Painting MDF, how?

[pochoboy]

My 1st subwoofer build and I've got my box all glued together and will use veneer on front,sides and top panels. I purchased a can of Rustoleum red primer(wet/dry sandable, now I'm not going to wet sand my mdf thats for sure) and rustoluem gloss back to paint my bottom and rear panels. Now, do I just spray the red primer on the bare mdf or could I brush on house primer by the name of "Gripper" from Home Depot? Then sand it and spray the Red Primer? The Gripper cleans up with water so I would assume its a latex primer.

I've also purchased sand paper and according to the label. 150 is used prior to priming and I got 220 for light sanding between stain, primer, sealers(my guess its used inbetween coats of primer paint) and finally I got the 320 for between coats of the finishing paint.

hope I got this all right.

[5m3g_head]

Re: Painting MDF, how?

When I painted some MDF I used a special primer/sealer. MDF soaks up paint unless its sealed.
I brushed it on and sanded it before painting colour.

[Zero the Hero]

Re: Painting MDF, how?

really should use an oil based primer on MDF since water and MDF don't mix well. It may be fine or it may start to raise a bit from expansion.

[lunchmoney]

Re: Painting MDF, how?

Do a search. There are many threads on this topic.

[gowa]

Re: Painting MDF, how?

Try this:

http://www.diyaudio.com/forums/showthread.php?threadid=83141&highlight=

[pochoboy]

Re: Painting MDF, how?

okay I screwed it up already but still can recover from my mistake. After using my router with a flush edge bit I sanded the edge and the panel taking off the outer sheen of the MDF.

Guess I'm gonna have to look for that primer sealer stuff

[lunchmoney]

Re: Painting MDF, how?

okay I screwed it up already but still can recover from my mistake. After using my router with a flush edge bit I sanded the edge and the panel taking off the outer sheen of the MDF.

Guess I'm gonna have to look for that primer sealer stuff

Even if you hadn't sanded off the sheen, you still need to seal the mdf prior to painting.

I use a 50/50 combination of wood glue and water, 4-5 coats. Works great...

[davepellegrene]

Re: Painting MDF, how?

The red primer you mention is not a water base and should be fine to use for building up. Like Lunchmoney said seal the mdf first. His method works good. I like to use Bin 123 alcohol base. Builds good dries fast. Either method will get it done. Seal the ends as you are coating over and over. Let dry! Sand. Now you are ready for the primer you bought. Spray as it says on the can. Now when you start sanding you will have a base of one color with the red on top. When you sand through the red you will be able to see your imperfections easier. Your primer should look just like the link gowa gave you when you are ready for paint. The part were he is ready for compound. I wouldn't sand with any finer then 220-320 on the primer. Main thing to remember let dry between coats. If you don't get powder when sanding its not dry enough. Now you are ready for paint and follow gowa's link. Very good. It also wouldnt hurt to let dry for several days. Your primer will shrink for up the 30 days and with a high gloss it will show.
Good luck Dave

[brianpowers27]

Re: Painting MDF, how?

I wouldn't recommend adding water to glue. The extra water could expand the MDF.

On all of the MDF projects where I have found success, I used exactly one coat of undilluted Elmer's wood glue accross the entire MDF surface. I only wait about 1.5 hours for it to dry before moving on (70f degrees)(I purchased the gallon jug). Fire up the random orbital sander with a 320 grit disc and go to town.

I give it a light sanding and then I move on to any standard primer. I have even primed using bin latex primer. The latex tends to contract and then crack, so >1 coat might be ncessary. Otherwise, finish as you normally do.

[johnnyrichards]

Re: Painting MDF, how?

I just primer the stuff to death. Like ten coats or better. The "ends" of the MDF I hit with some latex wood filler and then sand. Otherwise, just a ton of primer.

[gowa]

Re: Painting MDF, how?

I spoke to a local cabinet maker and it seems that for some reason, auto products work well for MDF. Filler, primer & paint.

[davepellegrene]

Re: Painting MDF, how?

I spoke to a local cabinet maker and it seems that for some reason, auto products work well for MDF. Filler, primer & paint.

I have only used auto paint on my speakers so far. First set a year ago. No problems so far and sprayed on the MDF I think easier then on an auto. I also think the link you gave would be munch easier to duplicate with auto gun and paint.

[pochoboy]

Re: Painting MDF, how?

I'm not looking for a piano black finish but just a smooth black finish for the bottom and rear panels. Don't know why I chose the glossy black spray but it was either that or flat black Rustoleum. Maybe I'll exchange the black glossy for the flat black instead as I've still got the reciept.

Thank you for all the info and it looks like there's alot of options on the method of going about this.

[johnnyrichards]

Re: Painting MDF, how?

Consider the "satin" or "semi-gloss" black. It gives a much better finish than the flat black, and is more forgiving than the glossy.

[Æ]

Re: Painting MDF, how?

really should use an oil based primer on MDF since water and MDF don't mix well. It may be fine or it may start to raise a bit from expansion.

Yes, anything water based is dangerous for MDF. I wouldn't even chance using something water based. Not even water based glue.