MDF porosity

[Pete Marsden]

I'm sure everyone will say ''I knew that!'', but having used MDF to make vacuum boxes for years (canopy moulding), I've just found out it's porous.
I wanted to lay up a large sheet of glass and my ex double-glazing panel wasn't quite big enough so I tried 9mm MDF. Could I pull a decent vacuum? could I 'ell. Turns out the air was being drawn right through the panel.
Two coats of polyurethane varnish has cured this although lots was required around the edges.
You live and (sometimes) learn!

[VinceC]

Almost as porous as my wallet. Thanks for the heads up

[Simon WS]

It'll swell and soak up a lot of moisture too if you don't keep it dry.

[Jolly Roger]

..and whilst we're kicking MDF, the dust from it is lethal. Think asbestos. So please wear a dust mask if you value your health.

[Paul W]

..and whilst we're kicking MDF, the dust from it is lethal. Think asbestos. So please wear a dust mask if you value your health.

Could you point me in the direction of some literature on this please Roger.

I've heard this said about MDF many times and yet never found any evidence to back it up. Nowadays it is acknowledged that breathing any wood dust carries an element of risk to health, but as MDF is widely available and used in school tech/design/resistant materials (woodworking) classes, it seems odd to me that it carries the same health risk as those associated with asbestos.

[Barry_Cole]

The stuff is banned in many countries, but it seems that we are expendable....



BC

[Jolly Roger]

Thanks to Paul for his query and Cliff for his link.
I agree MDF is less hazardous than asbestos, but I think it's wise always to be aware that it can cause cancer.
A cabinetmaker friend told me that if you work with any material long enough, it will end up inside you. I think he's probably right.
In the case of MDF it's the formaldehyde resin-coated particles generated by cutting or sanding with high rpm power tools that worry me. It's not so much the dust that covers everything in your workshop, but the tiny (sub 0.5 micron) particles that pass through cheap masks and penetrate deepest into our lungs.
Like all things though we balance the risk of any activity with the benefits of doing it. My compromise is to use a decent HEPA mask and work outside if possible when using MDF and power tools. Inside my workshop I have various dust extraction equipment.
Take care.
Rog
P.s. When I was young and invincible I took no precautions!

[Chris Hurst]

I agree MDF is less hazardous than asbestos, but I think it's wise always to be aware that it can cause cancer.

But of course at one point asbestos was the wonder building material that everybody had been waiting for. During the war troops were issued with cigarettes! Only later were the dangers understood.

My local building merchants won't bulk cut tanalised timber even with proper industrial dust extraction. But, strangely they will cut sheets of MDF to size!

I wonder for how much longer?

[Jolly Roger]

I know what you mean Chris. History makes fools of us all!

Remember the snow scene in Wizard of Oz? Yep - they're wading around in clouds of asbestos.

Contrast this with today. There's a small panel of asbestos above a window in my classroom. It's been sealed with special paint, labelled as hazardous, and if it gets as much as a drawing pin in it, it's a notifiable incident. We seem to go from one extreme to another.