"Sealing MDF terrain boards" Topic

Hi folks,

I am planning a series of 1' by 1' MDF terrain boards (1/8" thick) and wondered how others have sealed or otherwise protected MDF terrain bases against warping. I'd rather not cut battens or braces to affix underneath them, if possible (too much cutting, too much thickness to store easily). I have tested several pieces by applying paint and then ground work already; unprimed or unsealed MDF warped slightly, but noticeably, in half the cases after only a few days. Those with ground work applied direct to the MDF (artist's paste and resin) have not yet warped. I just sprayed a couple of others with grey primer and will then try ground work over that.

Any suggestions on a process to prevent warping would be appreciated.
Thank you in advance.

I have had luck sealing both sides with brushed on polyurethane. I usually don't have to much trouble with MDF warping, but painting only one side is usually not a good idea.

Sealing both sides with a polyurethane is your best bet as AoW said above. Difficult stuff to prevent warping. When you apply anything to it, it tends to warp to some degree.

Use an 'oil' based paint, either sprayed or brushed onto all surfaces – MDF does not react kindly to water based paints or sealers, and even less so to spilt drinks.

With thin sheets you will have trouble regardless, try to have the back with as many layers of paint as the front to even out the rate of moisture exchange

At 300mm square I'd have gone for 9mm or 12mm MDF rather than 6mm, I doubt you'd have had as much warping with thicker stuff.

Another trick is to stick two 3.5mm MDF sheets together – that has worked for me in the past.

I agree with GildasFacit.
We have dozens of 8" x 8" mdf boards, 1/4" thick, and we haven't had any warping (four or five years old).

Plus, if you use 1/4" for your regular terrain squares, you can use two pieces of 1/8" to cut out rivers or roads and give them some depth. We did that too, and again, no warping so far.

No way to test it, but it might matter where you are, and where you store them as well. Humidity and all that.

I did a pair of 2x2' boards recently, and came up with a trick. Turns out if you paint one side, let it dry, and paint the other, you got your warping going on. So I painted one side, everywhere but the four corners – they each had a 3x3" unpainted spot. Then I used those spots to clamp the boards back to back while they dried. They couldn't curl as they dried because of the clamps. When the paint was dry, reverse and repeat. Paint the corners later. I was working with 1/2" stock, though. 1/8" is tough. Maybe put a heavy weight in the center and paint all around it? Flip, repeat, paint the centers last?

Good luck!

Andrew

Thank you all very much for the helpful comments. I think I will upgrade to 1/4" inch and seal both sides with polyurethane before trying again. The 1/8" x 2 for rivers or other sunken features is also interesting. Thanks again!

You can also try water-resistent MDF which is much less prone to warping. A bit more expensive and its a pale green colour to distinguish it.

MDF ?

John

medium density fibreboard

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A type of particle board.

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