Sanding Masonite

[boneaus]

I have some unpainted masonite panels that has some dings and scrapes that I want to prepare for painting. Can raw masonite be prepared for painting like timber i.e. filled with wood filler and sanded smooth? Or will sanding rough up the smooth finish?

[Kev Y.]

boneaus, I think you will fond that any sanding on Masonite will leave visible scratches. Not too sure if there is any way around that. HOWEVER you may be able to undercoat the surface first, then apply the filler and lightly sand then apply a second light coat of undercoat.

[rogerjenkins]

Been there,- done that !! YEP,- Idea does work !! Dings & dents,- fill as you would with real timber, - BUT don't use real coarse grade sandpaper,- Use 120 - 150 grit, or even 180 grit, then you shouldn't have any scratching problems. Also don't use too much sanding pressure either, otherwise you will end up with a bigger mess, and, ( worse ), heaps of very noticeable scratches. To seal afterwards recommend two coats of Undercoat, or Primer-surfacer, lightly sanded between coats. You will have to fine sand the entire Masonite surface to, " key," the surface for the Undercoat / Primer-surfacer to adhere to the Masonite.
** This also works with dings & dents in MDF / Chipboard / Plywood panels too.
'ave a good day, & happy woodworking,
Roger

[boneaus]

Thanks for the info guys. I will practice on some scrap pieces. I want want to prepare the surface for a nice black satin finish. Unfortunately black is not the best colour to hide blemishes but at least I am not after a piano black finish.

[soundman]

exactly what are you making and trying to achieve.

there are a couple of tricks that can be done with masonite.

If you treat it right it finishes very well.

cheers

[boneaus]

exactly what are you making and trying to achieve.

With a username of Soundman I assume you are into audio, right? So am I. I am building my next set of "last ever" loudspeakers. I have used 4.8 mm masonite to face the baffles as an easy way to rebate the drivers.. So instead of the usual mdf I have masonite facing on the baffle. I expected the masonite to give a better finish to mdf which is very porous and needs a couple of sealing coats. As it turned out, masonite has a harder surface but is not that smooth. It turned out ok with the tips I was given.

[soundman]

Always glad to hear that I have helped.

Unfortunately masonite is a product that is falling from favor, but if you play to its strengths, it can be a fabulous material

I have a pair of speakers in fron of me that are from memory 6 litre ported boxes in a tower format with single 4 inch wide range drivers.

because these soeakers require a thin baffle becuse of some of the clerance issues I used 10mm sign board (which is a masonite variant)

they sound great and they finished up in black nitro realy well.

Masonite is pretty dense, good and hard and has pretty good strength and rigidity for its thickness.

for future reference masonite clear finishes very well.....go at it with a clear sanding sealer and a good clear top coat and it comes up realy deep and dark, almost ebony

used in combination with other board products, it can meke beautifull contrasts.

imagine the boxes you picture done in ply with the masonite faces as shown......all concieled fastenings and sanded flush on the edges.

gorgeous.

good work.

I hope they make you happy.

Damn I got build some speakers soon.
I used to build quite a few speakers.

cheers

[soundman]

If ya want a realy good material lay ya hands on some "tempered masonite"

That stuff is hard.

A bit hard on tools though.

cheers

[boneaus]

I used 9 mm marine ply over a 25 mm mdf layers plus a damping layer. I will track down some tempered masonite as a potential outer layer instead of marine ply for a future project. It should be cheaper and allow me to use a spray paint finish instead of stain and clear coat.

[soundman]

it can look realy good as a contrast to ply under a clear.

MDF its self laquers up pretty well if you choke it up properly with undercoats or sealers first..

cheers