MDF sealant for Black Lacquer Finish

[Solid-State]

I'm curious what lacquer based sanding sealer people are using these days to apply a black lacquer finish to MDF. I need to be able to source it in Canada as well. This info was taken from ShopBot forum from a very experienced MDF cabinet maker.

"To get the best results, I suggest this procedure and you will get good results and as you refine it you will get perfect results.

1. Sand all edges with 150-180g
2. sand all edges with 200-300g
3. primer using a lacquer based sanding sealer
4. sand whole thing with 300g
5. add another coat of sanding sealer and another if needed.
6. paint as usual...

By using that process you will get a bullet proof finish. Heres why...

first you are sanding to remove any machining marks, then you are "burnishing" with 200-300g.

What this means is you are using the micro dust to seal the edges as you are sanding.

Then by adding the sanding sealer you are in effect making a surfboard type of finish, the sanding sealer soaks into the pores making it one solid surface."

From reading other posts on this forum others seem to have the best success using either shalak or a lacquer sanding sealer.

I'm considering top coats of lacquer or PPG Porter Glyptex Enamel.

This is the sealer many seem to use for a lacquer finish.

"Sherwin Williams "Promar" E-Z Sanding Lacquer Searler B44FT8"

I called SW and was bounced all over the place trying to figure out what this stuff is and what it's called in Canada. It seems it's a regional product or something.

[bmaupin]

I use thinned fiberglass resin for sealing mdf. I have not used anything else that sealed end "grain" as well and kept seams from showing. I thin the resin with styrene (what resin contains) and not acetone like many others do. My preferred paint is PPG Delstar enamel and it goes on right over top of the resin w/o need for primer, but primer is handy for filling sanding scratches as the fiberglass resin is a little hard to sand.

[Bear]

Beautiful paint job!

[Dennis H]

Whichever brand of lacquer you choose, they should have a matching sanding sealer. It's basically just a softer lacquer so it's easier to sand than the finish coats.

[Solid-State]

Thanks for the fast response guys!! WOW I'll add fiberglass resin to the hat! LOL and fantastic results bmaupin!

I'll post this question I made in another forum...

I thinking of putting together a FAQ on MDF gluing, priming painting etc etc because I've sure found a hodgepodge of info and ideas on the ideal way to work with this material.

I'm curious as to what products to use working with MDF. What is the best glue to use to bind joints. Should I use a biscuit? How should I prep the MDF at the joint. Sand it? As for glues for veneer the local hardwoods shop said use epoxy. I mentioned the iron on glue stuff DIY seem to use but he had no idea what I was talking about and said "no no use epoxy" but this guy knows nothing about MDF substrate. I have heard so many varying opinions on the topic that I'm rather lost as to how to finish the cabs LOL. It seems very little is known in the wood working community how to work with MDF and they all stick their noses up and use baltic birtch. I found some great posts on the shop bot forum regarding working with MDF.

http://www.talkshopbot.com/forum/showthread.php?t=9830

http://www.talkshopbot.com/forum/showthread.php?t=8334#POST68351

And this is an interesting post

http://www.contractortalk.com/f8/has-anyone-ever-heard-using-lacquer-primer-19412/

"Sherwin Williams "Promar" E-Z Sanding Lacquer Searler B44FT8" seems to be popular as a sealer but I don't know how to source it in Canada.

This stuff I can easily source.

http://www.plastikote.com/products/Primer/Sandable-Primer.html

And this looks like a potential FANTASTIC sealer for MDF

http://www.smithandcompany.org/mwp/index.html

They also make a glue in which the marketing material specifically mentions speaker cabinets.

http://www.star-distributing.com/smith/differences.html

Looks like great product.

bmaupin how would you compare PPG Delstar enamel to PPG Porter Glyptex Enamel ?

[Bear]

Add this to the thread list:

http://www.htguide.com/forum/showthread.php4?t=32292

[Solid-State]

Whichever brand of lacquer you choose, they should have a matching sanding sealer. It's basically just a softer lacquer so it's easier to sand than the finish coats.

At this point I'm thinking of avoiding lacquer entirely and using the Smith and Co. CPES/"MultiWoodPrime™" with PPG Porter Glyptex Enamel with no primer just the CPES sealer that also acts like a clear primer. Though the link with the painter ranting about the trim finish work http://tinyurl.com/26thtb2 mentions the undercoat for the Glyptex was lacquer. I assume for the lacquer he's talking about a "sanding sealer" lacquer like Sherwin Williams "Promar" E-Z Sanding Lacquer Searler B44FT8. I tried to talk with SW about that product but I got the run around and was send between departments/divisions over and over again. I was told due to new air quality standards that a lot of these products might not be available in the future

From my research it seems to me, and this opinion is with zero experience, that the CPES "MultiWoodPrime" is the ideal sealant for MDF and the Smith&Co Tropical Hardwood Epoxy and the All Wood Glue is perfect to glue all the cabinet joints. From this point forward I'm rather lost LOL... Do I need a primer over the sealer? That stuff is supposed to work fantastic as a primer as well when using oil. For Latex they say to use a primer over the CPES. If I was to use Glyptex over the CPES due to the fact the CPES primer/sealer is clear I would require multiple coats. Is it possible to use multiple coats and sanding with a alkyd enamels like Glyptex in the first place?

[Lurkalot]

MDF, particularly the edges, is so porous that I have found it difficult to impossible to effectively cover using conventiional sealers. Lacquer based sanding sealers have a higher solids content than the topcoats, but are still relatively low; without applying many coats you will see the end grain through the top coats.

Too address this problem, I mask off the flat surfaces and apply three coats of West System #207 Epoxy. I block sand between each coat, and end up with a well-sealed surface that will accept paint in a fashion similar to the other surfaces, so the finished paint surface is uniform in look and sheen.

Just one solution I know, but it works.

[JonP]

I've had good results with shellac based sanding sealer, specifically Zinnser's Seal Coat. Make sure it's not old, they print the manufacture date on the can. Supposed to be good up to 2-3 yrs, but younger the better. I thin it 50:50 with denatured alcohol, and slather it on till the MDF stops drinking it up. Give special attention to the edges. Wait 15-30 minutes or so, soak away with another coat. After 3-4, you get to diminishing returns, then let it dry for a day or longer and sand it out. Want it even heavier, do the last couple with full strength from the can.

Thinned out like that, it soaks in pretty deep, and with multiple coats, eventually puts a fair amount of solids in there. The alcohol evaporates pretty quickly, too. Waiting longer (a week or more?) so all the solvent can escape, probably helps with dimensional stability. Shellac is compatible with virtually everything, so no problems with the next primer or paint types. It's relatively cheap, too...

The West System Epoxy would probably be the most solid method, but if you're not up to the investment, a heavy shellacing might give give you a decent result.

[PMazz]

I used to use slightly watered down wood filler, applied with a sponge. Let dry, sand and forget. Lately I find it easier and quicker to use the "lightweight" joint compound AKA spackle. They sell the same stuff in small containers usually branded for spot wall patch.

I've used commercial sealers and they just don't cut it with MDF.

[jbateman]

At the ML Campbell site, the "Find a Distributor" link shows Canadian distributors.

Their Clawlock Primer http://www.mlcampbell.com/products/c...rsundercoaters is intended for MDF. You add a 10% catalyst, spray the MDF, sand, spray again, then move on to your topcoart.

Their "Level Primer" is supposed to be better still, though I've not used it.
Neither of these will prevent butt joints from showing through as the mdf shrinks and expands with humidity changes, though.

[Solid-State]

Well I just finished a call with Smith and Co. Acording to Smith and Co they supply their sealant and glue to "more than one" major speaker manufacturer! Also they use it for large PA projects and he mentioned work for Disney etc. When asked about how well the glue works he said, "if it can hold a 50' wooden boat together" LOL. Also it's 100% compatible with all MDF they have used.

Apparently the MultiWoodPime/CPES can take two coats with sanding in between and create a surface he believes even surpasses three coasts of sanding lacquer. These were his major points in painting MDF using their sealant.

1. sand ALL SURFACES of the MDF to remove any factory sealant (VERY VERY IMPORTANT) starting at 180 on the edges/cuts and working to 300 on the whole thing. And vacuum any dust off of the surface.

2. Apply CPES/MultiWoodPrime to all surfaces except joints where O&T Epoxy (low temp cure) or Tropical Hardwood Epoxy (higher temp longer cure) is to be used.

3. wait 2 days for full cure and light sand 300g

4. Apply second coat of CPES/MultiWoodPrime and wait one day for partial cure. When applying paint when it's in this state it will actually bond the paint in a way no other product can compare! (paraphrasing here guys LOL)

5. Apply oil/alkyd based paint or lacquer etc. If using a latex best to apply a primer for it as second coat as some latex stuff can have issues with CPES/MWP. Test first.

The most important thing he believed is to get all the factory sealant/wax or what ever off the MDF so it's down to a 250-300g bare surface and to use their sealant. If this is done he claimed you can paint just about anything to MDF.

Again it's worth noting some major LBE, integrators and manufacturers in the pro/consumer AV world use this stuff when working with MDF.

I asked about a volume purchase for DIY community and he said call me if you work something out!

I emailed Jon Marsh about it as they spoke of this stuff in a thread last year I believe.

This is my first build so I'm a total newbie here but I'm a neurotic about researching everything and doing it right the first time and I've hear a lot of different ideas about working with MDF.

Thanks everyone for sharing your experience and advice! It's very much appreciated.

[orbifold]

Interestingly enough, I go old school with shellac for a sealer. No special sanding on the edges, really. But I do spray the edges a lot more. Since shellac does sink in, I just keep sanding and spraying till it's hard and smooth.
What I do now though, is to use--shameless plug--Target Coatings Inc. water based EM6000 laquer. I find it's great and can be polished, toned with Trans Tint, or even made opaque in your choice of color with Mixol tints.
There is a 9000 grade that has some polycarbonate for hardness, but I have not used it yet. As long as the shellac is a recent buy, it can be from a can from HD. You would of course sand with appropriate grit to tooth it before color/top coat. Haven't had a problem with this.
On TCI's site there is a pretty good forum for questions. No more buying Laq thinner--BIG benny:B:B

[Ezcl]

I've heard of a few different methods while browsing around here and over on AVS...
One is 1/2 wood glue, 1/2 water, and just painting a few coats onto the edges of MDF. It's supposed to be very easy to sand, and hard enough to seal up the edges so that paint won't soak in.

Another method, and the one that I'll be doing, is using Bondo (two part automotive putty). It's probably overkill and more difficult than the wood glue/water method, but I say there's no kill like overkill.

[tylerdurden]

I have had great results with oil based ZAP super stain blocker/primer.
Its a sealer made for blocking stains and odors. Sands great and is tintable.





Lately I have been avoiding butt joints or the like that leaves end grain exposed. I use only corner lock bits for 45 degree panel joints.
like this one....

http://www.grizzly.com/products/Super-Duty-Corner-Lock-Miter-Bit-1-2-Shank/C1712Z

[Dennis H]

Dang, Tyler, that's some impressive glossy black! I shudder to think how much sanding you did to get it that good. :T

[tylerdurden]

Dang, Tyler, that's some impressive glossy black! I shudder to think how much sanding you did to get it that good. :T

Lots and lots!! all the way to 2500 grit. 8O :B