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sealing MDF

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Forum topic by Karda posted 01-20-2021 05:25 AM 405 views 0 times favorited 13 replies Add to Favorites Watch
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Karda

2881 posts in 1560 days


01-20-2021 05:25 AM

I put MDF on a light duty work bench is shellac sufficient to seal it


13 replies so far

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Walker

451 posts in 1479 days


#1 posted 01-20-2021 06:05 AM

yes. Light coats, many coats, sand in between.

-- ~Walker

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Karda

2881 posts in 1560 days


#2 posted 01-20-2021 06:07 AM

ok thanks

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tvrgeek

1388 posts in 2656 days


#3 posted 01-20-2021 11:47 AM

Sealing MDF is a common topic on the speaker building forums. Even worse is preventing glue lines from sinking in after time. The very best sealer I found is polyester resin as used for fiberglass. Two coats. For the glue line, switching to powered resin solves that, but of course, not a work bench issue.

Personally, I like to make my top out of the Melamine covered MDF. Cleans up easy, nice and bright. Most paint or clue pops off, oil and other stuff wipes up. So, bottom layer either 3/4 PB and then 3/4 top, or 2-by lumber with top.

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Karda

2881 posts in 1560 days


#4 posted 01-20-2021 05:20 PM

ok thanks

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woodbutcherbynight

7703 posts in 3416 days


#5 posted 01-20-2021 05:32 PM

You can, takes time. To me it is weak link in the chain. For my benches I edge band with oak and cover with Formica.

-- Live to tell the stories, they sound better that way.

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Walker

451 posts in 1479 days


#6 posted 01-20-2021 06:12 PM

another popular option is to plunk down a sheet of 1/8” or 1/4” tempered hardboard on top of the mdf. Once it gets dinged up, just replace it.

-- ~Walker

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Karda

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#7 posted 01-22-2021 03:14 AM

would a layer of paste wax be out of line, or will it soften the MDF

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Walker

451 posts in 1479 days


#8 posted 01-22-2021 03:20 AM

That’s a good question. I just paste waxed the hardboard top on my bench, it seems fine. Now the sawdust blows right off. MDF could react differently. Why not just test on a scrap piece?

-- ~Walker

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Karda

2881 posts in 1560 days


#9 posted 01-22-2021 03:38 AM

ok thanks

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BurlyBob

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#10 posted 01-22-2021 05:05 AM

After using it in some shop drawer bottoms, I’ve sworn to never use MDF for any thing. It took at least 4 coats of Poly before I could even begin to get a nice finish. That stuff soaks up like a sponge and it’s not very strong. It’s also terribly dusty to work with. I hate it. I may be the odd man out, which isn’t unusual. I’ve got a very pieces left and once they are gone, they’ll be no more in my shop.

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Karda

2881 posts in 1560 days


#11 posted 01-22-2021 05:20 AM

but its just a work bench, and not the primary in this case it will do. its the top has .75 plank underneith

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tvrgeek

1388 posts in 2656 days


#12 posted 01-22-2021 01:05 PM



After using it in some shop drawer bottoms, I ve sworn to never use MDF for any thing. It took at least 4 coats of Poly before I could even begin to get a nice finish. That stuff soaks up like a sponge and it s not very strong. It s also terribly dusty to work with. I hate it. I may be the odd man out, which isn t unusual. I ve got a very pieces left and once they are gone, they ll be no more in my shop.

- BurlyBob

Bob, You just picked the wrong material for your project so I can understand your disappointment. Even hardboard would have been better, but bitch ply is what I consider proper for that. Yes MDF is dusty and it is the super find dust that is very bad for your health. Always use a good mask even with a DC and filters. When I finish an MDF project, I use my leaf blower to get all the dust out of the shop. Then clean all my filters.

Among other things, I build high end loudspeakers. MDF is about as close to perfect a material as anything. Assuming you seal MDF the same way you may seal wood is not a fault of the material. In the speaker hobby, we master MDF. Due to it’s dust, I am upgrading my DC system to a cyclone as a cutting up just one sheet is enough to plug my canister and blow the bag off. Like all materials, they differ and you need to learn how to deal with it.

I do use thinned varnish on MDF, but it is to reinforce the locations for mounting screws. It soaks in mostly from the edges and makes the screw hole much stronger. Saves using Hurricane clips or T nuts. It also helps around recess cutouts to reinforce the sharp edge. Then I use my poly resin.

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Karda

2881 posts in 1560 days


#13 posted 01-22-2021 05:09 PM

MDF like any other building material has its uses and its weaknesses. use MDF for its strengths, use it for MDF not a plywood replacement. I think because of it density it would make a good top and even light duty drawers as long as the design doesn’t require screwing into the edge.

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