“Why External Finishes Fail” (FHB #110) recommends these preventive measures:
1. Seal the wood with a paintable water-repellent preservative.
2. Use a good-quality oil-based, alkyd-based or stain-blocking acrylic latex-based primer; the label should clearly state that the primer can block the bleeding of extractives.
Special primers are available for knots.
3. Apply two coats of a good-quality, all-acrylic latex house paint over the primer.-
Home Depot has a bewildering array but nothing specifically said “Paintable, water-repellent preservative” or “knot primer”. Could you please suggest some specific brand- and product-names? Thank you!
Janet
P.S. Last time I used Kilz Premium for primer and Ace Hardware’s house brand for the top coats, but the knots still bled through.
Replies
Janet,
The best stain blocking sealer is shellac. Seals knots, tannins, and various other stain sources better than other primers or primer/sealers.
When you're painting, you can use a pigmented shellac as a primer/sealer. Zinsser "Bin" is one brand/product that comes to mind.
Paul
Furniture Finish Wizard
Zinzer shellac is good stuff. If you're worried about show through, put a couple three coats over the knots/stains. Shellac dries in less than five minutes.
As to paints, I prefer Pittsburgh myself, but that's in part because the local dealer is willing to order stuff like raw linseed oil and raw tung oil when I need it. He gets a giggle out of the fact that I make my own finishes.
I've used Sherwin Williams (which was my dad's preferred brand) with no complaints at all. The place I work for uses Duron. They like it.
Leon Jester, Roanoke VA
Using shellac outdoors is really a no-no. Shellac has a low melting point, the sun hitting the paint and its thermal gain is enough to soften and loosen the shellac, thereby disturbing the primer and paint layers above it. It will eventually flake and lossen. Some exposures like a north or east area wont be as prone to this activity but are still subject.
Sealing knots or sap on exterior should be done with an oil based product. Water based products still allow a tannin bleed through due to the tannin being leached out by water in the paint It reactivates the stains. The stain blocking rule applies. Water based problems such as tannin, sap, or stains caused by the results of water need an oil based solution. Stains caused by greases, oils etc should be dealt with by water based stain solutions. Using the wrong stain based solution will reactivate the stain causing painting problems.
If you really want paint help when you go to the store, dont go to the big boxes like lowes or home depot. They cant offer you painting solutions with much advice. Head to your local pro paint store that sell brands like Sherwin Williams and Benjamin Moore, or Pittsburgh paints, devoe. They will take the time to advise you on proper choices where at the big boxes they just point you to the labels.
Where are you getting your information about shellac? How does what you are advocating square with the various Zinsser exterior products that are shellac based?
Shellac is not heat tolerant, thats a fact. The only zinser products that are shellac based are the clear/amber 3lb cut shellacs and the BIN shellac primer. While the advocate spot priming only in exterior use, that area where the shellac has been applied can soften when heated. Causing paint failure. An easy similarity is vinyl siding, Vinyl absorbs heat, white less then say tan. Without accounting for expansion and contraction of the heat, vinyl will warp like fresh milled board in the hot summer sun. Paint will attract heat on a house, areas that has been spot primed with shellac will begin to soften (or warp like vinyl)
Shellac is also not water resitant, thats a fact. Latex paint will allow water through, thats a fact. Over time water will attack shellac and weaken the spot priming. Causing primer failure resulting in paint failure. Water infiltration can happen from exterior rain and dew to interior vapor being released.
Painting with Extremly light colors such as whites and off whites the thermal effect isnt as noticeable. Exposures on the North and East as well. However adding any tint past a certain point will begin compounding its thermal gain. Thats why you NEVER paint a dark color on a door with a glass or plexiglas storm door with exposures to the sun, It will cook your paint.
While they may advocate using shellac primers outdoors, its by no means its worth using though it can be used. The shellac is the binding agent, a very good binder, it can bond to most surfaces, but in the zinser products, its the only binder. That binder will soften and its ability to bond reduced with water and heat.
Test the shellac yourself, prime with kilz on one half, BIN on the other, to speed up the test paint it black, expose it to the sun. Study the paint.
The FHB recommendations come straight from the Forest Products Lab (in Madison, WI) research that I first heard about nearly 25 years ago. So, it is ####time tested recipe for getting a high quality, long lasting paint job on exterior surfaces.
Since first learning about this procedure, I have been using the Benjamin Moore products noted below. Other manufacturers make similar products, and I am not saying the BM stuff is the best available -- but I can testify that they have worked for me over the long term:
1) Moorwhite Primer -- alkyd based.
2) MoorGlo -- an acrylic latex with a very soft sheen.
I stopped using the wood preservative after a few years, and for weathered surfaces will instead use two coats of the above primer -- the first thinned out about 50% (for better penetration).
I really hate exterior painting, and I therefore have a bias against HD products for this purpose. I think (perhaps wrongly) they are more interested in price points, and I would rather spend the extra $$ for exterior paints that have a high probability for lasting as long as possible.
As an option, you could visit a Sherwin Williams store that caters to painting professionals, where I think you are more likely to find expert help. Some of the mall type stores are staffed by people who know next to nothing. Any SW expert will be able to tell you exactly what they have which competes directly with the BM products mentioned above, both of which are well known in the trade.
Nikki,
I didn't understand the second sentence of your posting. Are you saying that the information is outdated? That would explain why I never hear of anybody bothering to apply a "paintable, water-repellent preservative."
Janet
Do you mean the sentence about clear wood preservatives?
25 years ago, when I first discovered this "system," I used a common preservative (Penta something or other). Soon after, it was declared toxic, and taken off the market (at least for individual consumers).
There are a wide variety of clear wood preservatives on the market now, if you want to try one. But I would be careful, since some have a waxy substance in them that may not work well under paint.
You might try finding the web site for the Forest Products Lab and see what they have to say about the oils. They probably won't talk brands, but they may well give you enough guidance to select the right stuff in a paint store.
Howie suggested checking out Consumer Reports, which is good advice. However, I have never found their paint recommendations to be especially helpful, since they will recommend one manufacturer for one paint color, and another for a different color.
EDIT: HERE IS THE LINK FOR THE FPL INFO ON PAINT AND FINISHING:
http://www.fpl.fs.fed.us/finishing.htm
Edited 9/6/2004 12:26 pm ET by nikkiwood
>>I have never found their paint recommendations to be especially helpful, since they will recommend one manufacturer for one paint color, and another for a different color.
I wouldn't consider that a problem if you want the "best". Consumer Reports reports the test results and puts them in order. If you want to get only one brand, you can still optimize your selection so that your get the brand that does the best in all colors. In some cases, the differences may be very small.Howie.........
Nikkiwood, I searched everywhere for Benj. Moore's "Penetrating Alkyd Primer 100." Finally found a store with three slightly rusty cans of it. The clerk said [he thinks] they can't order it anymore because of new, stricter VOC regulations here in California.
I had the same problem trying to buy Wolman's "Woodlife Classic II".
Just when you find something that everybody recommends, it becomes outlawed!
Took your advice and bought a 3", angle-cut Purdy with white bristles. Some women buy new clothes when they want to treat themselves. I wear knockabout clothes and buy a new tool instead. :)
Janet
The BM primer I mentioned was called "Moorwhite Alkyd Primer." I suppose for marketing reasons, BM keeps diddling with product names; a couple of years ago they started called all (or most, anyway) of their primers "First Coat" -- with the old name appended, kind of like a subtitle.
Because of CA's more stringent VOC regs, it is entirely possible this product is no longer available out there.
Most paint stores that sell BM have some old guy that has been in the business for 20-30 years. Find that guy, and he will be able to tell you if Moorwhite is still avaialble in CA, and if not, what has replaced it.
I know what you mean about tools -- I think I have more paint brushes than Imelda Marcos had shoes.
If you are looking for brand names, go to your library and look at the past couple of years of Consumer Reports. They have be running a continuous long term test of exterior house paint and reporting on the results in the June issue.
Those results name the names of those products that are doing best and those that are failing.
I haven't read CR myself but a couple of our painting customers have told me that it lists "Behr" (Home Depot brand here) as the "best" exterior paint. In two words; it ain't ! Even the second and third lines from other companies are better than "Behr". It makes me wonder what the heck they compared it to!
I would trust the recommendation of a commercial paint store employee (Sherwin Williams, Kelly Moore, Benjamin Moore, etc.) over Consumer Report any day of the week.
My 2cw.
Regards,
Mack
"WISH IN ONE HAND, #### IN THE OTHER AND SEE WHICH FILLS UP FIRST"
Mack,
I am one of those who always consults CR before buying any appliance, car, etc -- but I agree with you when it comes to their paint recommendations. I know their testing is as scientific and systematic as they can make it, but their paint choices (over the years) have struck me as odd.
What you say about the Behr exterior paints is interesting. I have never tried any, but I did have occasion to use one of their interior latex paints (Premium Plus) for a client awhile back. I have used Ben Moore paints pretty much exclusively for 20-30 years, and this stuff from Behr was markedly superior -- in terms of coverage and ease of application. And, it was almost $10/gallon cheaper than the BM paint.
nikkiwood,
This is getting a bit off the subject but C.R. (I'm told) also ranked the Chevy Astro as bottom of the heap in mini-vans for a number of years. There are thousands of them still around from the late eighties and early ninties and a majority are used by contractors. We have two, one with 235k miles and one with 290k and I wouldn't hesitate to get in either one for a cross country trip (I'd actually take the older one, it has a better stereo). The Chryslers that were so highly thought of when they first appeared are now found dead all over the place or for sale for next to nothing.
I take everything I hear from CR with a grain of salt.
Regarding Behr paint, I can't speak about the interior stuff as I can't recall any projects we used it on. The exterior stuff that we used last year on two jobs was inferior to both SW A-100 and Kelly Moore 1240/1245. I'm not a painter but administer a paint contracting business. The couple of times we had to use Behr, I thought I'd never hear the end of the complaints from the painters about coverage, sprayability etc, etc. Besides that, it costs us more. Our volume at the paint stores puts us at a discount level that makes buying elsewhere just plain dumb.
Many times people will call for an estimate and ask "what if we buy the paint" like they think we make a killing on the material. I explain to them that if they want to spend more money that's their option but that we can buy paint WAY cheaper than they can and if they buy crappy paint, we won't use it.
I wouldn't put Behr in the "crap" category but it is not cost effective for us and I don't think it compares to Sherwin Williams, Kelly Moore, BM or even Parker for that matter.
BTW, if you like BM products but don't care for the "gold plated labels" try their "Super Spec" line. It's designed for contractors and pricing is very competitive.
Regards,
Mack"WISH IN ONE HAND, #### IN THE OTHER AND SEE WHICH FILLS UP FIRST"
I brought up the Behr example as a way of suggesting it is not always reliable to settle on one manufacturer, then buy only from that line. In this case, the exterior Behr products are apparently wanting, but I can testify that the interior paint I tried (Premium Plus) was superior to BM, and $10 less expensive (than the BM discount they give me).
As far as Consumer Reports is concerned, their buying guidelines have been astonishingly reliable for me over the years.
With cars, I think their judgments are heavily weighted by safety factors (and their views are sometimes idiosyncratic), and reliability data (generated by reader surveys, which probably don't have the scientific foundation they could have). But even so, it is the best effort I know about to provide unbiased, objective information to consumers.
In recent years, CU has primarily rated M.A. Bruder (SeaShore Flat) and Califoria (Fresh Coat Velvet) as the two best exterior. However, both are only available in the NorthEast. Glidden (Endurance Satin & Semi-gloss), Glidden (Spread Dura Satin & Semi-Gloss) and a couple of other Glidden paints took rankings 5 - 10 followed by Sears (Best Weatherbeater) in 11-12. No Behr did well in exterior paint tests nor did Benj. Moore.
They go on to recommend buying the top grade from each manufacturer as these lasted much longer than lower grades.
For interior paints, Behr, Ben Moore, Valspar are listed 1-3 but looking at the article is important because certain types of paints within the brand were much better than others.
I think the problem with many using Consumer Reports is that they only focus on the ratings. There is much relevent info in the article that may cause a reader to make a choice that is not the "top" performer. So when someone says that an item is "best" without the accompaning data, the info is not too useful.Howie.........
I stopped using CR as a gold standard when they reported on Coffee, saying that "all their Starbucks beans were burnt." Ah, the Starbucks full city roast (no CR, it isn't burnt, that's how it's supposed to be.)
You know, they say coffee is addictive but I've been drinking a pot of Starbucks every day since 1981 and is hasn't affected me at all....
Just to keep with the thread, I would never use Shellac or a shellac based product on an exterior job.
Paul
The whole CR and paint tests cant really truely give the best results. I mean i know SW and BM have so many paint lines its not funny. I know in SW paints they have the retail line and the professional line. Dont even know if the test could give a result on the spatter and how it holds a wet edge.
Though i think they did rate BM satin impervo as the best oil based paint, they were right on the money. That paint is the cats meow of oils that ive used, though i hear of some euro oil paints that are supposedly out of this world.
Re: Benjamin Moore paints
I started using BM paints almost 30 years ago. But 5-6 years ago, I began to perceive they were just not covering as they had in the past, mainly the latex lines, but even Satin Impervo.
I wonder if you, or any other long time users are seeing the same thing.
Clearly, all the manufacturers have been compelled to diddle with their formulas because of changing VOC regs, and in the case of BM, I am speculating they are skimping on the pigments (compared to say, 10 years ago).
Actually i think the paints have gotten better. The problem anymore im finding with coverage are the quality of the brushes and secondly the flow of the paint. The former can be fixed by hunting down good brushes. The second i believe are the VOC requirements. The old oils had more oil in them they covered and leveled better. the newer paints trying to comply with the VOC requirements leave out more of the good oils, sacrificing coverage. Penetrol Fixes this most times. As far as Latex paints, ya gotta search for em. If they could solve the open time on the new acrylics it would do wonders. Even floetrol cant keep the newer paints enough time to level off it seems.
Primers are also IMO causing some problems with paint. They just dont have enough slip to them or they have too much bite to get that first coat just right.
Ive youve noticed some old paint they are thicker dried, then they are now, that might be what youre noticing. That may be why youre perceiving a coverage problem i dont know. This thinner mil. coverage will cause some covering issues if you dont tint your primer with some colors. This in turn does cause some coverage problems if you take it at that. I guess in hindsight it seems a coverage problem, but from my perspective the paints are better, just dry a little thinner then the old lead based paint which covered well, but we all know lead paints downside.
Paints are better today, they just require a different or better prep-job then what some are used to or willing to do.
Penetrol is great stuff.
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