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Thread: Painting large MDF bookcase/shelving system with latex

  1. #1

    Painting large MDF bookcase/shelving system with latex

    I am finishing a large, still unassembled custom-made bookcase (16x9feet, 100+shelves) made of MDF. My idea is to have a smooth semi-gloss finish that is resistant enough to hold books without paint peeling/sticking. I prefer to finish it while it’s still unassembled. Since I have a number of time/space constraints, I decided to go for latex enamel from Duron, even though I am aware oil-based would have been probably better. I have done and plan to do the following, which may have included some mistakes – I wonder whether my plan was/is appropriate

    A) I used Duron acrylic undercoater to prime. Since rolling the primer left roughness, I decided to thin the primer with water (following but perhaps exceeding a tiny little bit the manufacturer’s recommendation) and applying it with a rug. I put a very fine coat of primer (kind of a “wash” of primer, with the MDF color still visible underneath. Hopefully I won’t get adhesion problems.

    B) I got Duron “Plastic Kote” acrylic enamel, semi-gloss, ultra-white. Only after buying the non-returnable paint did I read that the product is “suitable for cabinets and shelving, but alkyd paint or Duron “Signature Select” generally perform better.” So I guess my choice was good but not the best. I have already applied 2 coats of the Plastic Kote paint (which looks very good), and I am not planning to mix products and apply subsequent coats of a different product (unless strongly suggested). I am sanding between coats to get a smooth finish, up to 220 grit (final coat will be sanded to 320 grit). I apply the paint with a brush and 1/4” nap roll.

    C) As I said, I have applied 2 coats of white paint. I will apply a third coat with a little bit of latex extender, as to make it more fluid and as smooth as possible. Some shelves and some edges will be painted in pastel colors. (I am going to tint the white paint with either a bit of acrylic artist paint or a bit of dry pigment).

    My questions are:

    1) Although it’s too late to change now, was it OK to use water-based products for a shelving system/bookcase? It’s not going to be a heavily-used piece (it’s not like kitchen cabinets), and the shelves will not be adjusted that frequently. However, I have heard that professionals strongly suggest using oil-based paint.

    2) As I said I am planning 3 coats. I am planning to sand a bit between coats and at the end to have a very smooth surface. Is that OK?

    3) In order to make the semi-gloss latex enamel more like a lacquery oil-based enamel paint, would it be a good idea to mix some high-gloss latex based enamel (that does look and feel like a lacquery paint) with the third coat of my semi-gloss paint?

    4) I know that latex paint “sticks”. I have been testing the paint by placing heavy books in a painted shelf ‘sample” that has all the coats of paint. So far, they don’t stick. However, in order to add protection to it, and avoid “stickiness”, would it be a good idea to also put some water-based POLYurethane?? I have heard that there could be problems in the poly chips – a future touch-up would be much more difficult. Therefore, and in order not to add too much thickness, I was panning to add just one very thin coat, applied with a rag, just to “seal” the open pores of the paint. Would that be OK?

    5) It’s going to be hard to paint the borders of each shelves with pastel colors without staining some of the white-painted parts of the shelf. Putting masking tape may be too time-consuming. I am planning to again use the latex extender to allow for a quick clean up of colored paint on the white paint. Is that OK?

    Thanks.

    Carlos

  2. #2
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    It's OK to use water borne finishes for projects like this, but latex paint isn't a very good choice, IMHO. Latex paint tends to remain "sticky" when it comes to things you put on the shelving and that can be disheartening. Water borne acrylics (usually applied by spraying) work much better. If that isn't possible, oil-basd enamels will give you a harder finish that stands up to "bookcase" use...once it is fully cured. Full cure of any finish takes several weeks or more and you need to have the patience to not load the shelves until that time passes, no matter what you choose to use for your project.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
    Jim,

    Thank you very much for your reply.
    Would it be then a good idea to put some water-based polyurethane over the semi-gloss latex, for added protection? If so, how long should I wait before applying the poly? Thanks again.

    Carlos

  4. #4
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    You can use just about anything over latex....

    Quote Originally Posted by Carlos Arteta
    Jim,

    Thank you very much for your reply.
    Would it be then a good idea to put some water-based polyurethane over the semi-gloss latex, for added protection? If so, how long should I wait before applying the poly? Thanks again.

    Carlos
    ....but you shoulda used an alkyd primer and finish. Carlos, when I finish MDF, I use joint cement as a filler. I trowel it on using a broad knife and trowel it off clean. It leaves a powdery residue that I sand off with a ROS and 220 paper. One coat of oil primer and two coats of alkyd finish, will make it look like glass. As Becker said, latex will remain tacky, and for years on, your books will tack to the finish. You can use a clear finish over your latex. Wait about a week and recoat. Good luck.
    Phil in Big D
    The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

  5. #5
    Phil,

    Thanks for your reply. I will consider putting poly on the latex after a week. The main frame of the bookcase will have to be assembled by then, though, so I guess I won't be able to poly all the sides. I will be able to poly the adjustable shelves and vertical parts.

    Questions:
    1) How many coats of poly, and how much to wait between then? The intra-sanding should be done with 320 grit?
    2) I have also heard that putting poly may actually make matters worse, as it will add thickness that will leave the bookcase more chip-prone. Is this true? Would this problem outweight the tackiness problem?
    3) Instead of brushing the poly, I was considering wiping it with a cloth, as I think this would lead to the thinnest film. Is this a good idea?

    Thanks again,
    Carlos

  6. #6
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    Putting a "hard" finish over a "soft" finish still leaves you with a "soft" finish, although you have a little more protection. Overcoating the latex paint after it fully cures with a water borne acrylic, including one that contains polyurethane resins will at least help with the "sticking" to some extent.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  7. #7
    Jim,
    Thanks again for your reply.
    Just one clarification: I used an "acrylic latex enamel" from Duron, and it appears to be a good quality product (their technical info say that it's a "premium product... also suitable for cabinets and shelving, although alkid generally perform better.")

    With respect to the "tackiness" problem, Is there a difference between "latex enamel" and "acrylic latex enamel"? I read elsewhere that, while latex always has the tackiness issue, an acrylic latex shouldn't be as big of a problem. The kind replies that you and Phil sent mentioned "latex". Also, your most recent reply said that an "acrylic resin" ameliorates the problem. Therefore, I gather that, since I did use an acrylic resin, my tackiness problem should be less severe than what you and Phil mentioned, which means that I might probably get away by letting the paint fully cure (a month) before loading my books. Thanks.

    Carlos

  8. #8
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    The products you cite are still latex paint. The acrylics I mentioned are not. Examples being Target Coatings USL and Fuhr International 9100. Even Minwax water borne poly...which I will even admit to using on the bookcases I built for our girls' room last year. (I normally don't use anything polyurethane...)
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #9
    Jim,
    Thanks for your reply. I will plan to use Minwax polycrilic over the (third and final coat of) my acrylic latex. Given the size of the bookcase (16 feet by 9 feet: 14 equidistant vertical parts of 9 feet tall each, more than 100 shelves, each of 1 squared feet), I will plan to do the following:
    1) Wait a week after the final coat of acrylic latex.
    2) Lightly sand the shelves.
    3) Apply one coat of Polycrilic to the shelves, either with a rag or a nylon brush.
    4) Wait a month before loading shelves with books.

    I will not apply polycrilic to the vertical parts -- they won't hold books anyway, plus it will be a pain to touch-up if need be. (If I get chips/cracks to the poly on the shelves, it will be very easy to touch-up them, since the shelves are small). Also, I will apply only one coat of polycrilic -- I don't look forward to coating 100+ shelves twice, plus I am not going for appearance, just more protection.

    Does it sound like a reasonable plan? Does applying the poly with a rag sound weird? Will just one coat of poly be insufficient, and a second coat will be necessary?

    Thanks again.

  10. #10
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    Carlos, it takes a lot longer than a week for the latex paint (especially the thicker enamel) to fully cure...
    --

    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
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    Yes,

    Quote Originally Posted by Jim Becker
    Putting a "hard" finish over a "soft" finish still leaves you with a "soft" finish, although you have a little more protection. Overcoating the latex paint after it fully cures with a water borne acrylic, including one that contains polyurethane resins will at least help with the "sticking" to some extent.
    ...and that's about all you can expect at this point. You haven't ruined anything, Carlos. I doubt the bookcase will take much abuse.
    Phil in Big D
    The only difference between a taxidermist and the taxman, is that the taxidermist leaves the skin. Mark Twain

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