The sad realization that MDF is not flat :-(

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jerseyguy1996

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Joined 2013
#1
I've been working on my Tony Gee Proteus (aka Wilson Audio Cub clone) and Tony Gee Mezzo Proteus (aka I don't know) 5 speaker surround system and I am to the point of painting. I actually had no idea what a Wilson Audio Cub was but after seeing pictures of them recently, I am determined to do a similar paint scheme for my Proteuses (Proteui?) I am kinda just winging it in terms of painting these. I filled all of the seams and....ahem....dents created from me lugging these things around and knocking them into door jams......with elmers wood filler and sanded everything smooth. This is them all sanded and ready (so I thought) for paint.


IMAG0288 by jg1996business, on Flickr

Next I rollered on 3 coats of Kilz Original Oil Based Primer.


IMAG0297 by jg1996business, on Flickr

All of the speakers are primed like this.


IMAG0298 by jg1996business, on Flickr

Then I went to sand off the dimples in the primer and.......dang......to get down to smooth paint on the entire surface I end up sanding off most of the primer 😱


IMAG0295 by jg1996business, on Flickr

I guess, at least this gives me a chance to flatten everything out.
 
#6
whgeiger said:
For an automotive grade finish, check this out:
COUNTERTOP PAINT - GianiGranite.com - FAQ
The manufacturer claims it can be directly applied to a primed and sanded MDF surface to provide a finished surface as tough and water resistant as a melamine laminate.

Regards,

WHG
Click to expand...

Interesting stuff, but I wonder if it comes in solid colors. Speaking of automotive grade finishes, I had considered taking these down to the autobody shop at the end of my street to see if they could do them. I eventually decided not to because I want the finished product to be all me.
 
#8
I feel for you.

I'm building a pair of Wilmslow Audio Prestige Platinums.

After getting the MDF to an apparently perfect finish I applied primer - I might has well have flattened the MDF with a bulldozer.

In the end I've veneered the MDF but even that looks perfect until you start to apply any kind of finish.
 
#9
KatieandDad said:
I feel for you.

I'm building a pair of Wilmslow Audio Prestige Platinums.

After getting the MDF to an apparently perfect finish I applied primer - I might has well have flattened the MDF with a bulldozer.

In the end I've veneered the MDF but even that looks perfect until you start to apply any kind of finish.
Click to expand...

I'm trying to avoid rushing the painting process even though I really really want to start enjoying these speakers. I'm just going to keep priming and sanding until I have a perfect surface for the top coat.
 
#12
evanc said:
How are you going to apply your top coat?
Click to expand...

And therein lies the problem. Primer is one thing, it can be rolled on and sanded, but top coat is another. Sure it can be rolled on and sanded, then polished, but that is extremely difficult even for an expert. Sand a little too much in any one spot and you are through to the primer and it's time to start all over again. Basically the only way to get a very good final finish, like Wilson, is to spray it with a two part heated paint (just like automotive) that cures very fast. This still has to be done in a paint both or the dust (there is always dust) will kill you.

And then there is the fact that the MDF will warp with humidity unless completely sealed inside and out. This means that sanding it flat today does not mean that it will still be flat tomorrow or the next day when the humidity changes. I gave up on MDF. I just could not get a decent finish no matter what I tried to do. To me, that's why Wilson uses Corian (or similar acrylic sheet) because it does finish well.

And consider that some quality paints cannot go right on top of a lacquer based paint like your primer. Better would be (would have been) a good epoxy primer - which I believe you can still do over the lacquer.
 
#13
sangram said:
I always thought I was doing something wrong, needed about six coats of primer before I was able to start sanding.
Click to expand...

I tried using the old car sprays, before health n safety nannies banned it. 3 cans on one 15 litre box....

Sanded and ended up like the OP. after another few cans, it was ok. Just one helluva lot of paint and sanding. But then lacquering was the worst, maybe 7 or 8 coats...with 2 weeks hardening time between each. Painful.
 
#14
mondogenerator said:
I tried using the old car sprays, before health n safety nannies banned it. 3 cans on one 15 litre box....

Sanded and ended up like the OP. after another few cans, it was ok. Just one helluva lot of paint and sanding. But then lacquering was the worst, maybe 7 or 8 coats...with 2 weeks hardening time between each. Painful.
Click to expand...

I used 6 cans on this build (this stuff is not yet banned in India but after using it I can confidently say it should be)...

DIY Active Monitors | TechEnclave - Indian Technology Forum
 
#15
In finishing MDF the trick is to NOT break the surface.

How would you like to do this in one coat?

UVMaxGloss.jpg
 
#17
Better would be (would have been) a good epoxy primer - which I believe you can still do over the lacquer.

In this case I might go for the bin alcohol/shellac based primer. It dries fast sands well and is OK over under any paint.
 
#19
the big harware stores here and in the USA are selling an all in one paint that is primer and finishing coat all in one. I haven't worked with mdf a lot, when I work with wood its sand, sand, sealer, sand, varnish , sand .....varnish, 6 coats at least, and polish.
 
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