# Painting shiplap pine semi-gloss white. Should I fill the knots?



## joecaption (Nov 30, 2011)

All depends on the look your going for and what looks good to you.
I would have used Shellac on the knots to stop the bleeding.


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## klaatu (Mar 9, 2015)

joecaption said:


> All depends on the look your going for and what looks good to you.
> I would have used Shellac on the knots to stop the bleeding.


Exactly. I assume you want it to look like painted wood, not painted vinyl. Wood has knots and imperfections, that's why we like it. I woodent (LOL) do too much filling unless it needs to be sealed for some reason. (bugs, insulation, meeces, etc.) You definitely should seal the knots with a shellac or shellac based primer. It is the only thing that will keep any sap bleed in check for any length of time. (BIN primer). And don't be shy about how much you put on. They need a good solid coat on them.


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## benjamincall (Apr 25, 2008)

joecaption said:


> All depends on the look your going for and what looks good to you.
> I would have used Shellac on the knots to stop the bleeding.


I don't recall having seen anything other than clear grades painted in a semi-gloss white before, so I'm not sure.



klaatu said:


> Exactly. I assume you want it to look like painted wood, not painted vinyl. Wood has knots and imperfections, that's why we like it. I woodent (LOL) do too much filling unless it needs to be sealed for some reason. (bugs, insulation, meeces, etc.) You definitely should seal the knots with a shellac or shellac based primer. It is the only thing that will keep any sap bleed in check for any length of time. (BIN primer). And don't be shy about how much you put on. They need a good solid coat on them.


I'm of the same opinion about the wood, but I wasn't sure if the glossy finish on knotty wood is taboo. I liked the idea, but I wasn't sure if it would look good in practice.

The planks are going over drywall, and I have no holes that extend all the way through the wood. The paint store own reccommended not using the primer other than on the knots because to avoid topcoat issues. Hence, my question about how far to go beyond the knots.


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## klaatu (Mar 9, 2015)

benjamincall said:


> I don't recall having seen anything other than clear grades painted in a semi-gloss white before, so I'm not sure.
> 
> 
> 
> ...


Well the part of the wood beyond the knots is probably going to be pretty absorbent, which could cause problems with the "hold-out" or ability to keep an even sheen. This one of the reasons this type of wood, when used indoors in particular, is typically painted flat. Along with the ability of flat to hide surface imperfections, which again kind of defeats the purpose of the knotty pine. I would recommend in my store that a high solids primer of some sort should be used over the whole thing.


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## ToolSeeker (Sep 19, 2012)

B-I-N is a shellac primer. I think I would use the BIN on and around the knots then maybe a sealer like Guardz on the rest. But lets see what the others say.


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## klaatu (Mar 9, 2015)

ToolSeeker said:


> B-I-N is a shellac primer. I think I would use the BIN on and around the knots then maybe a sealer like Guardz on the rest. But lets see what the others say.


That would be a good recommendation, as the Gardz would seal the wood against holdout issues, but wouldn't fill the texture of the wood. That would allow the natural texture of the wood show through. Good call.


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## ront02769 (Nov 28, 2008)

Of interest (to me at least) is that there are now multiple types of b-i-n. The original is a true shellac-based (I.e. Insect resin mixed with alcohol) product with some white colorant added. Hard to use, fast drying, killed your brushes, and cleaned up only with alcohol. The BIN Advanced product is synthetic shellac and is a water based deal, claims to do what the original bin does. Ron


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## Nestor_Kelebay (Jun 17, 2008)

Whenever anything bleeds through a primer or a paint, the reason is that something in the substrate is dissolving in the wet film of the primer or paint and diffusing through the wet film to the surface where it leaves a discolouration on the primer or paint.

In the case of pine, there are tannins in the wood that dissolve in water and will bleed through latex primers and paints. The tannins are most concentrated in the knots, and so that's where you need a stain blocking primer like BIN the most. Since tannins aren't soluble in alcohol, the tannins won't dissolve in the wet BIN primer, and hence won't "bleed through" BIN. Once the BIN dries it forms a physical barrier between the tannins in the knots and any water based primer or paint you apply over the BIN.

If it were me, I would use the BIN on the knots where it's needed most, then go over the whole thing with an alkyd primer. The tannins won't dissolve in the mineral spirits thinner of an alkyd primer. Then, top coat with the latex paint of your choice.


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## chrisn (Dec 23, 2007)

Not sure I would use Gardz on bare wood, although it sounds like a good idea, it is NOT in their recommendations

* Recommended Uses​*​​​​– Apply to interior walls, ceilings and​
related surfaces. GARDZ is recommended for sealing probleml​ porous surfaces such as bare and damaged drywall, plaster,​ cement and cementitious coatings, spackling paste and joint​ compound, calcimine, stucco, acoustic and texture finishes,​ uncoated wallpaper, etc. GARDZ will also adhere to and seal in​ old wallpaper paste and adhesive residue. GARDZ has a milkyblue​ color that helps to determine where it has been applied but​ dries water clear. It is formulated for use directly from the​ container; tinting is not recommended.


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## ToolSeeker (Sep 19, 2012)

Thanks guys I wasn't sure. To the OP cover stain it is or any oil based primer.


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## Nestor_Kelebay (Jun 17, 2008)

PS: In case anyone is interested...

In Chrisn's reference on Gardz sealer, it says:

"GARDZ has a milkyblue color that helps to determine where it has been applied but dries water clear."

How is it possible for something that's milky blue and opaque in the can to dry to a solid that's both transparent and colourless?

It's two things that both happen at the same time as the Gardz dries:

1. How does the blue colour disappear?
The Gardz contains something called a "leuco dye". A leuco dye is a molecule that can change it's structure depending on it's environment, and in so doing, absorb certain frequencies of light, thereby giving it colour by the frequencies of light that are reflected and not absorbed.

The leuco dye in Gardz will be blue as long as the dye molecules are immersed in water. As the water evaporates from the Gardz film, the leuco dyes change their structure to one that doesn't absorb any frequencies of light, and thereby becomes colourless.

http://en.wikipedia.org/wiki/Leuco_dye

The problem with leuco dyed primers is that the blue or pink colour can return if the wall or ceiling gets wet again. But, once the wall or ceiling stays dry for a long time, the leuco dye tends to keep it's structure and remain colourless.


2. How does it go from opaque to crystal clear?
Latex primers and paints consist of gazillions of tiny spherical blobs of plastic called "resins" suspended in a solution of water and a water soluble solvent called a "coalescing agent".

(Probably the most commonly used coalescing agent is a chemical called "Texanol" made by the Eastman Chemical Company. You can give your house a "freshly painted" smell by just misting some Texanol into the air of each room. Google Texanol and learn all about it.)

When you spread the primer or paint on the wall, the first thing that happens is that the water evaporates. As that happens, the spherical blobs of plastic find themselves surrounded by the coalescing agent at an ever increasing concentration. The coalescing solvent gets absorbed into the plastic blobs making them very soft and sticky. The same forces of surface tension and capillary pressure that cause tiny droplets of water to coalesce into large rain drops in clouds then take over and cause each soft sticky resin to stick to and pull on each of it's neighbors. As that "coalescence" or "film formation" occurs, all those plastic resins coalesce to form a continuous film of soft sticky plastic over the substrate, typically with coloured pigments suspended inside the film very much like raisins in raisin bread. Over the next several days, the coalecing solvent evaporates, filling the room with that "freshly painted" smell, and the plastic film hardens up and loses it's stickiness.

It was these plastic/water interfaces that reflected and refracted incident light to give the latex primer or paint both opacity and a white discolouration in the first place. That is, the latex primer or latex paint was
opaque in the can because the plastic resins reflected and refracted light just like the water droplets in clouds make clouds opaque. Also, the latex primer or paint was "whiter" in the can than the dried paint on the wall for the same reason that clouds and snow banks or the head on a beer are all white in colour even though nothing inside any of these things is actually white in colour. It's the reflected and refracted light of all frequencies coming from everywhere in the wet primer or paint that your eye sees as the colour "white". As the plastic/water interfaces disappear when the latex primer or paint forms a film, the paint or primer darkens somewhat as that artificial white discolouration disappears. That is, latex paints darken as they dry for exactly the same reason that snow loses it's white colour as it melts to form water. Similarily, latex paints and primers lose some of their opacity or hiding ability as they dry for the same reason that snow is opaque but water is transparent. The ice/air interfaces that reflected and refracted light to give the snow it's white colour and opacity disappear resulting in both the white colour and the opacity disappearing, leaving a transparent film.

(Real primers and paints don't dry transparent because they have other pigments in them that make them both white and opaque, but that's another matter. What we're explaining here is why latex primers and paints darken and lose some of their hide as they dry to form a solid film.)


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## Nestor_Kelebay (Jun 17, 2008)

PS2: For anyone that's even more interested...

You can use the behaviour of light to understand how wet T-shirt contests work, too...

The reason why wet cotton is more transparent than dry cotton is because the refractive index of cellulose (which is what cotton is) is 1.55

This is closer to the refractive index of water (1.33) than it is to the refractive index of air (1.00).

Consequently, light traveling from water into cellulose reflects and refracts less than light traveling from air into cellulose.

That means light travels a straightER path when it travels through wet cotton than dry cotton. Or, light behaves in wet cotton more like it would if the wet cotton were not even there.


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## chrisn (Dec 23, 2007)

Nestor_Kelebay said:


> PS2: For anyone that's even more interested...
> 
> You can use the behaviour of light to understand how wet T-shirt contests work, too...
> 
> ...


What? no pics to demonstrate this phenomenon?:wink:
Also the Gardz right out of the can is not all that milky blue and is very hard to see when applying, no matter what they say:laughing:


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## klaatu (Mar 9, 2015)

Nestor_Kelebay said:


> PS2: For anyone that's even more interested...
> 
> You can use the behaviour of light to understand how wet T-shirt contests work, too...
> 
> ...


You Chemists are a real hoot! lol. Honestly there is great information there, but maybe a little more than most people can digest. But I myself love getting this kind of info from people more informed then me, that's why I have kept in contact with some of my old paint chemist friends from days gone by.

But in honestly, I spend most of my selling time trying to convince people why they shouldn't buy the $4.97 can from Menard's. So I won't even try to pass this on to them. Lol.

But, back to the op, there are lots of options for a primer, and using an alkyd over the areas that are not knot's,(lol) is definitely the BEST way to go. But also keep in mind that this knotty pine is more than likely kiln dried (might want to check), and it is an interior application, so assuming it is not being put in a basement or a bathroom or exposed to excessive moisture, a water based primer or even sealer should suffice. But you also have to take into consideration the idea of back priming that knotty pine to help keep tannin bleed at bay. It depends on how far you want to go in reality. If you go the full bore exterior best practices, you would spot prime all the knots with BIN, front and back and even sides where the knots come to the edge. Then prime all six sides of each piece with an exterior alkyd primer,(not a multi purpose primer!), then topcoat with two coats of a premium acrylic paint.

Then you still may have a long term issue with pine sap coming from the knots. And you will have knotty pine that faintly resembles knotty pine. It kind of also depends on what your expectations of as far as what you want it to look like in the end.

I have seen people use gardz on wood for years, although I don't really know how it held up as I just sold it. I think the big issue actually is that Zinsser has other, more expensive sealers they want to sell for wood. And I doubt that Gardz would sand very well on wood.


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