Advise on re-finishing MDF

rbrb · « **on:** 31 Oct 2005, 06:36 pm »

I stipped off the vinyl covering on my speakers and am now left with the raw MDF. The surface seems quite porous.

Does anyone have any hints on what to use and how to seal the MDF and prepare it for painting? What grit of sand paper, type of sealer/primer etc. Any help would be appreciated.

bubba966 · « **Reply #1 on:** 31 Oct 2005, 06:51 pm »

Quote from: rbrb

I stipped off the vinyl covering on my speakers and am now left with the raw MDF. The surface seems quite porous.

Hmmm. That doesn't sound like MDF. That sounds more like particle board. Doesn't sound like it's even industrial grade particle board.

Quote from: rbrb

Does anyone have any hints on what to use and how to seal the MDF and prepare it for painting? What grit of sand paper, type of sealer/primer etc. Any help would be appreciated.

Well, if it's regular old particle board like I'm guessing it is using a proper filler would be the way to start. A finer automotive body filler (something a lot finer/smoother than Bondo) should be used to smooth it out. 3M makes a good one though I've not used it in a while so I don't recall the name of it. But any autobody shop should be able to help you out with that.

Then you could probably start with 80 grit after you've used the auto body filler to smooth it out. Depending on how far you want to take it you might want to go to 120 after that. Then 220, 320, 400.

Or if you have to start with a coarser grit to smooth the filler out you might go 60, 80, 120, 180, 220, 320, 400.

What type of finish are you putting on it? That in itself will determine how the filling/smoothing should be done & what type of sealer or primer needs to be used.

rbrb · « **Reply #2 on:** 31 Oct 2005, 07:08 pm »

I may be wrong but it does not appear to be particle board. Somes areas have reamained smooth but other parts are now rough where a small amount of material lifted off with the glue from the vinyl. I will verify whether it is in fact MDF.

I think I should have said fibreous ( if that's a word)rather than porous in my original post.

I want to finish them in a silver color similar to a car's finish. Wilson or Meridian speakers come to mind for the look I'm trying to achieve. I really have no idea as to what kind of paint I should be using.

Thanks

ooheadsoo · « **Reply #3 on:** 31 Oct 2005, 07:22 pm »

Car finish? How about automotive paint?

Also, Bondo+primer should be ok, IMO, but if you have money to spare, I guess you could consider some industrial 3M filler.

What you are describing does potentially sound like roughed up mdf.

skrivis · « **Reply #4 on:** 31 Oct 2005, 09:22 pm »

Quote from: ooheadsoo

Car finish? How about automotive paint?

Also, Bondo+primer should be ok, IMO, but if you have money to spare, I guess you could consider some industrial 3M filler.

What you are describing does potentially sound like roughed up mdf.

It might even be a combo of rough MDF where the surface was removed, and some leftover adhesive from the vinyl.

Something like spackling compound or finish plaster might work too. It can be thinner in consistency than bondo, so it might be easier to work with.

thayerg · « **Reply #5 on:** 31 Oct 2005, 09:57 pm »

Or use aluminum look laminate and spare yourself the tedium of bondo, sanding, bondo, sanding, sanding, sanding, sanding.

skrivis · « **Reply #6 on:** 31 Oct 2005, 09:59 pm »

Quote from: thayerg

Or use aluminum look laminate and spare yourself the tedium of bondo, sanding, bondo, sanding, sanding, sanding, sanding.

Sounds like a good idea to me.

fajimr · « **Reply #7 on:** 31 Oct 2005, 11:19 pm »

I was just reading a thread on racks and there was a link to a DIY rack with MDF shelves: http://www.tnt-audio.com/clinica/flexye.html

the author suggested painting with damping paint.... it would probably cover up any rough finish and might be interesting depending on the look you were after

rbrb · « **Reply #8 on:** 31 Oct 2005, 11:43 pm »

Quote from: thayerg

Or use aluminum look laminate and spare yourself the tedium of bondo, sanding, bondo, sanding, sanding, sanding, sanding.

I have thought about that but I don't have any right angle corners. All 4 corners are rounded off. How bendable is laminate?

thayerg · « **Reply #9 on:** 31 Oct 2005, 11:55 pm »

Depends on the product. Some laminate is very formable, although the radiuses on a speaker might not work. You can cut narrow strips of laminate and lay them lengthwise along the curve but it's probably not worth the effort.

Another option might be to cover the cabinet with some kind of mesh or metal textile. You could even have fun with screen door material.