Hello all;
I made a nice base for a dio with MDF. I had it done ,sealed ,celuclay, and painted the trim . All looked great ,then a week or so later it was totaly warped. How do seal MDF well so this does not happen ? The base is about 20' x 30' and has curves cut in it. Should I use Plywood ? I was going to put long supports under it , would that help ?

SG61 ...............

MDF is nothing more than Compressed paper...... it's gonna suck up any moisture it can.... What did you seal it with?

Mitch,
Having had this very problem what I do now is to cover the MDF base with Cling Film, the kitchen food wrap is it called Saran in the States, add the Spackle or Celluclay, press in any detail like tracks, then once it is fully dry, remove the groundwork from the base, pait it the basic ground etc, then after staining/varnishing the MDF, glue the groundwork to the base with what we call no more nails, a strong white glue. Then add the vehicle and other bits etc.
This stops the warping and painting the groundwork as a seperate item is easier too.

Hope this helps.

John

Wow - 20x30 is pretty big.
I would do a couple of things. I would make strips of hardwood about half inch square and as wide as the base. Then screw them into the bottom to 'pull' the base flat. Then add a bit more decorative trim to cover the stiffening strips.
You should also use laquer or varnish and totally seal the entire base top and bottom. Let it dry between layers and plan on a few layers.

Make sure to hit the edges of the MDF with alot of sealer as they're like a Sponge.......... the surface of MDF is "tempered" so it's a bit harder. and less pourous

Hi Mitch,
I work as an interior decorator so i can really sympathise with what you have gone through,i've had my fair share of cupboard doors gone botched..Anyways,the best way to treat the mdf is just as Scott mentioned;paint the WHOLE sheet in a oil based ground coat.Usually the first coat will tend to dry out quite quickly,if you wait a short while you can eventually add a second coat to be sure.
Good luck with dio mate,
Cheers Shay

Hi Mitch

There are various ways to stop this, the one I use is PVA glue mixed with water, paint it all over the board, top bottom and sides and make sure you put more on the edges/sides than on the faces as Matt said they are like a sponge.

Not trying to get too technical MDF when it's produced has all the moisture removed,so adding anything to it without sealing it will cause the bowing you have found. I had the same thing happen to me, until I joined the timber trade.

Happy modelling Ross