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Old 05-31-2012, 01:11 PM   #16
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Exterior Priming Question


To all, thanks for the taking the time to respond…this is really educational.

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Originally Posted by spraygunn View Post
…This is one of the reasons you are supposed to work around the sun…
Thanks. I remember that from that last time. It was much easier to paint when you “follow-the-sun” or in our case…the shade.

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Originally Posted by Will22 View Post
...For the pictured wood (which appears to be a form of plywood siding...
Correct. When I purchased the house I thought, in my ignorance, that it was cedar. I now know that it is rough-cut pine…

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Originally Posted by Will22 View Post
...A solid stain would also be an option...
I didn’t think stain went over Latex…

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Originally Posted by Will22 View Post
...but you would have to remove all loose paint...
Which is why I asked about Zinsser Peel Stop


I want to touch on the oil comments.
My knowledge of paint (not primer) I thought:
Oil…then over with Oil = OK
Oil…then over with Latex = OK
Latex…then over with Latex = OK
Latex…then over with Oil = BAD

As understand it (please correct me) Oil dries hard; Latex soft and pliable. That’s why it’s okay to put Latex over Oil (soft on hard) versus the other way of Oil on Latex (hard on soft).

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Originally Posted by ric knows paint View Post
...This is a fascinating discussion...
Ric, Thank You for spending the time to create a lengthy and detailed response.

Fascinating education I’m getting. Thanks.

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Old 05-31-2012, 04:28 PM   #17
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To this day, I think you will find that the US Forest Product Laboratory (who isn't trying to sell anything to anybody), still recommends a long oil primer (read slow drying) and two all acrylic topcoats as the best system for unfinished wood. In the end, what alkyds still do that acrylics do not do, is penetrate the wood and thus ensure that whatever you put on top of it, will remain stuck to the wood. Yes, all the drawbacks about alkyds are true, especially as an exterior finish coat, but when it comes to priming bare wood, long oil primers are still the king. BTW, alkyds are still champs at holding out tannin bleed or any other water soluble stains better than latexes.

All this said, assuming you do all the prep right, you should still get many years of service if you choose use a premium latex primer instead.
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Old 05-31-2012, 07:00 PM   #18
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Lippy,

When I was contracting, the chemists didn’t come to me and tell me why this product was superior or not, or where the product was most effective, they asked my opinion as to how did it work, or were there any performance issues they should know about?

Most everyone here offering advise speaks from practical experience. We are all capable of reading product descriptions or MSDS sheets and derive a conclusion to a situation. However there is no substitute for experience in the field. We learn by doing and often times pay for that experience at our own expense. Assuming a product will deliver because the description sheet said it will, is not the answer. I could go on and on about products that made claims but failed when applied. The manufacture will come up with an answer to serve THEIR end, and the consumer is the one to suffer.

There are two issues here...One is experience for which there is no substitute, and Two, is to read all the technical data provided for a product and arrive at what appears to be a logical and intelligent conclusion. If given the option, I’ll take the information spoken through experience any day.

Years ago I took the state test for a Michigan builders license. I remember one question on the test with regard to painting, it was, “what is the best product for priming new or existing wood”, since my experience with the Dupont primer, I responded with acrylic latex primer......it was the wrong answer according the state of Michigan. The correct answer was oil base primer.
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Old 05-31-2012, 08:47 PM   #19
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+ 1 on S&W Exterior Oil base primer on bare wood and sanded surfaces.
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Old 05-31-2012, 08:54 PM   #20
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Quote:
Originally Posted by spraygunn View Post
Lippy,

When I was contracting, the chemists didn’t come to me and tell me why this product was superior or not, or where the product was most effective, they asked my opinion as to how did it work, or were there any performance issues they should know about?

Most everyone here offering advise speaks from practical experience. We are all capable of reading product descriptions or MSDS sheets and derive a conclusion to a situation. However there is no substitute for experience in the field. We learn by doing and often times pay for that experience at our own expense. Assuming a product will deliver because the description sheet said it will, is not the answer. I could go on and on about products that made claims but failed when applied. The manufacture will come up with an answer to serve THEIR end, and the consumer is the one to suffer.

There are two issues here...One is experience for which there is no substitute, and Two, is to read all the technical data provided for a product and arrive at what appears to be a logical and intelligent conclusion. If given the option, I’ll take the information spoken through experience any day.

Years ago I took the state test for a Michigan builders license. I remember one question on the test with regard to painting, it was, “what is the best product for priming new or existing wood”, since my experience with the Dupont primer, I responded with acrylic latex primer......it was the wrong answer according the state of Michigan. The correct answer was oil base primer.
Hiya Spraygun...

I agree with you on the experience thing. Although I've applied quite a bit of product during my career, I'd never claim to be a better applicator of paint than a good painter is...but, application makes one an expert on application, not necessarily an expert on paint. Manufacturers must rely on the experiences of qualified painters for all those variables we may not consider when assembling the components of a gallon of paint - without your input, we may very well make a product capable of lasting several lifetimes, be bulletproof and cures cancer in the process of drying...but if you can't get it out of the bucket and onto the surface, it kinda loses some of it's appeal to the marketplace.

In that same vein, painters must rely on the expertise of manufacturers to deliver a product capable of performing, in a reasonably expected manner, and compatible with whatever exposure is presented at the time of application and beyond. To develop these products, to your application standards, in an ever changing environment of new and varied substrates, AND stay within the moving target guidelines of an ever-so-helpful regulatory government, requires just a tad bit of a scientific understanding of chemicals (and their reactions to one another) plus a pretty in-depth knowledge of the specific peculiarities of these new and varied substrates (and how they react with this compilation of paint components).

From those 2 comments, I'd say the painter and the manufacturer should be kinda mutually dependent on, and respectful of each other...(and btw, there are a few of us on this here forum that do a little more than just "read" a product's Tech Data Sheet and pretend to be more knowledgeable of products and application then they actually are...)

Getting back to topic...We could debate all day about whether Acrylic or Alkyds are the best thing to prime bare wood with - and there are equally convincing arguments to be made for both sides - when in fact, it's impossible to say one is better than the other from a general perspective. Alkyds work better in some instances, Acrylics in others. Your Michigan State test, that you took "years ago", asked a very vague, and outdated question about priming new or existing wood, but didn't specify the type or condition of the wood (necessary info needed to answer the question correctly) - nor whether it was plywood or not...which brings us back to Lippy's situation. Acrylics are flat out the better choice for exterior plywood - for all the reasons I mentioned in my earlier post.

Also, as a sidenote: Paintguy made a good point about alkyds/oils doing a better job of blocking out water soluble stains, and that's true (one of the advantages of alkyds), and that alkyd/oils penetrate deeper/better than acrylics. Also true, but that by itself may, or may not, be an advantage of alkyds. It's important to note that penetration is necessary for all oil/alkyd products to reach maximum adhesion, but not so true with acrylics. Acrylics "cling" very tightly to a surface and their adhesion (generally speaking) is on the borderline of phenomenal.
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Old 06-01-2012, 08:28 AM   #21
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I just want to highjack this thread for one moment with a couple questions for Ric - you mention there are circumstances where alkyds are more appropriate than acrylics - can you give some examples? What would be your recommendations for pre-primed cedar in the pacific NW? - how about board siding?
Hiya Windows...

Mr. Paint described an issue that seems common regardless what part of the country you reside...My experiences with pre-prime, or pre-stain applicators have been the same as his...most often times the application of paint, or stain, is too thin to provide an adequate foundation for anything but another coat of primer. However, I also agree with Mr. Paint that an acrylic, stain-blocking primer would probably be the best recommendation for your particular app.

To answer your other question of when an alkyd is more appropriate than an acrylic, a good understanding of each resin's strengths and weaknesses is necessary. Strengths: Acrylics have excellent adhesion to bare wood...Alkyds penetrate better than acrylics. Acrylics are more mold and mildew resistant than alkyds...Alkyds are typically better at blocking tannin staining (very common with redwood and cedar). Acrylics are better able to pass moisture through the film than alkyds. Weaknesses: Acrylics don't penetrate very deeply into a porous surface* ...Alkyds provides a food source for mold & mildew. Alkyds become more brittle over time (nature of the beast).

Because of their ability to penetrate a porous surface, Alkyds tend to perform a little better than acrylics on grey, weathered wood. The alkyd resin penetrates beyond the gray, dead fiber and sort of re-attaches, or binds, that fiber to the host board, creating a more stable foundation capable of holding finish coats of paint. I mentioned that straight acrylics don't really penetrate very well, so they're not really able to bind a loose, dead fiber solidly to the host board as an alkyd can. Acrylics will absolutely adhere to this grey fiber, but without a deeper penetration, the dead fiber will ultimately become detached from the host board, taking the surface adhering acrylic primer with it...This scenario may be accelerated by the application of an acrylic primer as acrylics shrink so much during the dry and cure time, they can actually "pull" the loose, partially detached, fiber from the host. In this case, it's kind of important to note that the acrylic product has stuck to what it was applied to, what it was applied to, (dead fiber), broke away from the host taking the prime and all subsequent coats with it - the evidence of that is all the grey fiber, tightly adhered, to the back of the paint chips.

So, after a long-winded blah, blah, blah...Generally speaking (very generally) Alkyds will perform better on weather wood, or woods extremely high in tannin acids...Acrylics will perform best on new, blond wood and exterior PLYWOOD.

Keep in mind that these are generalizations of acrylics versus alkyds. By modification, manufacturers are able to extend the flexibility of alkyd resins for longer periods of time - and - modify acrylics to provide better penetration by blending a variety of resins to create an acrylic capable of binding loose and foreign matter to board, plus introduce variant resins & pigments that are capable of better water-soluble stain blocking...

I don't know if that answered your question, and I hope this is more informative than confusing, but I kind of have that knack of confusing the $%&# out of people.

Last edited by ric knows paint; 06-01-2012 at 11:58 AM.
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Old 06-01-2012, 05:59 PM   #22
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I don't know if that answered your question, and I hope this is more informative than confusing, but I kind of have that knack of confusing the $%&# out of people.


Confusing? not at all
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Old 06-03-2012, 12:36 PM   #23
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For plywood products I use Pittsburgh's Permanizer Plus.

http://www.ppgpittsburghpaints.com/o...izer/index.htm
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Old 06-06-2012, 01:35 PM   #24
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For plywood products I use Pittsburgh's Permanizer Plus.

http://www.ppgpittsburghpaints.com/o...izer/index.htm
Permanizer is a great modified acrylic product - and a perfect example of what manufacturers are able to develop through creative modification.

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