# Primer / Sealer VS Flat paint



## A+ Texture (Sep 23, 2008)

Hey guys, I'm a drywall guy by trade and I was wondering... Whats the difference between a flat paint and a primer sealer like killz. I've noticed doing many repairs that when shooting texture, walls with flat paint will absorb the moisture but walls with semi-gloss the glossy paint acts sort of like a vapor barrier, meaning the wall will not absorb the moisture anywhere near as fast. So even though killz is usually flat does it act like more of a semi gloss. The reason I'm asking is because when removing popcorn or rocking a garage with no insulation semi-gloss seems to be king and I'm wondering if a killz type product is just as good. I hope what I'm asking is clear and thanks a lot. Let me know if i need to elaborate more.


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## nEighter (Nov 24, 2008)

I don't know what you are asking specifically. You start out asking about flat and speak about it absorbing water quicker than any of the other finishes, then you move into talking about vapor barriers and kilz and a garage with no insulation. What do you want to know exactly? You got a job painting a garage and want to know what paint to use?


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## A+ Texture (Sep 23, 2008)

Sorry for not being more clear. I'm just wondering what does a primer/sealer like killz do that a flat paint does not? The reason I went into the garage thing is, I've seen a few threads about uninsulated garages being painted with flat paint and cracks coming back, but ones painted with a semigloss don't crack because the semigloss doesn't allow the rock to constantly absorb the ambient moisture and then dry out causing it to swell and shrink constantly. Thats what I meant by it being like a vapor barrier.


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## Mr. Mike (Dec 27, 2008)

> I'm just wondering what does a primer/sealer like killz do that a flat paint does not?


If I am painting an area of new drywall and the desired finish is to be a satin or higher sheen I will use a primer product, if the walls are eggshell I will use a self priming eggshell paint, if the walls are going to be flat I use the self priming flat.

Kilz will only be used on my jobs if there is water, and fire damage or some residue like glue or food or even but not limited to pet urine on the walls.

I have seen eggshell and satin come off the walls like you described though and most of the time this is all due to painting the garage while it is freezing cold out side, but the job has to be done, one more reason I don't do new houses per say.


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## woodworkbykirk (Sep 17, 2008)

on a similar note, a painter i know uses bin primer for mdf. last time i worked with him on a project i needed some to touch up a few jamb extensions on windows before installing. i noticed the primer almost smoothed out the rough texture of the mdf as opposed to making it more prounounced. is this a specific type of bin primer or is it cut down or something? im doing a project right now where all the mdf has a routed profile on it and im looking to minimize sanding before priming


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## Faron79 (Nov 29, 2007)

> walls with flat paint will absorb the moisture but walls with semi-gloss the glossy paint acts sort of like a vapor barrier, meaning the wall will not absorb the moisture


You answered your question with the above sentence!

Paints & Primers are TWO DIFFERENT THINGS!
* Primers are RESIN-rich...PAINTS are PIGMENT-rich.
* Primers will largely prevent moisture from absorbing into a substrate like wood or drywall.
* A cheaper Flat paint is fairly porous, and SHOULDN'T be used as a primer. It's porous because, to appear "Flat", the pigments are "coarser". This scatters light reflection in a non-uniform pattern, thereby appearing "Flat".
* Glossier paints, like S/Gloss, have a smoother "Binder-resin", and finer-ground pigments. This "smoother" film is MUCH more resistant to moisture penetration than a Flat. Relative to a Flat, Glossier paints have a little less pigment too.
* Because it's a smoother/tighter film, glossier paints resist moisture the best, AND appear glossy because they reflect light UNIFORMLY.

Primers are SOOOOO important because they prevent the moisture & binder-resins from the PAINT from soaking into the sheetrock.
>>> NOT priming is the main reason for sheen-variation in paints. The thirsty areas will suck in more paint, therefore making the paint "duller" than it should be.
>>> A GOOD primer helps the paint develope its' gloss ON TOP OF the substrate.
>>> A Flat PAINT will NOT prevent much absorption into itself.
>>> PRIMER'S main job is for ADHESION of the topcoats of paint. The secondary benefit is for even sheen-developement.

DON'T fall into the "Hack" view of "Flat paint is as good as a primer..."
>>> It's flat-out WRONG.

Faron


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## chris n (Oct 14, 2003)

Mr Mike says that Kilz is used to cover" some residue like glue "

which it is NOT labeled for. Just another rip off scheme from the master closer


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## Mr. Mike (Dec 27, 2008)

Glue residue is left n the wall after wallpaper removal, if you don't kilz it then what Mr. Chris n?


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## Frankawitz (Jun 17, 2006)

Faron,:thumbsup:
You hit the nail on the head. Primer is a sealer. paint is a Decorative coating the primer will be drawn into the sheetrock or wood, paint lays on top of the sheetrock or wood. the only paint that I know of that is self priming is Benjamin Moore's Iron Clad. When I do repairs I use Block Filler for two reasons one it soaks into the repairs and being that it's like Marshmellow fluff it puts a nice stipple to the repair so it will blend in better when the finish paint is applied.



www.frankawitz.net


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## A+ Texture (Sep 23, 2008)

Thanks fellas, I'll be doing a big popcorn removal job and was concerned about the type of paint to use. My first popcorn job I did years ago (my own house) I was just learning. The rooms painted with semigloss or eggshell never cracked, the one done with cheap flat paint did. Thats what I get for not priming first. Anyway I was planning on tinting a primer and leaving that as a final coat for customer, I just wanted to make sure that the primer/sealer does in fact act more like a semi gloss. But I suppose using a self priming flat paint would be just as good.


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## chris n (Oct 14, 2003)

Glue residue is left n the wall after wallpaper removal, if you don't kilz it then what Mr. Chris n?


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## chris n (Oct 14, 2003)

Glue residue is left n the wall after wallpaper removal, if you don't kilz it then what Mr. Chris n? 

Or better yet


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## chris n (Oct 14, 2003)

Anyway I was planning on tinting a primer and leaving that as a final coat for customer,

Is the customer paying for a primer or a finish coat, or both?If it was me I would do both, no matter what.


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## A+ Texture (Sep 23, 2008)

chris n said:


> Anyway I was planning on tinting a primer and leaving that as a final coat for customer,
> 
> Is the customer paying for a primer or a finish coat, or both?If it was me I would do both, no matter what.


 Well I'm charging for the primer. I was thinking a five gallon bucket, which would be more than enough and then give everything another dusting using the rest of the bucket. If people paint ceilings with flat and primer is flat is there any reason not to use two coats of primer or a self priming paint? I do want to do the job right and I want a happy customer. Do you think it would be better to use a primer and then a seperate paint for finish coat? Thanks.


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## chris n (Oct 14, 2003)

Do you think it would be better to use a primer and then a seperate paint for finish coat? 


This is the norm, unless you are the famous Jack Paul:whistling


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## deach (May 11, 2008)

chris n said:


> Do you think it would be better to use a primer and then a seperate paint for finish coat?



In a word, YES.


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## MarcP (Jan 29, 2007)

woodworkbykirk said:


> on a similar note, a painter i know uses bin primer for mdf. last time i worked with him on a project i needed some to touch up a few jamb extensions on windows before installing. i noticed the primer almost smoothed out the rough texture of the mdf as opposed to making it more prounounced. is this a specific type of bin primer or is it cut down or something? im doing a project right now where all the mdf has a routed profile on it and im looking to minimize sanding before priming


Use BIN pigmented white shelac. It works great for that purpose.


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## ClosetPro (Apr 29, 2009)

woodworkbykirk said:


> on a similar note, a painter i know uses bin primer for mdf. last time i worked with him on a project i needed some to touch up a few jamb extensions on windows before installing. i noticed the primer almost smoothed out the rough texture of the mdf as opposed to making it more prounounced. is this a specific type of bin primer or is it cut down or something? im doing a project right now where all the mdf has a routed profile on it and im looking to minimize sanding before priming


Always plan on a second coat for the edges of MDF or "pre address" the edges of MDF before your final coat.


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## chris n (Oct 14, 2003)

What? No witty comeback from MR Mike about the proper procedure to paint residual PASTE( not glue)?:w00t:


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## We Fix Houses (Aug 15, 2007)

While were on this, remind me of (for drywall):

Proper primer for popcorn removed skimmed out smooth ceiling.

Proper primer to use before reapplying popcorn to the ceiling again.


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