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What's the best way to sand and spray paint particle board?

Hi All,

Trying to make replacement bases for my floor-standing speakers.  The originals were made out of particle board and appear to have a black spray-paint finish.  They were destroyed in the post when the person sending me the speakers failed to package them properly.  I now have the particle board cut to the right shape and I have begun the process of sanding.  It is my intention to spray a primer on, sand, spray a top coat, and then spray some sort of finish.  so here are my questions:

(1) I have sanded the board down with successively finer sandpaper and finished with 1500 grit wet and dry.  This is a very smooth finish until you wipe away the dust at which point it becomes rough-ish again.  Having done a bit of research I am now concerned that I have sanded the board down a bit to much, some forums suggest taking the board down only as far as 250 grit before spraying on the primer.  What should be my finishing grit before spraying on the primer?  My assumption was the finer the better but I'm not too sure now.  If the finish should be fine then how do I remove those stubborn fibers?

(2) what type of spray primer works best with particle board?  There seems to be a multitude but most of the information related to car/auto body work.  

(3) what grit of paper should I use on the primer?

(4) what should I use as a top coat?

Much thanks in advance
Ross

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instead of particle board can you use MDF? its a little smoother

rcgraham (author)  thematthatter3 years ago

Hi thematthatter,

I always get confused between particle board and MDF - this is what I have used (see picture) - it may well be MDF!

P1070906.JPG

that looks like mdf to me but im no expert on woods.

rcgraham (author) 3 years ago

As you may all have guessed from my replies I know very little about painting. Thank for taking the time to reply. I probably should have just posted a picture of the original in the first place!

rcgraham (author)  rcgraham3 years ago

with pictures - origional and replacement

P1070904.JPGP1070906.JPG
Vyger rcgraham3 years ago

That is covered with paper not paint. It is the same as for many panelings. That is why its white around the torn egdes. It is a thin paper that is glued to the wood and then covered with a finish. You can't really duplicate it as far as I know.

Instead, use a flat latex paint and brush it on. Then after it is dry sand it very lightly and coat it with a low luster water base clear finish. I think that will give you something close.

Typically particle board isn't painted. What you think is black paint is probably a black laminate.

rcgraham (author)  mpilchfamily3 years ago

Hi mpilchfamily,

I'm pretty sure the origional is painted - see attached. Particle board/MDF I'm never too sure what the difference is

P1070904.JPG

Interesting.

Kiteman3 years ago

The stuff you put on first isn't "primer", it's "sealer", often called "sanding sealer".

Unfortunately, you are never going to get a smooth finish on actual particle board, because the board is full of cavities between the glued fragments of wood - no matter how deep you go, or how fine your paper, you will always reveal more cavities.

As mpilchfamily said, the black layer was probably a black plastic laminate. You could either try replicating it by gluing on a layer of thick paper, or just accept the finish the way it is.

rcgraham (author)  Kiteman3 years ago

Hi Kiteman,

If I apply sanding sealer and then sand down smooth will the primer have enough of a surface to stick to?

You're missing my point - sanding sealer is used to make the wood sandable, and then you varnish or paint it. You don't need a primer, unless colour show-through is an issue.

Burf3 years ago

You should have applied a filler/sealer to the wood before painting. I would resand it thoroughly, apply the filler/sealer and then repaint using the primer and then the top coats.

As for the type of primer to use, once you have filled and sealed the wood, most any primer and paint compatible with the filler/sealer will work fine.

rcgraham (author)  Burf3 years ago

Hi Burf,

Thanks for your reply. I had thought about applying a filler/sealer and then sanding. my concern was that the surface would be too smooth for the primer to stick properly. I have read some posts, including the one above from Vyger, which suggests that the surface should be a little rough so that the paint/primer can adhere properly. If I apply filler/sealer and then sand down will I not face this problem, if not then why apply the sealer/filler in the first place as I can get the particle board relatively smooth - does the filler/sealer provide a smooth layer the primer can stick to?

cheers

Burf rcgraham3 years ago

When you sand the filler/sealer finish it off with 220 grit sandpaper, then apply your primer. A 220 finish has more than enough bite to hold any primer you wish to use.

Burf Burf3 years ago

Oh and yes, filler/sealer is specifically designed to fill the small pores and voids in the wood surface and then be painted over. It may require two or more applications to to get completely sealed but that is precisely what it is supposed to do, isolate the wood from the primer and paint applied over it.

Vyger3 years ago

Another thing that they often do with particle board is glue a type of wall paper to it. That is how cheap furniture is often made. Its a paper that simulates the wood grain. Then it is coated with finish.

If you want a real wood finish you can get a veneer wood and glue it to the particle board. Its very thin shaved wood. A lot of cheaper shelves are made this way. Like an oak veneer glued to particle board.

Another option is to use a paint roller with a thick nap. And use a latex semi gloss paint. This will give you a texture effect that will hide the particle board look. You don't sand this at all, just add a few coats and work it until it looks like what you want.

By the way, 1500 grit is for polishing, way finer than what you want for a wood finish unless you want it to look like a mirror.

And one more comment: applying a finish to bare wood causes the grain to rise. This makes the wood very rough again after you have sanded it down. This is why it needs to be sanded in between coats. It takes progressive coats to build up a good finish with sanding with fine grit in between each coat. Part of the purpose of sanding progressive coats is to roughen the last coat so the next coat has something to grip to. It is only the last coat that you would use the 1500 grit on.

rcgraham (author)  Vyger3 years ago

Hi Vyger,

Thanks for your response. I am trying to replicate the look of original base so that if I ever choose to sell the speakers on the bases wont look too out of place. I take your point about 1500 grit - the surface is now very smooth! the reason why I sanded down so much is because I suspect the original was done this way. The original seems to have a wafer thin layer of paint - the only way I can think that they achieved the finish was by sanding down to a very smooth level and then spraying over. see the picture attached to my reply to mpilchfamily.

Cheers