by different framers. However, I do have to say that I miss some makes of backing board which really did stay flat and are no longer available.

I used to like Britiania's 5mm thick CombCore, but that's long gone now. It was very stiff and great as a backing board for deep box frames, where the backing board spanned a large open space without any other means of support. This might sound crazy, but I buy Simons BACK-01 which is a cheap non waterproof corrigated backing board and glue two sheets together with the flutes in one board at 90 degrees to the flutes in the other board.

You need to do this in a press and any bow in one board needs to oppose the bow in the other, but it does produce a very flat and stiff board, if you don't mind all the etra fuss to do this. I be interested to see what comes out of discussing this subject, which I think is probably something that most of us have to contend with at various times trying to get the right result. I think that there's still a market for Conservatek, or CombCre!
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prospero
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Re: Backboard pressure

Post by prospero »

I've said this before and I'll say it again. :lol:

I use 2.5mm MDF on everything.(2mm is not good for anything bigger than 8x10")
I've tried card backing boards and while it appears to do the job it has many drawbacks.....

The solid stuff is strong but not nearly as rigid as MDF. It's also very hygroscopic and goes mental near the slightest bit of damp.

As for the corrugated stuff, you might as well use cornflake packets. :P

Foamcore is better, but very susceptible to damage. Also expensive.

I think a lot of the prejudice about MDF stems from a health report from some years back warning of the dangers of inhaling
the dust. The report was a bit misleading. It was aimed mainly at workers who are sawing big slabs of it all day. Inhaling any
dust on a regular basis is not a good thing. And besides, MDF used in framing generally is not sawn. But the myth persists.

MDF does absorb moisture. Not nearly to the extent of soft card. As a failsafe I always impose a barrier of plastic film (the wrapping stuff)
between art and back. Takes seconds to cut and the film is cheap.
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Ed209
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Re: Backboard pressure

Post by Ed209 »

What size sheet of 2,5 MDF do you get? Wessex do four different sizes bit much for my non mathematical brain to work out the best value
I have a Fletcher 3100 with Hardboard cutter attachment so no problem cutting
I always was biased towards MDF but was dissuaded by others probably based on the misleading info you mentioned
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prospero
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Re: Backboard pressure

Post by prospero »

4'x3' is my usual size. Now and then I have to get some 6'x4'. As far as wastage goes, the bigger the sheet, the less waste.
But the larger sheets are a tad unwieldy and a problem to store, so it's a toss-up. :wink:
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Ed209
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Re: Backboard pressure

Post by Ed209 »

The back board I have tried so far is Corri-Cor Mark 3 which I was not that impressed with also I have NuBord® which is a greyboard with a good quality kraft paper on both sides. It is an excellent rigid alternative to MDF (product description) It comes in two thicknesses, 2.3mm and 1.79mm which I quite like.
will try real 2.5mm MDF next

With regard to using a under mount I have so far found that a lot of the time it leaves insufficient depth to get the backboard in as well, Especially with a double mount (that I do a lot of) So I have been using a 425 microns barrier board instead. I like the idea of the undermount method and adopt it where possible.

Another problem I have come across lately is the Thunder bugs/Thrips getting in to the pictures, Have had several enquires about re mounting /cleaning etc,and obviously preventing it happening again, So any tips on that please, So far I have seen some metallic tape to seal glass to undermount

Have just dis assembled the problem picture in my original post and the card the image is on is is quite thick and very curved backwards on the outer edges and requires considerable hand pressure to flatten it out to lose the gap from the mount. so not a easy fix for this one. the card is over eighty years old so getting quite brittle So live with it or scan it, Its a photo of my wife's mother and shes happy with it!
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