Do I need primer after skim coat

Discussion in 'Walls and Ceilings' started by tractng, Jan 17, 2010.

  1. Jan 17, 2010 #1

    tractng

    tractng

    tractng

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    Hey,

    Just spent the last 2 weeks skim coating my ceiling after the popcorn removal.

    Do I need to primer before paint. It looks like the ceiling is smooth enough that I don't need to texture it (but I like to keep the option open). I prefer smooth ceiling :).


    Tony
     
  2. Jan 18, 2010 #2

    Nestor_Kelebay

    Nestor_Kelebay

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    I would prime before painting.

    But, before you do that, you should check the ceiling by shining a bright light on it at a sharp angle to the ceiling. The sharp lighting angle will make any little bumps and ridges stand out like mountains, making them easy to find. Scrape them off with a tungsten carbide paint scraper (which are sharp enough to easily scrape off texture, but not sharp enough to damage plaster or drywall unintentionally).

    PS: (you don't need to know the rest)

    Most latex and oil based primers will call themselves "Primer/Sealer"s. The reason why is because in your case, you don't really need a primer, you need a sealer. A primer is a coating that not only sticks well to the substrate, but improves the adhesion of the top coat. A sealer is something that prevents fluid (gas or liquid) movement into or out of the substrate. In paints, both of these functions are accomplished by "extender pigments" which are huge rocks that are almost large enough to see with the naked eye. As the primer is drawn into the porous surface of the substrate by capillary action, it's those huge rocks that plug up the porous surface of the substrate (sealing). Those very same rocks are what cause the primer to dry to a rough surface, thereby providing "tooth" for better adhesion of the top coat (priming).

    Since those huge rocks do both jobs in both latex and oil based primers, most primers call themselves "Primer/Sealer"s. Grout sealers, for example, don't have big rocks in them that cause them to dry to a matte finish unless they are advertised as Matte Sealers. If they are advertised as drying to a matte finish, it's because they do have those big rocks in them. They're still not primers because the purpose of them rocks causing the sealer to dry rough is NOT to improve adhesion of a subsequent top coat, it's purely esthetic. There's no top coat in the game plan.

    Hope this helps.
     
    Last edited: Jan 18, 2010
  3. Jan 18, 2010 #3

    tractng

    tractng

    tractng

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    Man do you have a PhD on this topic :).

    I bought the Killz2
    Shop KILZ 5 Gal. White Pigmented Interior/Exterior Water-Based Sealer-Primer-Stainblocker at Lowes.com


    I normally don't use primer but since I have put so much effort into this job, I figure I might as well.




    Tony
     
    Last edited: Jan 19, 2010
  4. Jan 18, 2010 #4

    Nestor_Kelebay

    Nestor_Kelebay

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    Tony:

    I've heard some people that used KILZ 2 weren't too happy with it, but I've never used the stuff myself, so I don't want to dis it.

    For a job like this, you don't need anything special. Any general purpose (also called "PVA") latex primer would be fine.
     
    Last edited: Jan 18, 2010
  5. Jan 19, 2010 #5

    bret

    bret

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  6. Jan 19, 2010 #6

    GBR

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    A.2.3 A drywall primer compatible with the texture material
    shall be applied prior to the application of any water-based
    texture.
    A.4.3 Gypsum panel product surfaces shall be primed prior
    to decoration.
    A.4.3.1 Gypsum panel product surfaces to be painted or textured
    shall be primed with a drywall primer compatible with
    the final decoration.
    A.4.3.2 Where paint materials are to be applied with an airless
    sprayer, the sprayer manufacturer's and paint product
    manufacturer's specifications for proper spray tip, application,
    etc., shall be followed. Sprayed surfaces shall be back-rolled
    for best results.
    A.4.3.3 Wall covering shall not be applied to gypsum panel
    products without first sealing the surface and allowing the
    sealant to dry completely.
    From: http://www.gypsum.org/pdf/GA-216-07.pdf

    Be safe, Gary
     

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