How to seal/paint MDF? - Woodworking Talk - Woodworkers Forum

 
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post #1 of 19 Old 12-14-2011, 12:36 PM Thread Starter
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How to seal/paint MDF?

I'm trying to build a desk and am planning on using MDF as the desktop. I know MDF is hard to paint because the edges soak up paint and can also chip off, so what's the best way to seal the edges and paint MDF?

I've spent some time reading about this the past few days and it seems like when using MDF as desktop it needs to be:

1. Sealed
2. Painted
3. Finished

From the reading I did, it seems like many people recommend using Shellac BIN primer to seal, painting with latex paint, then finishing with polycrylic protective finish. Does that sound about right?
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post #2 of 19 Old 12-14-2011, 12:44 PM
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use the thickest primer sealer you can find - i did a sign in mdf for a customer and i had to use spray paint for color match reasons and it took 10-15 coats to seal and to not see the wood grain

Can I build that? There's only one way to find out.

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post #3 of 19 Old 12-14-2011, 01:02 PM Thread Starter
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Hi, thanks for your reply.

I probably should have mentioned that I know absolutely nothing about woodworking, and I don't even really know what primer or finish is (I'm just quoting what I read ). So, if anyone has any suggestions, you'll probably have to be really specific (i.e. product names) in order for me to understand
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post #4 of 19 Old 12-14-2011, 01:49 PM
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Hi Nate: I would recommend laquer sanding sealer, sold at most home stores, you can apply it with brush , roller or an HVLP gun. But you must use precaution, to protect your lungs, if at all possible work out doors. and no open flames allowed! But on the plus side its very forgiving to work with, very fast turn around time depending on your R. humidity. sand with 220 grit between coats, ( 2 is usually OK) dont forget to seal ALL the wood. if you seal one side of a piece of wood and not the other, moisture via humidity will enter the unsealed side and cause it to swell. after that you can paint your wat4er base and the a clear coat! Hope this helps!
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post #5 of 19 Old 12-15-2011, 04:12 PM Thread Starter
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Would a water-based primer like Kilz 2 work as the sealer/primer?
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post #6 of 19 Old 12-15-2011, 05:01 PM
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Originally Posted by Nate View Post
Would a water-based primer like Kilz 2 work as the sealer/primer?
I wouldn't use water base on it, at least not as a sealer. I usually use Zinsser BIN or Zinsser Cover Stain. BIN is available in a aerosol, Cover Stain may also be available in aerosol, haven't looked for that. Automotive aerosol primers work also, Rustoleum, etc. Still liable to get a little fuzz on the edges or machined surfaces but that knocks down with a light sanding after priming.
Glue sizing will also help seal it, about a 50-50 mix of wood glue and water. will need a bit of sanding with that also.

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post #7 of 19 Old 12-15-2011, 05:51 PM
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Quote:
Originally Posted by Nate View Post
Hi, thanks for your reply.

I probably should have mentioned that I know absolutely nothing about woodworking, and I don't even really know what primer or finish is (I'm just quoting what I read ). So, if anyone has any suggestions, you'll probably have to be really specific (i.e. product names) in order for me to understand
If you know absolutely nothing about woodworking, what tools do you have to cut the sheet. Do you have a compressor and spray gun? Do you have any painting experience of any kind?








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post #8 of 19 Old 12-15-2011, 08:05 PM Thread Starter
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I wouldn't use water base on it, at least not as a sealer. I usually use Zinsser BIN or Zinsser Cover Stain.
I went to Lowe's today to get the wood and saw Zinsser BIN there. It's about three times as expensive as the Kilz 2. If that's what I should use I'll go ahead and get it, though

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If you know absolutely nothing about woodworking, what tools do you have to cut the sheet. Do you have a compressor and spray gun? Do you have any painting experience of any kind?
The only tool I have that might have been able to cut it is a jigsaw, so when I was getting the wood at Lowe's I asked them to cut it for me.

No, I don't have a compressor or spray gun. Wouldn't it be OK to just use a paint roller?
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post #9 of 19 Old 12-15-2011, 08:53 PM Thread Starter
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OK, question: Would the oil-based Kilz primer work? The Zinsser BIN primer was a little over $40 if I remember correctly, and I found Kilz Original oil-base primer on the Lowes website for $14.94: http://www.lowes.com/pd_45551-807-10...=#BVRRWidgetID
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post #10 of 19 Old 12-15-2011, 10:56 PM
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I use MDF all the time for fabrication and a relatively cheap method is to seal the edges with thinned white glue. It soaks into the pores but dries clear and provides a good paint surface. You may need a few coats with some light sanding between each, but it'll get the job done. Just add enough water to make it flow from a brush (like the consistency of coffee cream).

Best of luck.
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post #11 of 19 Old 12-15-2011, 11:27 PM
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Originally Posted by Nate View Post
OK, question: Would the oil-based Kilz primer work? The Zinsser BIN primer was a little over $40 if I remember correctly, and I found Kilz Original oil-base primer on the Lowes website for $14.94: http://www.lowes.com/pd_45551-807-10...=#BVRRWidgetID
Hi Nate - I agree, BIN is a bit pricey. I picked up a gallon of the Zinsser Cover stain at Home depot for about $16, I think that's about the same price range as Kilz. Also, a gallon would be overkill big time, quart would be plenty. I don't think you reall need to seal the whole thing, just the edges or where the factory finish has been compromised by sawing, routing, etc. The nice part about BIN and Cover Stain is you can top coat either with just about anything in about an hour.
You can also get rattle cans of BIN for $6-7 around here. Follow the cautions on all that stuff, BIN is especially flammible as it uses alcohol as a solvent. Cleanup for BIN is denatured alcohol or 50-50 ammonia and water. Cleanup for Cover Stain is paint thinner or mineral spirits.

John

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Last edited by jschaben; 12-15-2011 at 11:29 PM.
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post #12 of 19 Old 12-16-2011, 12:10 AM
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Quote:
Originally Posted by benstark View Post
I use MDF all the time for fabrication and a relatively cheap method is to seal the edges with thinned white glue. It soaks into the pores but dries clear and provides a good paint surface. You may need a few coats with some light sanding between each, but it'll get the job done. Just add enough water to make it flow from a brush (like the consistency of coffee cream).

Best of luck.
I've read of using diluted white glue as a sealer before but have never tried it. What ratio do you dilute it?
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post #13 of 19 Old 12-16-2011, 01:59 AM
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Hey Nate, here is a project I did in the past all out of MDF, after working with MDF for awhile I came to the conclusion that car primer works amazing, dries fast goes on thick, and sands really nice once dried, and afterwards you can put what ever you like over it. I've also used something called vinyl sealer which is available at paint stores mainly, also works great. But as most everyone else has said STAY AWAY FROM WATER anything when it comes to primer or your first coat on raw MDF it will give way more work than you could want.....Just my two cents, hope that helps
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post #14 of 19 Old 12-16-2011, 07:40 AM
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Drywall spackle

I have had good luck with using drywall spackle to seal the edges of mdf. Just put it on with a putty knife and sand down to shape. You end up with a great edge.
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post #15 of 19 Old 12-16-2011, 03:53 PM
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I have had good luck with using drywall spackle to seal the edges of mdf. Just put it on with a putty knife and sand down to shape. You end up with a great edge.
that sounds like a lot of work ;-)
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post #16 of 19 Old 12-16-2011, 10:06 PM
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I guess dilute the white glue 10:1 with water ( glue: water).

For a professional finish you can use a primer called Ellis. It's a water based, expanding sand able primer. We used that stuff all the time for MDF for high end projects.

For what you are doing, go for the glue.

As for water... Yes, MDF and water don't mix. But painting it with water based paint is very different than building a pool deck with it.
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post #17 of 19 Old 12-17-2011, 10:43 AM
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I have had good luck with using drywall spackle to seal the edges of mdf. Just put it on with a putty knife and sand down to shape. You end up with a great edge.
do you mean drywall compound?
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post #18 of 19 Old 12-17-2011, 12:15 PM
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Originally Posted by ModCo Design View Post
Hey Nate, here is a project I did in the past all out of MDF, after working with MDF for awhile I came to the conclusion that car primer works amazing, dries fast goes on thick, and sands really nice once dried, and afterwards you can put what ever you like over it. I've also used something called vinyl sealer which is available at paint stores mainly, also works great. But as most everyone else has said STAY AWAY FROM WATER anything when it comes to primer or your first coat on raw MDF it will give way more work than you could want.....Just my two cents, hope that helps
WOW.. it looks awsome. that shiny surface looks almost like melamine. how did you do it? gloss paint over car primer sealing will get me that result??
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post #19 of 19 Old 12-17-2011, 05:54 PM
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Yamster, that's correct...I used a two part car primer and completely sealed all the edges and surfaces, I then lightly sanded the edges and gave them one more coat of primer. After that I wet sanded my surfaces (yup wet sanded), and cleaned it off then applied my finish over that.....I took a few years of schooling in auto customizing and knew that a single coat of car primer could go on as thick as a dime, so I gave it a shot, was thrilled with the results and have used that ever since.....oh and the Sherwin Williams two part kevlar conversion varnish works great too, and dries in less than 15 minutes
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