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Discussion Starter · #1 · (Edited)
Wanted to help create a guide for this issue due to many misconceptions and highlight there is no universal hard rule for which product is best for your project.


1. Iron Shell Myth: Finish coats on exteriors need to negotiate the moisture and temp differences between the inside and outside of the home. A hard cured finish that does not allow the wood to properly breathe may look good from the outside but is damaging the wood by water collection and creating a cavity for mold and mildew.

2. Is solid stain and paint the same? No. If any company markets a stain that requires priming then they are really just selling you paint. They can be made using some of the same materials but the formulas are quite different which is why stain does not need to be primed.

There are key differences between the two products:

A. Paint requires a primer coat which puts a barrier between the wood and the paint impeding the ability of the wood to breathe.

B. Solid stain does not need primer.

C. Paint creates a fairly thick film over the wood which is why paint bubbles and peels. It does not allow the water vapor to escape so it basically explodes off the surface.

D. Stain does allow the wood to breathe much better allowing water vapor to escape much better than paint. There is a thin film but it is also more integrated into the wood because the resin value is different from paint and there is no primer coat.

E. Paint is stronger in terms of mechanical performance but in general this is moot unless your wife likes to use the siding as your face scrub.

F. Since the stain is not a filler nor holding a thick film it cracks less than paint because it contracts with the wood instead of in contention.

G. Solid stain should not peel. If it does your product is a poser because stain should not have enough resin to bind a film thick enough that can peel off. It can chip and flake but these are small in size (maybe an inch) and sporadic.

3. Homemade solid stain works great(!): Huge mistake. Adding a thinning agent does nothing to change the formula used to make the original paint.

4. Which product will last longer? This is a value question versus longevity which seems to be confusing for some people. Let's say two houses are coated, one with stain, one with paint. The stain fades away in 9 years and you need to recoat. The paint peels in 12 years and needs a recoat. Between the two projects, the stained house can be completed in the time it takes to prep the painted house and with almost half the material cost. The painted house has also created mildew issues around trim while the stained house has not, leaving the trim paint virtually untouched.

5. If your project is in a fairly dry climate and has good internal ventilation then paint would be a great choice as it will hold up longer than stain without causing the problems of trapped water and vapor.

6. I would never apply stain over paint or vice versa because it is too risky not knowing how the resins will interact. I know some stains say they can be applied over paint but again, the risk is too high. If you cannot put it on bare wood then stick with primer/paint. If a house is seriously bubbly show the client the numbers to prove removing the paint and applying stain is definitely the cheaper long term alternative.

7. Solid stain should fail a tape test. Since stain is designed to be malleable and not a mechanical bull it should always fail a tape test. This does not mean the product will fail to protect the siding. It only helps show how the stain is allowing the wood to breathe by not being a filler-blanket.

If you have applied solid stain in the past and it has failed it is probably due to a couple of common problems:

Applied over paint.

Applied to wood that has not been dry long enough. (I typically wait four to five days after any moisture exposure)

Used a stain that required primer, which is not really solid stain.

Applied on surfaces that contained a contaminate and usually some kind of cleaner, or the surface was not power washed at all.

Applied to a hardwood. (always a no-no.)

Applied to smooth wood.

Conclusion:

There are several factors to consider but generally true solid stain is the better choice simply because even when it is time for a recoat it can be done with much less money than with traditional primer and paint and unlike paint it does not cause relational problems with adjoining trim and other materials.

Another benefit I personally enjoy is the low temp application of 35 degrees. The most extreme test I did was spraying on Woodscapes in late January during a light snow. It was an east facing barn and the sun was very bright and warmed the surface very well so I sprayed it out and 7 years later still looks great.

Look forward to suggestions.
 

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Hair Splitter
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Wanted to help create a guide for this issue due to many misconceptions and highlight there is no universal hard rule for which product is best for your project.


1. Iron Shell Myth: Finish coats on exteriors need to negotiate the moisture and temp differences between the inside and outside of the home. A hard cured finish that does not allow the wood to properly breathe may look good from the outside but is damaging the wood by water collection and creating a cavity for mold and mildew.

2. Is solid stain and paint the same? No. If any company markets a stain that requires priming then they are really just selling you paint. They can be made using some of the same materials but the formulas are quite different which is why stain does not need to be primed.

There are key differences between the two products:

A. Paint requires a primer coat which puts a barrier between the wood and the paint impeding the ability of the wood to breathe.

B. Solid stain does not need primer.

C. Paint creates a fairly thick film over the wood which is why paint bubbles and peels. It does not allow the water vapor to escape so it basically explodes off the surface.

D. Stain does allow the wood to breathe much better allowing water vapor to escape much better than paint. There is a thin film but it is also more integrated into the wood because the resin value is different from paint and there is no primer coat.

E. Paint is stronger in terms of mechanical performance but in general this is moot unless your wife likes to use the siding as your face scrub.

F. Since the stain is not a filler nor holding a thick film it cracks less than paint because it contracts with the wood instead of in contention.

G. Solid stain should not peel. If it does your product is a poser because stain should not have enough resin to bind a film thick enough that can peel off. It can chip and flake but these are small in size (maybe an inch) and sporadic.

3. Homemade solid stain works great(!): Huge mistake. Adding a thinning agent does nothing to change the formula used to make the original paint.

4. Which product will last longer? This is a value question versus longevity which seems to be confusing for some people. Let's say two houses are coated, one with stain, one with paint. The stain fades away in 9 years and you need to recoat. The paint peels in 12 years and needs a recoat. Between the two projects, the stained house can be completed in the time it takes to prep the painted house and with almost half the material cost. The painted house has also created mildew issues around trim while the stained house has not, leaving the trim paint virtually untouched.

5. If your project is in a fairly dry climate and has good internal ventilation then paint would be a great choice as it will hold up longer than stain without causing the problems of trapped water and vapor.

6. I would never apply stain over paint or vice versa because it is too risky not knowing how the resins will interact. I know some stains say they can be applied over paint but again, the risk is too high. If you cannot put it on bare wood then stick with primer/paint. If a house is seriously bubbly show the client the numbers to prove removing the paint and applying stain is definitely the cheaper long term alternative.

7. Solid stain should fail a tape test. Since stain is designed to be malleable and not a mechanical bull it should always fail a tape test. This does not mean the product will fail to protect the siding. It only helps show how the stain is allowing the wood to breathe by not being a filler-blanket.

If you have applied solid stain in the past and it has failed it is probably due to a couple of common problems:

Applied over paint.

Applied to wood that has not been dry long enough. (I typically wait four to five days after any moisture exposure)

Used a stain that required primer, which is not really solid stain.

Applied on surfaces that contained a contaminate and usually some kind of cleaner, or the surface was not power washed at all.

Applied to a hardwood. (always a no-no.)

Applied to smooth wood.

Conclusion:

There are several factors to consider but generally true solid stain is the better choice simply because even when it is time for a recoat it can be done with much less money than with traditional primer and paint and unlike paint it does not cause relational problems with adjoining trim and other materials.

Another benefit I personally enjoy is the low temp application of 35 degrees. The most extreme test I did was spraying on Woodscapes in late January during a light snow. It was an east facing barn and the sun was very bright and warmed the surface very well so I sprayed it out and 7 years later still looks great.

Look forward to suggestions.
Sounds like you got it all figured out and have no room for any real suggestions or differing opinions. That is evident from the precious thread.
 

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This just made me realize I don't give a **** since 99.9% of my work is interior. But the next time I get a call for an exterior paint job I'll be sure to tell them the whole job has to be stripped and stained. And I guess I'll be filing a lawsuit against Cabot for selling me primer for under solid stains since that's just not possible.
 

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Hair Splitter
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This just made me realize I don't give a **** since 99.9% of my work is interior. But the next time I get a call for an exterior paint job I'll be sure to tell them the whole job has to be stripped and stained. And I guess I'll be filing a lawsuit against Cabot for selling me primer for under solid stains since that's just not possible.
It wasn't stain...didn't you read the OP.
 

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Are we talking latex or oil?

A few things. Every exterior latex stain is essentially paint. Period. Anything that forms a film is basically a paint.

If you mean oil stain, I hope the surface is beaten to death with a pressure washer and dry as he'll. Otherwise there will be drying, flashing, caulking and mildew problems almost immediately. Don't get me started on what the VOC laws have done to oil products.

There are a lot of generalities in the op that are misleading and wrong. I've seen oil stiain peel, I've seen latex paint last 20 years.

When you say "real" oil stain you mean a real long oil. Hasn't been available in 15 years.

Sickkens is the only one left that's even close.

I would like to know specifically which products you are referring to.

Given you wrote that entire post without mentioning a vehicle raises more than a few eyebrows.
 

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Discussion Starter · #11 ·
This just made me realize I don't give a **** since 99.9% of my work is interior. But the next time I get a call for an exterior paint job I'll be sure to tell them the whole job has to be stripped and stained. And I guess I'll be filing a lawsuit against Cabot for selling me primer for under solid stains since that's just not possible.
Do you realize Cabot product you are referencing is a stain? There are stain primers used for tannin bleed but they are not traditional primers and nobody said the whole exterior had to be stripped as I clearly laid out options.

You guys need to find a new gynecologist.
 

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Discussion Starter · #12 · (Edited)
Are we talking latex or oil?

A few things. Every exterior latex stain is essentially paint. Period. Anything that forms a film is basically a paint.

If you mean oil stain, I hope the surface is beaten to death with a pressure washer and dry as he'll. Otherwise there will be drying, flashing, caulking and mildew problems almost immediately. Don't get me started on what the VOC laws have done to oil products.

There are a lot of generalities in the op that are misleading and wrong. I've seen oil stiain peel, I've seen latex paint last 20 years.

When you say "real" oil stain you mean a real long oil. Hasn't been available in 15 years.

Sickkens is the only one left that's even close.

I would like to know specifically which products you are referring to.

Given you wrote that entire post without mentioning a vehicle raises more than a few eyebrows.
Given you had to ask if this was about water based or oil stains that raises several eyebrows.

I never said paint wont last 20 years and I never said stain is always better than paint.

Water based stains have a much lower level of resin which is why they do not need a primer, why they do not fill in gaps like paint, why they do not peel like paint, why they do not form a film like paint, why they allow wood to breathe better than paint, and why when it is time for a recoat there is very little prep involved compared to paint.

Where did I say "real oil stain?"

If you saw oil stain peel it is probably because it never had the chance to cure due to wrong application. Once oil is cured it chips, doesn't peel. Latex peels because....well...it is latex and plastics are quite malleable.

So far you have not pointed out anything false claim in the OP. If I made a false claim then state why. These responses of simply not liking it wont fly.
 

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Discussion Starter · #13 ·
He's probably too young to have ever used exterior oil stain. Too bad I can't give him some creosote to test.
I have some creosote in the garage. Not quite legal but it is a nice museum piece.

I would only use exterior oil stain on a hardwood. Instead of making assumptions about posters it may be more helpful to actually respond to the post and what was actually posted instead of looking for ways to complain.
 

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Wanted to help create a guide for this issue due to many misconceptions and highlight there is no universal hard rule for which product is best for your project.


1. Iron Shell Myth: Finish coats on exteriors need to negotiate the moisture and temp differences between the inside and outside of the home. A hard cured finish that does not allow the wood to properly breathe may look good from the outside but is damaging the wood by water collection and creating a cavity for mold and mildew.
I agree there is no hard rule for which product is best for every project. On to 1):

Areas that have routine water exposure and poor dying conditions may perfoprma very poorly with Woodscapes acrylic stain. Moisture content in the wood spikes during the exposure to water, and due to poor drying conditions, the moisture level may not come down fast enough to prevent rot. This is more than theoretical - I have some acrylic stained boards outside that I tore out with exactly this problem I'm saving to test different preservation / consolidation techniques. Alkyds, urethanes, and epoxies will keep the moisture content down in these situations, but they won't dry well to the outside.
 

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Discussion Starter · #15 ·
I agree there is no hard rule for which product is best for every project. On to 1):

Areas that have routine water exposure and poor dying conditions may perfoprma very poorly with Woodscapes acrylic stain. Moisture content in the wood spikes during the exposure to water, and due to poor drying conditions, the moisture level may not come down fast enough to prevent rot. This is more than theoretical - I have some acrylic stained boards outside that I tore out with exactly this problem I'm saving to test different preservation / consolidation techniques. Alkyds, urethanes, and epoxies will keep the moisture content down in these situations, but they won't dry well to the outside.
My experience has been the stain works well in these areas (on softwood only) so long as it was correctly applied and allowed to cure. The stain allows for much more air movement than paint so instead of the moisture getting trapped between the wood and the paint it allows it to escape preventing the topcoat from being pushed out.

This is all kind of tough since I cannot see your examples and know all the details but I do know if siding is constantly always wet to some degree then any topcoat is moot because the problem lies with the ventilation of the house.
 

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A. Paint requires a primer coat which puts a barrier between the wood and the paint impeding the ability of the wood to breathe.

B. Solid stain does not need primer.

C. Paint creates a fairly thick film over the wood which is why paint bubbles and peels. It does not allow the water vapor to escape so it basically explodes off the surface.

D. Stain does allow the wood to breathe much better allowing water vapor to escape much better than paint. There is a thin film but it is also more integrated into the wood because the resin value is different from paint and there is no primer coat.
I'll use SW acrylic Woodscapes and SW Superpaint for the purposes of commenting, but I'm not saying either are the best in their coating class.

Both the stain and paint dry to similar mil thicknesses. The stain does use a different mix of polymer lengths, as well as a ~2X larger amount of VOCs. On the right substrate with the right prep, either can be used with no primer with good results (I've used both of these products with no primer). On the wrong surface, they both need primer or they will both peel.

Permeability of the acrylic polymer would be in the same ball park for both these coatings. The fillers, however, are not permeable at all. Solid tints aren't permeable either, but that isn't much of an issue in most cases. Permeability of the dried film is pretty much set by the fillers / tint. If you used flake aluminum for the filler in a stain, it would have horrible permeability.

On to penetration / surface consolidation. The shorter chain acrylic polymer with higher VOCs would be expected to give better penetration into the wood compared to the acrylic paint. I haven't measured it, but my observations make me think this does occur. The greater the penetration, the better it is bonded to the wood, making it more difficult for it to flake off the surface.

Acrylics, however, don't penetrate as well or consolidate the surface as well as a traditional oil based primers. Here. I'm talking about the old, slow drying primers from back in the 70s, for instance. This is an advantage on a heavily weathered surface, where you may have significant degradation of the wood fibers. Putting acrylic paint on that (no primer), only the surface fibers get locked into the coating, and these are relatively easily separated from the underlying fibers. That will blow off the wall pretty easily. Solid stains penetrate more, so they won't blow off the wall as easily, but unless they penetrate enough to get past the degraded fibers, they still blow off the wall. In either of these situations, the next better thing to do is use an oil based primer. I used to use A100 oil based primer for this. Adhesion was better, but still wasn't as good as the 70s oil based primers. Those were runny, very low filler, slower drying and penetrated very well. Essentially, these were used as primer / sealers.

Coating breathability on an old house is somewhat overrated. They were painted with oil paints for 100-200 years without a breathability problem. Typically, moisture / drying issues in these buildings are caused by poorly thought out retrofits, heating system changes, and poor maintenance. In dealing with an old house that has blown in insulation retrofitted, drying is seriously impaired in all directions, so keeping moisture levels down on the inside and keeping exterior water from entering the wall system is my preferred approach, otherwise you're begging for rot issues somewhere in the wall system. Using a vapor permeable coating on the exterior to allow significant drying to the outside just may not be a good way to compensate for other problems.
 

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My experience has been the stain works well in these areas (on softwood only) so long as it was correctly applied and allowed to cure. The stain allows for much more air movement than paint so instead of the moisture getting trapped between the wood and the paint it allows it to escape preventing the topcoat from being pushed out.

There's a reason why acrylics aren't used on wooden skiffs, canoes, kayaks, just to give an extreme example. Prep it all you want, let the acrylic stain or paint cure all you want. Then put it in the water for a few hours, take it back out for a while, put it back in, etc. You get the idea. Unless the wood is rot resistant to begin with, it WILL rot. There are two different things involved - how vapor permeable the film is, and how fast liquid water will travel through it. If the vapor permeability can't keep up with the load you get from liquid water exposure, it's doomed. Same thing comes into play with house wraps - that's why looking at the two numbers (not just vapor permeability) is important.

The correct way to apply acrylic stain or paint in those situations is dump it on the ground.
 

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Discussion Starter · #18 ·
There's a reason why acrylics aren't used on wooden skiffs, canoes, kayaks, just to give an extreme example. Prep it all you want, let the acrylic stain or paint cure all you want. Then put it in the water for a few hours, take it back out for a while, put it back in, etc. You get the idea. Unless the wood is rot resistant to begin with, it WILL rot. There are two different things involved - how vapor permeable the film is, and how fast liquid water will travel through it. If the vapor permeability can't keep up with the load you get from liquid water exposure, it's doomed. Same thing comes into play with house wraps - that's why looking at the two numbers (not just vapor permeability) is important.

The correct way to apply acrylic stain or paint in those situations is dump it on the ground.
For the skiffs, etc the whole idea is to prevent any transfer of water and Im not sure how those examples are compatible with this discussion as the purpose of topcoats on wood siding is to allow the wood to breathe.

For solid stains there is little film compared to paint which is why it allows the wood to breathe better and allow vapor to pass through. This all of course is based on the assumption the house has the proper wrap/rain screen, etc. Topcoats can never be used as a problem solver regarding structure ventilation.
 

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Discussion Starter · #19 ·
I'll use SW acrylic Woodscapes and SW Superpaint for the purposes of commenting, but I'm not saying either are the best in their coating class.

Both the stain and paint dry to similar mil thicknesses. The stain does use a different mix of polymer lengths, as well as a ~2X larger amount of VOCs. On the right substrate with the right prep, either can be used with no primer with good results (I've used both of these products with no primer). On the wrong surface, they both need primer or they will both peel.

Permeability of the acrylic polymer would be in the same ball park for both these coatings. The fillers, however, are not permeable at all. Solid tints aren't permeable either, but that isn't much of an issue in most cases. Permeability of the dried film is pretty much set by the fillers / tint. If you used flake aluminum for the filler in a stain, it would have horrible permeability.

On to penetration / surface consolidation. The shorter chain acrylic polymer with higher VOCs would be expected to give better penetration into the wood compared to the acrylic paint. I haven't measured it, but my observations make me think this does occur. The greater the penetration, the better it is bonded to the wood, making it more difficult for it to flake off the surface.

Acrylics, however, don't penetrate as well or consolidate the surface as well as a traditional oil based primers. Here. I'm talking about the old, slow drying primers from back in the 70s, for instance. This is an advantage on a heavily weathered surface, where you may have significant degradation of the wood fibers. Putting acrylic paint on that (no primer), only the surface fibers get locked into the coating, and these are relatively easily separated from the underlying fibers. That will blow off the wall pretty easily. Solid stains penetrate more, so they won't blow off the wall as easily, but unless they penetrate enough to get past the degraded fibers, they still blow off the wall. In either of these situations, the next better thing to do is use an oil based primer. I used to use A100 oil based primer for this. Adhesion was better, but still wasn't as good as the 70s oil based primers. Those were runny, very low filler, slower drying and penetrated very well. Essentially, these were used as primer / sealers.

Coating breathability on an old house is somewhat overrated. They were painted with oil paints for 100-200 years without a breathability problem. Typically, moisture / drying issues in these buildings are caused by poorly thought out retrofits, heating system changes, and poor maintenance. In dealing with an old house that has blown in insulation retrofitted, drying is seriously impaired in all directions, so keeping moisture levels down on the inside and keeping exterior water from entering the wall system is my preferred approach, otherwise you're begging for rot issues somewhere in the wall system. Using a vapor permeable coating on the exterior to allow significant drying to the outside just may not be a good way to compensate for other problems.
Superpaint is ok but I rarely use that for trim or anything else and I would never apply paint w/o a primer as Ive never seen it succeed.

Older homes were constructed with higher quality materials and craftsmanship which allowed for greater room in choosing a topcoat because there was not as much vapor passing in such large areas. If people ask about buying a house I always recommend looking for one built prior to 1970 because even if deleading is necessary the long term maintenance cost will be cheaper.
 
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