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Discussion Starter · #1 ·

Hope you folks will help me out on this one:

I have run into an interesting situation I need your help with. I am going to spray paint two very large barns. The larger of these two barns has been completely restored. The client used knotty pine wainscot and soft, rough sawn pine with knots as replacements for the original barn boards.

I suggested we use an oil base, solid stain (client wants white). Two coats of sprayed stain, in my mind would have provided excellent long term wear. Although the knots would bleed through without the use of special primers, this approach seemed reasonable and affordable.

The client has had several weeks to live with a test area I did. He is not sure at all he wants to live with the knots. The barns are being sprayed, spot priming is out. So, the questions are:

Is there a primer that can be airless sprayed with no back brushing involved that will prevent bleed through? The larger barn is 40x60x60’ high. Can I spray a shellac based primer without killing the internal parts of my airless? Do you suggest a pigmented shellac or are there other products that will meet the specs I indicated? The barns can be brushed and rolled, but obviously at much greater expense. Can your make some recommendations for which products would be candadates for this type of work? Your responses are greatly appreciated.

JTP
 

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Is there a primer that can be airless sprayed with no back brushing involved that will prevent bleed through?


No. On exterior wood, especially new wood you MUST back brush or back roll.

The larger barn is 40x60x60’ high. Can I spray a shellac based primer without killing the internal parts of my airless?


No. Shellac based primers are not recommended for exterior "all over" priming because when they dry they become very brittle and crack. This would totally negate the reason for using a solid stain in the first place. The only reason to use an exterior solid stain as opposed to a paint is because it resists cracking, peeling, and checking.


Do you suggest a pigmented shellac or are there other products that will meet the specs I indicated?


No. See above.

The barns can be brushed and rolled, but obviously at much greater expense. Can your make some recommendations for which products would be candadates for this type of work?
The best approach would be to spot prime the knots with Zinsser's clear Shellac and then 100% prime with a high quality oil based primer (Zinsser's Cover Stain) and two coats of an Acrylic or Oil based solid body stain.

I don't think any manufacturer or sales rep would recommend applying two coats of oil stain, by spray, on new wood, with no primer...



If he doesn't want to pay for a quality job, he is going to have to 'live with' a sub standard one...
 

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I have sprayed many buildings that were done with rough sawen pine and I can tell you that IMHO there is not one product out there that is sold to seal off knots that works. The only thing that I have found to work is sealing them off with brown exterior carpenters glue. This is a slow job to do but not really any worse then spot priming them with one of those products that does not work.We always back brush any area that we shoot with the airless.I have never have the glue let a knot burn through. Oh ya this method was told to me by a paint chemest from a very large paint company that manufactures the very products that are sold for knot sealing. Go figure :blink:
 

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Discussion Starter · #5 ·
JTP Says Thanks

Thanks much for the excellent and informative responses to my questions. The carpenter's brown glue is totally new to me for sure. From the look of these two responses, my customer is going to have to settle for a substandard job or pay more for the spot priming, finish priming, and top coat(s). I have passed this information along to my customer and will be meeting with him shortly. I plan to use a bucket truck with a 66 foot reach for the larger barn. It costs 4 grand a month to rent. The client is paying for the rental. It will be interesting to see how this turns out. I'll let you know if you're interested.

And once again--Thanks much for this information.

JTP
 

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This just in

I was just told about >this< by one of our sales reps. It looks pretty cool. I have a big rough sawn cedar job coming up with a ton of existing bleed through. I plan to use it on that job to see how well it works.
 

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Tannin bleed is one thing, not that hard to hide.Cabots Problem Solving Oil primer will do that easily. Knots on the other hand are a different kettle of fish. The wood surronding the knot will expand at a different rate than the knot,allowing the sap to bleed out. The glue seems to have enough flexability to expand and contract at the same(more or less) rate as the wood and knots.JMHO ;)
 

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Forgot to add... A job like that I would never prime. I would use Cabots Provt latex stain. No primer required. Shoot with a 212 or 412 tip and back bush. add 10 oz of flotrol to each gallon of stain. Seal all knots with glue. Your good to go.

Stan
 

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Discussion Starter · #9 ·
I appreciate the responses and suggestions Painterman and Humble Abode. The latex stain idea is similar to my original suggestion with the difference being my idea was to use Cabot's Oil Stain. What is the advantage Stan in your experience? Also, is there a specific brand of carpenter's glue you use and reccomend? Thanks much.

JTP
 

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I appreciate the responses and suggestions Painterman and Humble Abode. The latex stain idea is similar to my original suggestion with the difference being my idea was to use Cabot's Oil Stain. What is the advantage Stan in your experience? Also, is there a specific brand of carpenter's glue you use and reccomend? Thanks much.

JTP
I really do not like using any type of oil products. I don't see the need to any more. The 100% acrylic latex stains are really good. Great colour retention.In my part of the world we get very hot summers wet falls and cold winters and I have had no problems with provt. Provt is a very heavy body stain that you can make cover in one coat but I would always 2 coat it just to make sure.As far as the glue I did experiment with several types. Use the best exterior BROWN glue that you can get. Most of them say paintable on the bottle.Tite Bond 3 works very well.
 

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Discussion Starter · #11 ·
Painterman--Can you share with me how you put the glue on as in:

Do you cut the glue at all?
What type of brush and or roller is used?
How do you prevent the glue from setting up as you work--wet edge time?
How much material do you put in your cut bucket?

Any and all other information relevant to using your knot killing system is appreciated.

JTP
 

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Painterman--Can you share with me how you put the glue on as in:

Do you cut the glue at all?
What type of brush and or roller is used?
How do you prevent the glue from setting up as you work--wet edge time?
How much material do you put in your cut bucket?

Any and all other information relevant to using your knot killing system is appreciated.

JTP
Do not cut the glue.Remember brown exterior glue only.
We brush on with any cheap throw away 1 inch brush
I want the glue to set up. Just brush on the knot or sap pocket and let dry. In warm weather it will dry in about 10 min.
Some of the glue bottles have large tops that come off. Just dip in your brush and paint on. Just like spot priming.
If you have any more questions let me know.

Stan

www.victorianworks.com
 

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Forgot to add... A job like that I would never prime. I would use Cabots Provt latex stain. No primer required. Shoot with a 212 or 412 tip and back bush. add 10 oz of flotrol to each gallon of stain. Seal all knots with glue. Your good to go.

Stan

Couldnt agree with you more!
 

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If it's not to late,Ive never had this problem that I can recall but I do know of an old school trick they may work.sanding sealer works just like zinnser or kilz on sheet rock.I know it sprays good I use it all the time for office doors.maybe it'll work.
 

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If you're going to be up there putting glue on the knots, why not spot prime the knots with the shellac like mentioned. The only diff is that you will probably have to hit them twice. I use spray cans of shellac, it's much faster.

...and this must be a really nice barn for the guy to care about knots on the ceiling. If he is actually paying you to make this ceiling look like a million bucks (which will cost a heck of a lot if you're bidding correctly)...here's to you :notworthy:
 

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Discussion Starter · #16 ·
Rich--

No ceiling work. Two exterior barns, wainscot knotty pine t&g on bottom floor--exterior--raw, rough sawn pine board 2nd and third stories. Obvioulsy the wainscot has more knots than the rougher pine boards, but one heck of a load of knots all the way round.

I've got differing opinions on just how to prime the knots to avoid bleed through. The glue idea is very interesting, but I am tending toward a spot prime with pigmented white shellac and finish with Cabot's ProVT Latex. Going to have to use one hugh load of spray cans. Will probably just use the old fiver and a zip roller.

I put the job off till next year. I wanted the lumber to dry out more. I am investing in a moisture meter as well since I really would like to take readings of wood--especially decks after pressure washing--both the barn job as well.

Thanks for the ideas. Your feed back is appreciated.

JTP
 

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Discussion Starter · #17 ·
If it's not to late,Ive never had this problem that I can recall but I do know of an old school trick they may work.sanding sealer works just like zinnser or kilz on sheet rock.I know it sprays good I use it all the time for office doors.maybe it'll work.
Next Level-- Another great suggestion. I can try the sanding sealer too. I have used several different materials to kill hot spots on plaster and or sheet rock (dry wall out West). Sometimes any old white latex paint stops the flashing. Mostly a good oil primer if two top coats are applied--and I have used shellac to stop paint peel after skimming. Not too late for suggestions b/c I put the job off till next year. Thanks a lot for your ideas.

JTP
 

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Spray shellac...you must be kidding. If you were ever to stand even a chance of shellac working ,it would have to be a 5 lb cut. A 5 lb cut would never ever spray out of a rattle can. Oh ya latex paint it does not like to bond to shellac.Shellac dries very hard,latex paint has some flexablity,can you see what is going to happen.:no: Seeing that you have some time before you start the job,seal off several knots with all the different sealers you have and coat them with some provt.leave them in the sun for a day or two and I can bet you I know the out come. The knots that were sealed with glue will not burn through and all the others will. I would be very careful adding anything to the stain that can make it go so hard after a day that you can not use it. I wonder what Cabots would say about that in their product.
 

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Discussion Starter · #20 ·
Replies to Humble and Painterman

The give and take on this thread is truly enlightening. Just goes to show you there's more ways to skin a cat than we all thought. I can tell you that I can in no way afford to mess this job up.

I am considering all of the suggestions that have been put forward and weighing the merits of each suggestion. I like the fact that folks are making reccomendations.

Since I do have the time, I believe I will try painterman's Tite Bond III brown carpenter's glue sealing system and do some testing. I will also use bins on a test section and two coats of top coat Cabot's ProVt over whatever primer I am using over the knots.

By next late Spring-- I'm gonna know the deal. The fact that shellac is so brittle and latex is meant for expansion and contraction leads me to tentatively agree with painterman. Using a brittle primer like bins or another pigmented type shellac and top coating with a latex product seems self defeating.

Please accept my thanks for the input. Humble. I looked at XIM when you orginally posted it and again tonight when I read the new responses. If I decide this product could work well, I'll do a test prime and top coat with it as well.

JTP
 
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