Nope not missing anything, I use it for spot priming knots only. Most guys will say not even for that. But I have not gone to the glue method yet
BIN for an exterior primer
I am running into guys who have been using BIN white shellac as an exterior primer. I know one set of painted new mahogany garage doors and worked behind a repair guy who was replacing exterior cedar trim boards and preprimed them with BIN. Surprisingly, the cedar primed with BIN is giving us some bleeding hassles through solid acrylic stain. I have always thought that BIN was too brittle for such wide spread exterior use (should be confined to knots only on exteriors). Not to mention it being a vapor barrier and will be unable to allow moisture from inside the house to pass. Am I missing something?
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spot prime for exteriors only
I had seen enough of it lately that I was beginning to wonder if I was the only one that felt that way. A repaint customer of mine moved into a brand new home, super high end, and the mahogany garage doors primed with BIN I am guessing will be great candidates for an early paint failure. Do not ask me why they painted mahogany garage doors, I do not even want to know. I did not do any of new construction work on the home. Even thinking about painting mahogany makes me a little sick.
Only that those guys are idiot hacks....Am I missing something?
BIN makes a great spot prime for knots, but is way too brittle for a full exterior prime
BIN-- I actually called Zinnser last year about this very topic. I am really glad I did too. Zinnser says--no way is BIN to be used as a large scale, full primer. In other words, it's for spot priming only. If you don't follow Maks comment about glue, the hagster can point you to the right link regarding how to use exterior brown carpenter's glue to kill knot bleed through.
Again--BIN is for spot priming only. It will crack from the expansion and contraction of just about any wood- a guarantee for top coat failure.
JTP
Again--BIN is for spot priming only. It will crack from the expansion and contraction of just about any wood- a guarantee for top coat failure.
JTP
Generally the pigmented shellacs regardless of make are low solids, solvent high (alcohol) coatings that provide a thin, inflexible and brittle non- breathable film. Some contain wax. Shellacs are rated by lbs. Usually 3,4, and 5 respectively, depending on "cut." Amber or Orange Shellac has better sealing characteristics than pigmented. The higher the lbs the thicker the DFT left on the surface. Usually it is used for spot priming only. Wood finishers use the ambers to seal wood, knots, butt joints and on furniture because it has a color stable hard film with virtually no permability, and seals out moisture creating dimensional stability in wood. If there is wax in the dried film, it not only compromises adhesion of the topcoat but is also too hard for the topcoat and shellac to have proper compatability. Eventually most shellac and paint/stain systems fail as wood expands and contracts due to the disparities in flexibility between films and surface. You can make your own shellac using shellac flakes and diluting in alcohol. Zinsser used to make a 7 pound amber shellac that worked great as a knot sealer. Not sure if VOC laws and raw material costs allowed it to survive.
I seal knots with aluminum paint then oil based primer then any acrylic or oil finish. It is the only long term solution I have found. Been doing it for 35 years with no failure I know of. I am talking about the big sappy knotty pine knots not every little spruce or bird eye knot. Trust me
Mo is right on, I've been using aluminum for knots for the last 30 plus years...I seal knots with aluminum paint then oil based primer then any acrylic or oil finish. It is the only long term solution I have found. Been doing it for 35 years with no failure I know of. I am talking about the big sappy knotty pine knots not every little spruce or bird eye knot. Trust me
I have made the aluminum suggestion for years. It does work great. We use to back prime all clapboards, butt joints, and windows with it.
what in the heck made you guys ever try aluminum paint???
was this a sophisticated wild azzed guess, or did this trick of the trade get handed down to you?
and backprimimng clapboards entirely with it????? what is the scoop on that??? it sounds futuristic,,,,,,,shiney aluminum paint on the backsides of clapboards
was this the beginning of reflective paints for attic spaces???
what is amazing me is that there are 3 guys here that have used this material for similar puurposes,,,,,,,
im not disagreeing,,,,,,,im curious,,,,,,
good stuff, and food for thought
was this a sophisticated wild azzed guess, or did this trick of the trade get handed down to you?
and backprimimng clapboards entirely with it????? what is the scoop on that??? it sounds futuristic,,,,,,,shiney aluminum paint on the backsides of clapboards
was this the beginning of reflective paints for attic spaces???
what is amazing me is that there are 3 guys here that have used this material for similar puurposes,,,,,,,
im not disagreeing,,,,,,,im curious,,,,,,
good stuff, and food for thought
Aluminum paints form a thin metal barrier as the solvent evaporates. Aluminum flakes form a thin monolithic film that is waterproof, creating dimensional stability in the boards. It works in a similar manner to lead based paints. The lead and aluminum stay flexible throughout the life of the coating. Since backpriming does not get UV degradation, it remains flexible and waterproof for years. Most clapboards are installed smooth side out. The aluminum paint is thick enough to fill all the peaks and valleys of the rough side clapboard. It was handed down to me by an old german carpenter that made all his own windows, doors, stairs etc. He use to order clapboards from a small mill in northern Maine. The boards all had to come from the north side of the Saco River. The clapboards had the tightest grain orientation due to slow growth. Those days are gone unless you pay $50.00 a board foot for re-claimed trees from the bottom of lakes in Canada. Just an old timer here. I know its strange!
dont use shellac outside period
I had seen enough of it lately that I was beginning to wonder if I was the only one that felt that way. A repaint customer of mine moved into a brand new home, super high end, and the mahogany garage doors primed with BIN I am guessing will be great candidates for an early paint failure. Do not ask me why they painted mahogany garage doors, I do not even want to know. I did not do any of new construction work on the home. Even thinking about painting mahogany makes me a little sick.
These high end painters must have really botched their staining job on the doors too then if they needed to paint them.
Sounds like a lot of fun :whistling2:
*edit* Just reading back I realized the above was pretty large necro-post, almost 3 years
oh well......
There are a few of them today that are primer threads.*edit* Just reading back I realized the above was pretty large necro-post, almost 3 years
Wow i've heard of this once upon a time and just forgot and never pursued it. last summer I did some ext. painting on a manison which the carpenter had built 3 humongus porches on to it.All was done with kiln dried pine.I prepped the wood by sanding spot primed with Bin two coats by the book and used Cover stain primer over all allowing sufficent drying time, then applied 2 topcoats of Duration.No more than a month or so later knots started bleeding through.I started wondering if I was doing this all for knot.Called Zinsser techs. and they told me to spot prime over the bleeding knots twice more than to reprime and topcoat.Looks great of today but it seems to me like that was awhole lot of pain and extra work which on top of it all I had to eat labor and materials.Drove me battier.Thanks I'm gonna trust your way and see what goes.:thumbup:I seal knots with aluminum paint then oil based primer then any acrylic or oil finish. It is the only long term solution I have found. Been doing it for 35 years with no failure I know of. I am talking about the big sappy knotty pine knots not every little spruce or bird eye knot. Trust me
Ahhhhhh double-necro thread! The horror!!!!!
Aluminum paint is the historical knot primer in NS.:thumbsup:Aluminum paints form a thin metal barrier as the solvent evaporates. Aluminum flakes form a thin monolithic film that is waterproof, creating dimensional stability in the boards. It works in a similar manner to lead based paints. The lead and aluminum stay flexible throughout the life of the coating. Since backpriming does not get UV degradation, it remains flexible and waterproof for years. Most clapboards are installed smooth side out. The aluminum paint is thick enough to fill all the peaks and valleys of the rough side clapboard. It was handed down to me by an old german carpenter that made all his own windows, doors, stairs etc. He use to order clapboards from a small mill in northern Maine. The boards all had to come from the north side of the Saco River. The clapboards had the tightest grain orientation due to slow growth. Those days are gone unless you pay $50.00 a board foot for re-claimed trees from the bottom of lakes in Canada. Just an old timer here. I know its strange!
Thats interesting. I've never heard of the aluminum paint trick. I always thought it was sort of a pressure thing and no coating could stop it.
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