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  • Painting MDF

    I'm in the process of gluing up 7 MDF 5-panel doors to replace those in the bathrooms. Some of the copes do not line up exactly, so some sanding is in order. I'm using 180 and finishing with 220 grit paper. Is there any need to go finer?

    As the for the paint, I'm planning on using a water-based primer and taking off the raised grain with 150 or 180 paper. Any need to go finer? Finish coat will be a latex semi-gloss enamel, likely sprayed with a HLVP gun. Any suggestions as to number of coats, sanding between coats, etc?


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  • #2

    Re: Painting MDF

    Re: Painting MDF

    I hope someone with first-hand knowledge will chime in here, because I'd be concerned about a water-based primer on MDF without some kind of sealer. MDF is really sensitive to moisture and the surface degrades very quickly. (Wipe a piece of scrap with a moist cloth and you'll see what I mean.)

    It might well be okay, but unless someone here who has done what you're proposing says it is, I suggest you ask a paint-store "pro" whose advice you trust before spraying.

    Cheers, Garrett

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    • #3

      Re: Painting MDF

      Re: Painting MDF

      I've done about 300 feet of baseboard using the method described above, however the quality of the finish was not as critical as the doors will be. Primed, 105 paper to knock off the raised grain and about 3-5 coats of latex enamel. Since you are looking at baseboards from more than 5 feet away, any imperfections are pretty much invisible. The cabinet and vanity doors are seen from much closer.

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      • #4

        Re: Painting MDF

        Re: Painting MDF

        I've done it....try and avoid water based primer, I used it when I started doing some new doors for my kitchen but switched to oil once I saw how rough it got, big headache. Save yourself a lot of work and stick to the oil if you can stand the smell.



        Hope this helps,

        KenR


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        • #5

          Re: Painting MDF

          Re: Painting MDF

          I find that 2 coats of melamine over an alkyd base works realy well on MDF.

          To be able to sand out properly between coats, you will need to wait several days for the paint to harden, particularly for the primer.

          I use an inexpensive foam roller from CTC to apply the paint which leaves a slightly pebbled surface but not flat in sheen.

          After 30 days you have a surface that will stand up well on frequently used doors such as vanities.

          If you're in a hurry, you'll want to use a latex enamel, but it's nowhere near as durable a surface as alkyd/ melamine (and don't let the paint store clerk tell you that it is.) In my experience the first time someone hits the latex paint with the plug of a dryer cord, you'll have a chip.


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          • #6

            Re: Painting MDF

            Re: Painting MDF

            Hi Ken

            The best 'cure' that I know for neutralizing the smell of oil based paint is to cut onions in half and place them in the room with the smell. If you were painting a room then half a dozen onions cut in half works perfectly - and no smell!!

            My two cents!,

            Regards, Ron

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            • #7

              Re: Painting MDF

              Re: Painting MDF

              Jack-- I use a product called Quick dry Plastic primer from General Paint and it works great. I put lacquer over it but also have used quick dry enamel and semi-gloss enamel over it. You also might be able to use an acrilic latex over it if you ask.
              Cheers Wally!!

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              • #8

                Re: Painting MDF

                Re: Painting MDF

                Hey stranger,

                My paint guy got me onto CIL latex primer and Para latex paint for all my LDF and MDF projects. Works great. Two coats of primer, light 220 hand sanding after each usually 3 on edges. If you want to see the results drop in on the way to the cottage.

                Gump


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                • #9

                  Re: Painting MDF

                  Re: Painting MDF

                  Garrett, I understand the issue you are describing. In my case it was not a problem. I built a cabinet to mount on the wall over the toilet. It's built from 5/8" MDF. I primed it with latex primer and finished it with latex semi-gloss.

                  Here's my experience with that cupboard this past winter to give you an idea of the integrity of the MDF after this paint job and a year and a half of showers, baths, etc. We renovated the bathroom in March, including new paint on the walls. We were trying to decide whether to mask the cabinet and paint around it or take it down and paint the whole wall. We decided it would be easier to take it down.

                  I removed the four screws that hold it on the wall and my wife braced herself to take the weight of the cupboard. Except it didn't come off. That puppy is stuck so solidly to the wall that it wouldn't budge, even when I gave it a couple of pretty hearty tugs. So not wanting to rip the facing paper off the drywall I put the screws back in and got out the masking tape.

                  Obviously the paint had not cured completely before I screwed the cupboard to the wall. And equally obviously the painted surface of the MDF had maintained its integrity.

                  Just one person's experience.


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                  • #10

                    Re: Painting MDF

                    Re: Painting MDF

                    I have used Melamine in the bathroom, yes, it must cure properly, I had a large 4 shelf unit of 1/2 MDF I put primer and then a coat of melamine, stick to the floor because I was in a hurry and put the shelf in place only about 12 hours after I painted it. I have an over the toilet shelf unit and a wall mounted shelf unit (bathroom had nothing before) that I used melamine and primer, not complaints, no chips, no scratches.

                    I have used primer and two coats of tremclad on top of a workbench I made from MDF in the shop, no scratches or chips and that work bench is for the mitre saw, drill press (bench top) and belt/disc sander. I am really happy with that.

                    Don't use cheap rollers to put on either, I too had the pebbling effect on a craft display table I made for the SWMBO, required a good sanding (approx 30sqft) and a repaint with a high quality roller.


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                    • #11

                      Re: Painting MDF

                      Re: Painting MDF

                      Finished assembling and sanding the seven doors today. Wife came home yesterday with a CIL latex primer and a 100% acrylic paint for the whole bathroom (really looking forward to that) .

                      Even with the latex needle for the sprayer, I had to thin the primer quite a bit to get an even coat. They are all primed now and will sit until next weekend before the finish coat(s) go on.

                      Thanks for all the advice. TTFN


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