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Thread: Non Traditional build Finishing MDF

  1. #1
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    Non Traditional build Finishing MDF

    Been a while since I posted, life takes a lot of turns 😊 I am involved in a non-traditional furniture build, which deviates from my area of comfort (Arts and Crafts White Oak). It is cabinets for a Loudspeaker system. It is constructed of MDF. I have done a few speakers builds in the past for myself and others, but always used veneers which allowed for traditional finishing techniques. However, this is not practical in this project due to some portions of the cabinets being sharply curved (inner), so I decided to do the project finish with enamel. I did this once years ago and had issues with differing porosity between the MDF edges, routed portions and face and was not happy with the outcome. So, I want to seal the entire surface, but especially the porous portions before I spray so the finish will be uniform. I am hoping someone can help, any thoughts?

  2. #2
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    Several options to seal the cut edges of MDF. Drywall compound (seriously, it works great), or high build primer. Probably others. In any case, use a primer after whatever you use to seal the edges, and make sure it looks consistent with the uncut surfaces before spraying the finish coats. Better to apply and sand an extra coat of primer.

    John

  3. #3
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    John, I see primers at the store. How do I determine if it is High Yield? Is that a solids content indication?

  4. #4
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    Quote Originally Posted by Paul Canaris View Post
    John, I see primers at the store. How do I determine if it is High Yield? Is that a solids content indication?

    High build. Go to SW's, BM's, etc. They'll be able to recommend the right products. l

    John

  5. #5
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    For something with a lot of finished edges on MDF, it's better to buy MDF designed machined edges. You won't find it in the box stores, but usually any large city will have a supplier that also sells good grades of plywood.

  6. #6
    I've used both drywall compound and automotive glazing putty (designed to fill pin holes and scratches) for similar things in the past.
    ~mike

    scope creep

  7. #7
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    I recently watched a video on Youtube comparing all of these home-brew solutions like drywall compound, PVA glue, and several others for sealing edges. In the end, they were all the same, and primer was the easiest one to deal with. I've built several speaker boxes, just sprayed them with primer, and then paint. I've tried brushing on a coat on the "end grain" and not, without any real difference. I have found that sanding the edge makes a better result, otherwise you're looking at a texture difference. High build primer, or surfacer, would help a lot here. I did one with surfacer and then catalyzed auto paint which was just as glossy as metal.

  8. #8
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    No idea what SW or BM's are.

  9. #9
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    Sherwin Williams. Benjamin Moore.

    John

  10. #10
    Quote Originally Posted by Carlos Alvarez View Post
    I recently watched a video on Youtube comparing all of these home-brew solutions like drywall compound, PVA glue, and several others for sealing edges. In the end, they were all the same, and primer was the easiest one to deal with. I've built several speaker boxes, just sprayed them with primer, and then paint. I've tried brushing on a coat on the "end grain" and not, without any real difference. I have found that sanding the edge makes a better result, otherwise you're looking at a texture difference. High build primer, or surfacer, would help a lot here. I did one with surfacer and then catalyzed auto paint which was just as glossy as metal.
    My experience is about the same as yours. I have had good results from Zinsser BIN primer, available at any Home Depot. I think it is an advantage that it is shellac based, not water based. I don't like using any water based products on raw MDF.

    I don't know if you've already purchased your material, but if not, it may be good to know that all MDF is not created equal. The MDF from a professional lumber supplier will generally be better than a home center. Also there are premium high density brands of MDF. The one I have used is called Plum Creek. It routs extremely well, and the edges are not nearly as porous as home center MDF, probably due to the density. If you go with a high grade MDF like Plum Creek and prime with BIN, you will be happy with the results.

    Otherwise, using BIN on any MDF will work, but you might need to sand back and do a second coat to get to the finish line.

    Edwin

  11. #11
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    +1 on shellac based BIN primer. Fast drying, no grain raising or swelling on MDF. You do have to work quickly. It comes white but you can tint it if you’re using a darker paint color. I like to leave some contrast so I can identify areas I missed.

  12. #12
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    Thank you to all who have responded. I can now get going. Very appreciated.

  13. #13
    I've used this SW product and had great results. I sprayed it on poplar with an airless set-up.

    https://www.sherwin-williams.com/hom...ll-wood-primer

  14. #14
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    This is the type of MDF I was talking about. I don't know if it's typically called Double-Refined, or Ultra-Refined. That may just be that particular brands designation. I just ask my plywood supplier for what I need. It's well worth the extra cost if you have many feet of edges to smooth.

    http://packardforestproducts.com/pro...refined-mdf-2/

  15. #15
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    I still can't find that, or other great processed products locally. Not even sure how to search. Lumber yards seem to have the same old stuff without any "ultra refined" or anything like that. "It's just normal MDF man."

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