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Discussion Starter · #1 ·
I don't think it matters either way, but which do you prefer for sealing knots in exterior wood and why?

What situation would you use one or the other and why?

I am asking in relation to siding that is going to be coated with an acrylic stain. The previous painters (CollagePro, go figure :whistling2: ) didn't honor the knots and there is some discoloration that I will need to take care of, obviously, before I apply the topcoat.

Normally I would just use B-I-N. All I want is to use the best available product.
 

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Rock On
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B-I-N is a white pigmented shellac

It's the only one I use for sealing knots
I've not tried the SWP product

I've not used non-pigmented shellac for that purpose
 

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Discussion Starter · #9 ·
I would use white pigmented if it were a lighter color and clear if it was a darker color now and you were going to recoat witha dark color.
Steve
Why?

Stain.. soild body? I'd use clear in that case. I normally only use clear for sealing plaster before a repair.
And, Why?

Thank you! :)
 

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The Lurker
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if your doing two coats flashing usually is not a problem. A lot of my exteriors the last few yrs are re paints that I did 6-8 yrs ago. So color change there is not so one coat of provt and its good to go. (after cleaning of coarse)
 

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Thats what I use, I am not sure if its for interior only but I have had good success with it outside. I was told that tip from a old paint contractor that used the mom and pop store I used to use where my old house was before I moved two years ago.
 

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Shellac has been used for hundreds of years for sealing knots. But in the old books it says to mix it. Most zinnser is 3 lb cut. If you want your clear to really seal, when the can has set for a while, take out a cup or two of fluid off the top, (alcohol) this gives you more concentrated shellac, less solvent. Not sure about BIN as I think there is less alcohol but more pigment than shellac.
 

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I don't think it matters either way, but which do you prefer for sealing knots in exterior wood and why?

What situation would you use one or the other and why?

I am asking in relation to siding that is going to be coated with an acrylic stain. The previous painters (CollagePro, go figure :whistling2: ) didn't honor the knots and there is some discoloration that I will need to take care of, obviously, before I apply the topcoat.

Normally I would just use B-I-N. All I want is to use the best available product.
I would not recommend any type of shellac for exterior priming, as it does not hold up to moisture. I have been there and done that, trust me it is not good for exterior work.
 

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HA, ( funny,looking at that the HA wasn't suposed to be a laugh... It was just short for your name)

You are a Humble guy because I know (from what I've read of yours) that you know that there one-in-the-same. The thing that many painters don't think of, is that shellac doesn't hold up for long in the elements at all. The reason I know they don'r realize this is because of all the houses I've seen that are spotted. That means that they are dealing with the knots as a separate step, rather then along with the finishing step. Shellac whether clear or pigmented will start to break down when exposed to the sun within hours. The reason you see the knots peeling within a year or so, isn't because the knot is a harder wood or it's leaching tannins, it's because the shellac has lost it's bond.
Get your self one of those plastic coffee containers with a lid. Punch two holes in the can at the top of each side. Run a piece of string through to form a loop. Cut a slit in the lid, and slip in a 2" throw-a-way bruch through the slit, this keeps the shellac from drying out. Bring it up the latter with you and hang it with a hook. Kill the knots first and start painting. The shellac sets up in minuets, so that by time you get to them their'll be dry to paint/stain over. I've never had a problem.

Pete


I don't think it matters either way, but which do you prefer for sealing knots in exterior wood and why?

What situation would you use one or the other and why?

I am asking in relation to siding that is going to be coated with an acrylic stain. The previous painters (CollagePro, go figure :whistling2: ) didn't honor the knots and there is some discoloration that I will need to take care of, obviously, before I apply the topcoat.

Normally I would just use B-I-N. All I want is to use the best available product.
 

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Don't mind the spelling. It's late and I typed it fast. Kidn-a hard to believe that I've been painting for 30 years and I spelled ladder with two t's. What can I say !!

re-Pete

HA, ( funny,looking at that the HA wasn't suposed to be a laugh... It was just short for your name)

You are a Humble guy because I know (from what I've read of yours) that you know that there one-in-the-same. The thing that many painters don't think of, is that shellac doesn't hold up for long in the elements at all. The reason I know they don'r realize this is because of all the houses I've seen that are spotted. That means that they are dealing with the knots as a separate step, rather then along with the finishing step. Shellac whether clear or pigmented will start to break down when exposed to the sun within hours. The reason you see the knots peeling within a year or so, isn't because the knot is a harder wood or it's leaching tannins, it's because the shellac has lost it's bond.
Get your self one of those plastic coffee containers with a lid. Punch two holes in the can at the top of each side. Run a piece of string through to form a loop. Cut a slit in the lid, and slip in a 2" throw-a-way bruch through the slit, this keeps the shellac from drying out. Bring it up the latter with you and hang it with a hook. Kill the knots first and start painting. The shellac sets up in minuets, so that by time you get to them their'll be dry to paint/stain over. I've never had a problem.

Pete
 
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