How smooth can it possibly be made?

[Akuma]

Hello everyone.

I reached the state of painting my scratchbuild cab and at the moment I don't know what to think. In detail I don't know if I should be pleased with the current results or if I can do better.

When painting a cab made out of MDF, I wonder how smooth it can possibly be made. As smooth as plastic - so shiny that it can be mistaken with the plexi covering the CPO? Or will a little structure remain? I decided to paint the cab white and (besides using the obligatory foam roller) am using an acrylic based paint that is paint and primer in one. So far (5 coats total)  I am satisfied with the outcome, even though I think it will need 3 or more additional coats. It's just that there is a slight structure which even remains after sanding in between. You can actually only tell when you got your face about 5 cm (2 inch) away from it and it feels rather smooth but ,sigh, not totally smooth.

Another additional question: When painting the sides - should I put an amount of paint, big enough to cover the whole side, on it or should I apply it in patches using only as much paint as the foam roller can contain? I used the second technique so far but when viewing from afar, you see that the colour is not really even. Or is this because of the white colour - will it only take some more coats to look even?

[TOK]

If you're looking to get the level of finish you'd see on something like a piano, I don't think you're going to get there with a foam roller. You'd need to spray, wetsand, polish and clearcoat. You could probably sand and wetsand your roller job and get it very nice, but not perfect.

I always kind of felt these things were mass produced and quickly stenciled & sprayed. Perfection isn't actually very authentic. Definitely understand if you're looking for something better in your home though!

[Akuma]

Actually this answer is okay for me - I mean what you are saying is that I did the best I could using the stuff I got, so everything is cool as I can say - I did the best I could do : )

[javeryh]

You can get it really really really really really smooth.  Take a look at my project thread for Bella's Arcade or The Coder's Xbox Driving Cabinet.  We both used MDF and put an automotive finish on.  The first thing people say when they see my cab is "where did you get the thick pink plastic to make the sides out of?"  It didn't come out 100% perfect like a piano (although that was the goal) but I came really close. 

After several coats of primer and paint (with a high quality foam roller) I applied 25 coats of clear lacquer and sanded it down to 1500 grit.  Then I applied an automotive rubbing compound and wax for the top coat.  It really shines, there are no visible brush or roller marks and it is super smooth to the touch - like plastic.

[Akuma]

Do you exactly remember how many coats of primer and paint? Did you sand between primer / paint coats? How did you apply the clear lacquer? I have no possibility to spraypaint btw

[javeryh]

This is basically what  I did:

1.  Sanded MDF with 600 grit to get it as smooth as possible
2.  Applied OIL-based primer - rolled on with a 4" foam roller (2 coats).  Sanding after the 2nd coat with 220 grit.
3.  Applied water-based pink paint - rolled on with a 4" foam roller (6 coats).  Sanding after the 2nd, 4th and 5th coats with 220 grit.
4.  Sprayed on 25 coats of lacquer straight from the can - no sanding.
5.  Wetsanded like crazy with 1500 grit - I spent 8 hours just on this step
6.  Applied rubbing compound with soft cotton rag (2 coats)
7.  Applied polish with soft cotton rag and buffer (2 coats)

HERE are a few good shots of the difference the rubbing compound/polish makes.

I did not have access to any spraying tools/materials, unfortunately.  The lacquer was easy to apply though - I did it all in one weekend since each coat dried in 20 minutes.  I couldn't get it perfect but the finish still looks 1,000,000 times better than leaving brushstrokes on there with ordinary paint, IMO.  It almost looks like it came from the factory or something.

Good luck with whatever you decide to do - I'd be happy to answer any questions if I can...   

[scotthh]

Insanely smooth, see HoopstarsGarage's Centicade, especially the parts about how he finished the CP.

[sstorkel]

Rather than spraying on 25 coats of lacquer, I'd recommend brushing on 4-6. You can get a much thicker finish in much less time. Lacquer dissolves and bonds with previous coats and it sands well so you don't have to worry too much about brush marks. The incredibly toxic solvents flash off very quickly, so you can easily brush on multiple coats in a single day. Let the whole thing cure and then start sanding!

FYI, my experience with Deft brushing lacquer is that it takes 2-4 weeks to cure completely and reach full hardness. It's dry within an hour or two, but still scratches easily for the first couple of weeks.

javeryh doesn't make it clear, but you probably don't want to start sanding with 1500 grit paper. Start at 600 grit, or maybe even 320 or 400 if you've got a lot of brush marks, and sand lightly for a short amount of time. You just want to see uniform scratch marks over the entire surface. Then you move the the next higher grit of sandpaper and repeat the process. By working up through the grits, you'll spend less total time sanding. By the time you reach 2000 grit, you should have a smooth, glass-like finish!

You definitely want to practice on a piece of scrap wood before you attack your project, though. This is especially true if you're going to try 320- or 400-grit paper; if you get too aggressive with them, you can ruin the finish pretty quickly.

[releasedtruth]

You really want it smooth? Laminate 

You guys that paint get some great results and I applaud the efforts. I whipped out the router and trimmed all the laminate (lot of it to trim too. Great hard surface finish that looks smooth and silky.