What is the best way to paint mdf?

[jeff_free69]

Re: What is the best way to paint mdf?

From my newbie-hacker handbook:

- Once you follow all the good advice about prepwork above - Stay away from GLOSS spray cans; choose SATIN instead.

- Heat the the cans in the sun or a bucket of hot water immediatlely before to use.

Gloss will drive you down a path towards perfection, or insanity trying to get there. With good prepwork, Satin can get good results with 2 -3 coats ( i do double coats - 15-20 minutes in between ; then let dry overnight, sand & repeat)

BTW Satin is close to "semi-gloss" & I don't think you can get semi-gloss (or flat) anymore, except maybe in black. At least that what I recently discovered after visits to 5 Lowes-Depots. I guess with only 2 choices they can sell more shades of lavender etc.

[weezbunbun]

Re: What is the best way to paint mdf?

Before I went into IT I was a painting contractor for 20 years. In my opinion the ONLY thing to use on raw wood, MDF or particle board is white laquer undercoat sprayed with an HVLP or airless. Builds heavy and dries quick. Sand with 220 grit and your ready for finish coat. Hopefully I'll have some pics of my tritrix and "The Drake" builds in the next few weeks.

[r-carpenter]

Re: What is the best way to paint mdf?

From my newbie-hacker handbook:

- Once you follow all the good advice about prepwork above - Stay away from GLOSS spray cans; choose SATIN instead.

- Heat the the cans in the sun or a bucket of hot water immediatlely before to use.

Gloss will drive you down a path towards perfection, or insanity trying to get there. With good prepwork Satin you can get good results with 2 -3 coats ( i do double coats - 15-20 minutes in between ; then let dry overnight & repeat)

BTW Satin is close to "semi-gloss" & I don't think you can get semi-gloss (or flat) anymore, except maybe in black. At least that what I recently discovered after visits to 5 Lowes-Depots. I guess with only 2 choices they can sell more shades of lavender etc.

You can get anything and everything in spray cans.

http://www.mohawk-finishing.com/

http://www.abbotpaint.com/

Abbot also has blank spray cans that they can fill and pressurize with custom color lacquer or whatever one desires.

[lunchmoney]

Re: What is the best way to paint mdf?

Here's a couple of pictures of my Tritrix's... sealed with a few coats of 50/50 wood glue/water, then primer and paint.

It's been almost 2 years, and they still look great... yes, the seams have emerged slightly, but no more so than when I used shellac on my center channel.

I used a similar approach on my SR71's with similar good results.

In conclusion, I don't believe that using a wood glue/water mixture is the big expansion disaster that many claim it to be... and getting seams to remain perfectly hidden forever is a much bigger issue than whether you use this approach vs shellac, etc.

[lunchmoney]

Re: What is the best way to paint mdf?

And by the way, the wood glue/water sanded much better than the shellac.

[mzisserson]

Re: What is the best way to paint mdf?

And by the way, the wood glue/water sanded much better than the shellac.

Hey! You coming to DIYNE this year?

[lunchmoney]

Re: What is the best way to paint mdf?

Hey! You coming to DIYNE this year?

I'd like to, although I got nothing new to bring.

When is it, Mr Threadjacker?

Email me.

[mzisserson]

Re: What is the best way to paint mdf?

I'd like to, although I got nothing new to bring.

When is it, Mr Threadjacker?

Email me.

Sorry, moment of gross spontaneity... Resume painting discussion :o

[davepellegrene]

Re: What is the best way to paint mdf?

dave, I hate to be a party popper here and believe me then I am critiquing you, it's only out of good intentions.
MDF expends and contracts differently thickness wise and lengthwise. This is why, then **** joints are used, ghosting takes place after a while. Instead of **** joint, use 45 miter or lock miter. Problem gone. Glued up edges of mdf now expend and contract at the same rate. Now, you can round over and glue size or veneer without much consequences.
Bondo and MDF do not have same expansion and contraction properties and while you have seal your channels in with the finish, it's a potential problem (and I hope I am wrong). Besides it's very time consuming.

I was really trying to stay out of this conversation. Been down this road a few times,
I agree with using a 45 degree angle when possible although on a good finish you can still spot the seam. I will say if you are looking that close it gives you something to see. Some are not able to build a six sided 45 degree angled box either do to skills are tools so the trench method gives them another choice. A lot of work, I don't know, depends on your skill level with body putty. I guess you also have to look at the time you spend on building a quality speaker it's really not that much more work.
I have also found its best to coat the whole piece and not just the trench so you don't have the transition point from body putty to wood. Putting any finish on top of the body putty to "seal" it isn't necessary to stop the seam from showing through. The body putty is just a buffer when the expansion/ contraction happens.
I still find MDF better to work with when painting than plywood. Being MDF is a compressed product I have found the more moisture you introduce to it the more it breaks down the glue causing expansion. With an excess of moisture added I believe it destabilizes it also magnifying the expansion/ contraction uncontrollably. Cutting a product like wood glue by half doesn't seem to be enough moisture to do this. I'm talking the moisture you get from products like Min Wax wood hardener, that just keep soaking in as long as you apply it, or anything thinned that much like overly thinned fiberglass resin. I also think it helps a lot to go slow with the finishing process allowing the moisture to dissipate before adding more.

Anyway wasn't this thread about painting MDF not hiding the seams in it?
Dave

[davepellegrene]

Re: What is the best way to paint mdf?

has anyone tried just laminating the whole box with something like masonite?

Dave that bronze satin looks great, ive been wanting to move away from black gloss..ugh.. what brand is that?

It was Krylon. I also used satin black first and liked that as well.

I think masonite will still have the same issues as MDF. Jim Holtz uses a method were he dado's the end like a ship lap joint so there is only about a 1/16" left to cover the end of the MDF. That seam can be hidden then in a round over to make it harder to see. Down side you have to be careful not to break of the thin edge.

Dave

[Sibelius40]

Re: What is the best way to paint mdf?

Kilz, Kilz, and more Kilz. I don't use the premium stuff, just the oil-base, regular white Kilz. I used about 4 coats on the Palladians, hitting the seams especially heavy, and followed that up with 2 coats of Hammered Copper Universal from Rust-Oleum. No signs of seams yet. It's been about 6 months. It does tax your patience to do it this way, because you're so close to being done and you want to see your creations in action; it's very tempting to skip a coat or two. But persevering and getting 4 good primer coats on will give you as good a base seal as you can get. It should feel like butter after you hit it with 400 sandpaper following that last coat. Hope this helps.

[lunchmoney]

Re: What is the best way to paint mdf?

Anyway wasn't this thread about painting MDF not hiding the seams in it

The two issues seem to be inextricably linked, which I question.

Perhaps the lady doth protest too much?

Yes, seams do tend to emerge. But it's very slight, and not really noticeable unless you're up close.

I question spending crazy amounts of time to achieve what's only a very slight visual difference, but that's just me.

[lunchmoney]

Re: What is the best way to paint mdf?

Kilz, Kilz, and more Kilz. I don't use the premium stuff, just the oil-base, regular white Kilz. I used about 4 coats on the Palladians, hitting the seams especially heavy, and followed that up with 2 coats of Hammered Copper Universal from Rust-Oleum. No signs of seams yet. It's been about 6 months.

Report back again in another 6 months ;)... you'd be amazed how seams will eventually emerge.

[Sibelius40]

Re: What is the best way to paint mdf?

The two issues seem to be inextricably linked, which I question.

Perhaps the lady doth protest too much?

Yes, seams do tend to emerge. But it's very slight, and not really noticeable unless you're up close.

I question spending crazy amounts of time to achieve what's only a very slight visual difference, but that's just me.

Yes, and the OP did ask about painting the end grain. I also think this can go to unnecessary extremes. Painting requires patience for good results, however, there are limits to everything.

In reply to your previous post, I am not worried aboput seams, because they are so slight in any event. No one besides me will ever likely notice or care enough to comment.

[lunchmoney]

Re: What is the best way to paint mdf?

has anyone tried just laminating the whole box with something like masonite?

Tricky if you want to radius the edges. There are audible reasons why it's important to radius the edges of the baffle.