Help with MDF finish/protection

[tuen]

Hi everyone,

I'm a long time lurker. I recently built myself a simple router table out of mainly MDF and I need some advice on finishing and protecting the MDF surface. I know that if the surface starts absorbing water, especially through the cut edges, the board will start bloating and warping (like what's happening in my bathroom). I did a search, but couldn't even find the word MDF in this section. So any advice on what sort of finish to use on my mdf board (obtained from Bunnings) would be very much appreciated. Can I just rub in Tung oil or something similar? Will this be enough protection from water, considering that I don't really care about the aesthetics of my router table. Thanks!

Justin

[RedShirtGuy]

This might not be of much use, but I'll tell you what I did with one of my router tables, and most recently, a new top for my scroll saw...

The Laminex factory/assembly places are close to me (in Ballarat/Wendouree) so I nipped down there and was able to get a honking great big sheet (~1.8m x 4m) of water stained Laminex rather cheaply (I *think* it was between $20 and $50). They have ooooooooodles of "unusable" product that they sell off for, as I was told, "beer money for the boys", but they only sell whole sheets so you end up with a lot to spare.

Using contact adhesive I glued it down flat to the top and bottom of the table, edged it all round with more of the same and trimmed it up with a flush bearing bit. That seals it all up and gives you a really nice, smooth, waxable top to work on.

The edging that was available at Bunnings was comparitively expensive and wasn't wide enough anyway.

The problem with the big sheets though is if you get a crack or tear at an edge, it's a bugger to stop it going down the whole length (particularly when rolling it up again for storage - which can be a nightmare in itself if you're doing it on your own).

[Ekim]

Justin,


This is what I recently did with a MDF top on a workshop cabinet.
Sealed the edges with a wash of Titebond 3 PVA glue mixed with a little water (2 coats). The wash was painted on with a broad artist brush (Bunning). Once dry the edges were sanded with 400 grit sand paper. Titebond 3 is water proof when dry.
The top (and edges) was then vanished with Cabot's Stain & Varnish, a one step oil based product. The colours are pre-packaged - I used "Red Mahogany (2 coats) to get the depth of colour that I wanted.
The final step was one coat of Cabots' oil based satin polyurethane.
Titebond 3 is sold by Carbatec.

The process is tedious but well worth the effort.



HTH

Mike

[Master Splinter]

Three coats of marine epoxy and you should be able to throw it in a bucket of water with relative impunity.

http://www.westsystem.com/ss/moisture-exclusion-effectiveness/

[tuen]

Thanks for the quick responses. Really appreciate the advice.

Any other methods of finishing, anyone else?

[malb]

If you were willing to go to a paint finish, MDF surfaces will accept paint and finish well. The issue is the edges, which don't finish well if just primed and painted. One solution there is to coat the edges with Gyprock Topcoat (the surface finish compound for joints in Gyprock sheeting) theb sand back to a smooth surface. This will then prime and paint like the sheet surface and produce an even colour and cover.

May not be practical for the actual table surface unless you use a two pack type paint, but definitely worthwhile for the cabinet if it has one. Personally I would laminate both sides of the top and either edge with laminate or with solid timber. A few coats of varnish or shellac should seal the rebate for the router mounting plate if used.