MDF or Ply for the back of a heavy picture frame?

[el_Pedr0]

I'm making a glorified world map pin board and putting it into a frame to hang on the wall as a pseudo artwork. I need a back that will stay flat.

The overall size will be around 1600mm x 1200mm

The pin board itself is Sundeala K which is reasonably heavy and is very 'saggy' - i.e. it will bow out of plane. And as this is a pin board, it won't have glass to keep it flat. So I need a backing board that will hold the pinboard nice and flat from behind.

What would be the best material for the backing board to keep the pinboard (and therefore world map picture) totally flat, while keeping being mindful of not adding unessecary weight?

Ply? MDF? 6, 9, 12 mm?

 

[sammy.se]

Ply is lighter, and 9mm should be plenty good and flat

 

[el_Pedr0]

Ooh - Or what about 11mm OSB? I've got a spare sheet hanging around here. Or is that more liable to deform over time?

 

[mathias]

Masonite?

... and why is there so little talk about it? It can be made without additives or if some has been added it is not even close to what you find in mdf, plywood etc...
A lot of energy is used to make it, so that is negative but everything else is environment good I believe.

 

[Dee J]

Masonite?

... and why is there so little talk about it? It can be made without additives or if some has been added it is not even close to what you find in mdf, plywood etc...
A lot of energy is used to make it, so that is negative but everything else is environment good I believe.

Not familiar with the term Masonite - had to Google it. Seems to be what I'd know as hardboard. Think it got a bad reputation in the 60s home 'modernisation' business-but still used for furniture backs etc. Some of the cheaper hardboard available in DIY store tends to warp too, so needs a very stable support.

 

[Tris]

Would it work if you were to deepen the frame slightly and add supporting strips at intervals? Bit like drawer muntins, and saves the weight of a whole board

 

[rajsol3000]

I'm making a glorified world map pin board and putting it into a frame to hang on the wall as a pseudo artwork. I need a back that will stay flat.

The overall size will be around 1600mm x 1200mm

The pin board itself is Sundeala K which is reasonably heavy and is very 'saggy' - i.e. it will bow out of plane. And as this is a pin board, it won't have glass to keep it flat. So I need a backing board that will hold the pinboard nice and flat from behind.

What would be the best material for the backing board to keep the pinboard (and therefore world map picture) totally flat, while keeping being mindful of not adding unessecary weight?

Ply? MDF? 6, 9, 12 mm?

12 mm osb is the way to go pedro, 12mm ply is rarely flat unless you are spending big bucks on the really good stuff, 11mm MDF will change shape over time unless again you are spending big money on the really good stuff. The most cost effective way forward for you would be either 12mm osb which is very solid and stable as it has large peices of crossing grains and lots of glue in it or chip board for a similar reason.
Good luck

 

[mathias]

Masonite is wood only (wood fibres and lignin) and is a type of hardboard.

Apparently hardboard could also be made from paper in the UK.

I'd say Masonite is underrated and could in many situations replace OSB, MDF and even plywood. As it is wood only it is easy to recycle so maybe even though using a lot of energy to make, at the end of the lifecycle it has not had a big impact on the earth?

I have the book "Känsla för masonit" that talks about the short history of masonit in Sweden (yes, in swedish...), how and when it was/is used.

 

[el_Pedr0]

12mm ply is rarely flat unless you are spending big bucks on the really good stuff, 11mm MDF will change shape over time unless again you are spending big money on the really good stuff.

Yes - this has been my experience as a layperson. But that's buying from the diy sheds or the timber merchant.

Using Birch ply earlier this year for some furniture making was a revelation in terms of flatness and rigidity , but also price

Good to know that osb isn't as liable to distort as much over time. I think I'll use that on this occassion because I have an offcut lying around.

Would it work if you were to deepen the frame slightly and add supporting strips at intervals? Bit like drawer muntins, and saves the weight of a whole board

Good idea, and certainly possible in my situation. If I didn't have the OSB lying around getting in the way, then this would probably be the way I'd have gone to reinforce some ply.

Thanks all for entertaining the basic questions like this. I'm developing the skills, but the experience takes a lot longer, so it's really useful being able to tap this pool.

 

[recipio]

As I understand it Masonite is an American brand of hardboard. I don't think I've ever seen it for sale. With those dimensions you certainly need a stiff panel board. I used to use 5 mm oil impregnated hardboard which artists use for painting. It's very stable stuff. Failing that 9 mm Baltic ply would be an option. Give it a coat of sealer as it is prone to fungal attack - in my shed at least.

 

[amakah]

Glass for the back.

 

[thetyreman]

MDF is always dead flat, the downside being the weight but it'd be ideal for this you can get it in many different thicknesses,

hardboard or HDF is good but a bit thin, you can't get thicker than 3mm hardboard, I tried to find 6mm thick hardboard a while ago and nowhere had it in stock.

 

[MikeJhn]

The problem with any of the OSB type materials is the leaching of the glue over time staining the art work, special boards and even tape are used in most art work, but for this application I would try to source something like an off-cut of Bushboard from a bathroom fitter, does not have to be one piece.

 

[el_Pedr0]

Good info.

Thankfully, the osb leakage problem shouldn't affect my case because I've got the 9mm pinboard between the osb and the artwork.

 

[paulrbarnard]

Good info.

Thankfully, the osb leakage problem shouldn't affect my case because I've got the 9mm pinboard between the osb and the artwork.

The ‘off gas’ is acidic. Your pin board is probably porous so yellowing will happen over time. For my picture framing I buy acid free hardboard or MDF backing sheets. They are expensive but cheaper than trying to repair a yellowed art work. I also use an acid free foam core layer between the backing sheet and the art work.

It of course depends on how long you intend to hang it. Acid damage takes a few years to become noticeable.

 

[thetyreman]

The ‘off gas’ is acidic. Your pin board is probably porous so yellowing will happen over time. For my picture framing I buy acid free hardboard or MDF backing sheets. They are expensive but cheaper than trying to repair a yellowed art work. I also use an acid free foam core layer between the backing sheet and the art work.

It of course depends on how long you intend to hang it. Acid damage takes a few years to become noticeable.

one way around it would be to seal it with some kind of varnish or shellac.

 

[amakah]

What is wrong with glass at the back, you could also put something between the glass and the front to take the pins.