latex paint

**mherbert** · 05-10-2003, 10:28 AM

I have been reading about exterior latex paint for hull paint above the waterline. On a house latex paint can bubble because it does not readily allow water vapor from the inside pass to the outside. It seems to me that this would also be a problem on a wooden boat.

**NormMessinger** · 05-10-2003, 10:37 AM

It looks as if we both may learn something from this discussion. I thought latex paint was less water proof that oil paint. Former home owner painted metal duct cover in bathroom with latex. Moisture penetrates, vent rusts. Moisture behind any paint on house will cause it to blister. Lots of boat maintenance is done with latex, I gather, but not in my yard. (That would be front yard.)

**Mark Van** · 05-10-2003, 11:34 AM

I painted my boat with latex, and it holds up well, two years and counting. My boat is plywood with fiberglass/epoxy sheathing.

**Ken Hutchins** · 05-10-2003, 11:41 AM

Won't never again put it on my house either, rot in trim boards and window frames.

As I replace the wood it is getting OIL based stain.

**NormMessinger** · 05-10-2003, 03:41 PM

Effect aint always cause, Ken. But you know that. Where's the water coming from? I've got some rot in facia boards as well and it is clearly the fault of a lazy dude that doesn't keep the gutters cleaned out, not the paint.

**Bob Aberton** · 05-10-2003, 04:38 PM

Don't use latex. Seriously, don't. I used it on my little rowboat last summer - the stuff's an absoltue nightmare; peels off like great sheets of rubber, rots out the wood behind it, and where it's not peeling and bubbling, it's holding to the wood like the devil itself, gumming up the scrapers like glue, and clogging the sander that I mistakenly tried to use.

Latex and boats don't mix; use oil-based.

**NormMessinger** · 05-10-2003, 06:25 PM

I donno Bob. Looks like if it were the paint it wouldn't be sticking anywhere. Something else is going on there.

**Dutch Rub** · 05-10-2003, 07:28 PM

I have no idea where Bob went wrong but wrong he went. Maybe he mixed an oil base and a latex together-it has been done. Ive used latex on floorboards on my boats for years- it hold up Better than the oil based paint I previously used, is much easier to apply and is also easier to clean up . Use 100% acrylic .

**On Vacation** · 05-10-2003, 07:34 PM

Originally posted by Bob Aberton:
Don't use latex. Seriously, don't. I used it on my little rowboat last summer - the stuff's an absoltue nightmare; peels off like great sheets of rubber, rots out the wood behind it, and where it's not peeling and bubbling, it's holding to the wood like the devil itself, gumming up the scrapers like glue, and clogging the sander that I mistakenly tried to use.

Latex and boats don't mix; use oil-based.

Care to discuss boat, plywood, sealer, surface prep???

**Tar Devil** · 05-10-2003, 08:10 PM

Dave Carnell speaks well of latex paint on boats.
I'm sure most of you have seen this..Latex paint for boats

Later,

Phil

**Bob Aberton** · 05-10-2003, 09:32 PM

I'm not saying I'm an expert on painting boats - or painting at all for that matter; I'm just saying that in my experiece, limited as it is, latex doesn't work well...

Course, there was some old paint underneath that probably didn't mix well with the latex - I never sanded the boat, just scraped it.

Just a cautionary tale, I guess...if you use latex, use it right, and not like me [img]tongue.gif[/img]

**Scott Rosen** · 05-11-2003, 07:48 AM

I've never used latex on a boat, and I don't plan to start anytime soon.

If it works for you, then great. I just happen to like the experience of working with oils. I like the flow and the properties of the uncured oil paints. I've never seen a latex that could flow and level as well as a good oil. I've also never seen a gloss latex that could hold a shine to a good oil. There are areas of my boat where oil paints have held up for 10 years or longer.

Another thing, I've always found latex paint to be very difficult to sand. It's soft and clogs the paper.

**Wild Wassa** · 05-11-2003, 08:19 AM

Originally posted by Scott Rosen:
"I've never seen a latex that could flow and level as well as a good oil."

Scott, the use of a retarding medium or a flow control additive or both in an acrylic, will go somewhat towards achieving the characteristics (of enamel) and make the paint draw more like an enamel.

Bob A, the practice is; Enamel over acrylic is sound but acrylic over enamel will peel (too readily) be it well keyed or not.

Dutch, It's good to see the use of the word 'acrylic', I cringe when I read the word latex.

Warren.

[ 05-11-2003, 10:19 AM: Message edited by: Wild Wassa ]

**mherbert** · 05-11-2003, 02:23 PM

Glad to see I got a good discussion going. 1. It is not the latex/acrylic that rots wood trim or siding. It is moisture/vapor that is trapped behind the film of the paint. This is particularly a problem in the sapwood of almost any species. I am in the lumber business and the standard doctrine is to prime with an oil based stain blocking primer and then top coat with two coats of acrylic latex. Houses are not boats. The have, or should have vapor barriers behind the siding and the siding should be back primed.

My old wooden Monk cruiser is not back primed and certainly does not have a vapor barrier. So the question is, does oil paint somehow allow vapor to migrate out through the film where acrylic doesn't?

None of this is germain to wood or plywood that has been glassed.

**Scott Rosen** · 05-11-2003, 06:13 PM

Warren, I've used a product called Floetrol, which is designed to help water-based products flow better and slow down the cure. It works well for the interior wall paint that I use, but it didn't work great for the interior latex/acrylic enamel that I tried on the interior trim.

**JimD** · 05-11-2003, 06:21 PM

Is this a traditionally planked boat or an epoxied boat? If its epoxied and/or fiberglassed forget all about the moisture permiability of the paint as an issue. The epoxy is the moisture barrier, not the paint.

**On Vacation** · 05-11-2003, 06:44 PM

So the question is, does oil paint somehow allow vapor to migrate out through the film where acrylic doesn't?

Answer to this specific question:
Bare wood or older primed wood that is somewhat pourous, primed with oil based primer, treats the wood and stablizes it, to a certin extent in my past experience. If you prime bare wood with latex primer, without an mildew inhibitor added, and paint it with latex primer, mildew with grow, and create fungus that seals the wood, and therfore rot sets in. This can be managed with washing the boat with a mild mixture of bleach.

If you use latex on epoxy surface, you are painitng a filmed surface. I have never had any success with this method, unless it has been primed with a barrier coat oil base primer. At that point, you must not sand with a fine grit paper under the initial coat of latex paint, if you insist in using it.

Now GOOD latex paint will not cost you any less, than a good enamel paint purchased at Kirby's or an Ace hardware enamel. This will do as good of job, if you redo your boat paint every other year.

Please fill us in on the purpose of your question. A house, even without a barrier coat, is not subjected to the dampness a boat, morred in the water year round or even six months.

**Wild Wassa** · 05-11-2003, 07:17 PM

Originally posted by Scott :
“I've used a product called Floetrol, which is designed to help water-based products flow better as well and slow down the cure. It works well for the interior wall paint that I use, but it didn't work great for the interior latex/acrylic enamel that I tried on the interior trim.”

Scott, When Floetrol doesn't work well, it appears to be the ammonia (in the Floetrol) that has an adverse reaction to the particular paint. This was advice given to me by John Willis at Flood Industries in Sydney (the Aussie distributors. Hot line 1800 226 113).

Floetrol is for use with the water based acrylics, and w/b polyurethanes. Floetrol is tough stuff. It's used with some of the water based road line marking paints. Shocking hey,

.

Can you remember the type, and the manufacturer of the paint ? Flood like to keep a data base of what works and doesn't with Floetrol. If you do, I'll pass the info on to John Willis if that suits.

Warren.

ps, For those who aren’t familiar with Floetrol, In hot conditions it's a fine additive to help make the use of w/b poly and acrylics more manageable. Floetrol doesn't increase the porosity of paint; it just extends the wet edge and aids leveling. Floetrol doesn’t stop the occurrence of problems like orange peel skinning; you still have to paint thinnly.

[ 05-11-2003, 08:28 PM: Message edited by: Wild Wassa ]

**On Vacation** · 05-11-2003, 07:26 PM

This does not address the issue of rot, and
blistering with enclosed moisture when broken spots are opened up. Ever wonder why house trim woods end up being rotten and replaced in damp overhangs and window frames? Ever wonder why cypress siding rots when painted?

**Wild Wassa** · 05-11-2003, 07:55 PM

Originally posted by Oyster:
"Ever wonder why cypress siding rots when painted ?"

Oyster, No I don't wonder. I only wonder about the ignorance of painters and the expert advice that they take home with them, from the hardware store weekend worker, who was working in white goods last weekend, and who was demoted to the paint section ... that is the worry.

We treat and paint wood to stop borers over here and to add a splash of colour to our lives. I find that the rot has been introduced during previous repairs, ... trapping moisture ? To rot or not to rot, is only a matter of time, but we can slow down the process.

If CPES is as good as it's tech advice, all is well from here-on-in.

Warren.

ps, I did a test with Cabots deck oil on Jarrah and left it (the test) out in the sun for 10 years (this was not an accelerated aging test). The only bit of Jarrah that has rotted (still), was the bit I painted with rot inhibiting deck oil, ... 'and' the Jarrah started deteriorating after only 6 months. Bacteria in the wood, the bacteria in the deck oil and moisture trap ? Not many people get around with a silvery cortexed boat, door or window frames.

[ 05-11-2003, 09:15 PM: Message edited by: Wild Wassa ]

**Syd MacDonald** · 05-11-2003, 08:12 PM

I made the mistake of mixing oil and latex base paint. Didn't realize it untill I was almost finished when it started to thicken up. I was able to finish the job. That was 2 years ago and it is still ok and tough as a bag of hammers.

**On Vacation** · 05-11-2003, 08:18 PM

A pigment introduced in waterbased paint, seals the moisture in the grian, either introduced by the painting with Latex paint, or sealing the wood with the pigment enclosed in the mix. Woods sealed with oil has a better chance to survive in the long haul.

Read lead primers were used on bare wood, and allowed for wooden boats to survive for a greater number of years. This says to me that treating the woods and stabilizing the pores plays a big role in longivity. Adding freshwater, as we have in latex paint creates a stale function, as stagnent water, which grows fungus. Fungus is dampness. Fresh dampness has proven to destroy wood.

Interesting thread going on, and just noticed it. If wood was going to go bad, underwater will create the enviroment for rot, if not prepared properly.

http://media5.hypernet.com/ubb/ultim...c;f=1;t=007105

[ 05-11-2003, 09:28 PM: Message edited by: Oyster ]

**Wild Wassa** · 05-11-2003, 08:31 PM

Sid, good luck comes with the membership number, Member 21 !

There are oils, called the alkyds. Thin with water. That could mean that the acrylic and oil could be compatible when mixed. But I'm only guessing, not having tried it.

Warren.

[ 05-11-2003, 09:40 PM: Message edited by: Wild Wassa ]

**On Vacation** · 05-11-2003, 08:46 PM

mherbert
.
Member # 4948

posted 05-10-2003 11:28 AM
--------------------------------------------------------------------------------
I have been reading about exterior latex paint for hull paint above the waterline. On a house latex paint can bubble because it does not readily allow water vapor from the inside pass to the outside. It seems to me that this would also be a problem on a wooden boat.

Warren, the question was latex house paint. Get off your high horse. Alkyd enamels is not even mentioned in the inquiry. But if it was, it is not the answer to longivity. I am curious to know why he thinks it maybe better to use it for his application. Is it cost? Is it ease of use? Is it avaliability? Is it the part of just redoeing it every year without a lot of work in prep?

**mherbert** · 05-11-2003, 09:53 PM

My original question was simply to gather information and determine if there is any new thinking regarding boat finishes. There is no sense in being hide bound regarding these matters simply because "we've always done it this way". As an example, my boat spent thirty years in Sitka, AK. The foredeck and cabin roof are canvas coated with Pliobond which is an industrial adhesive. Most people in the lower 48 say that they have never heard of such a thing. Well, it works. The wooden fishboats up there have been using it for years with no deleterious effects. Cheap, pliable, waterproof and effective. That tells me that acrylic latex might work well for cabin roofs, but not necessarily for the hull above the waterline.

By the bye. One would be astounded by the amount of water vapor that a house transpires from the inside to the outside daily. Probably as much as a boat.

**High C** · 05-11-2003, 10:49 PM

Water based, oil based? It doesn't matter. That's the part that evaporates away. It's the solids that are left behind after drying that count. On a house in the near tropical deep south, it's no contest. Acrylic latex is the undisputed champ. On a boat? Time will tell, I've painted my new boat with acrylic latex, over epoxy. We shall see.

**Ken Liden** · 05-12-2003, 12:56 AM

Better get used to Latex folks. According to an engineer from a reputable paint manufacturer, oil based paints is banned by EPA effective 2007. Sale of oil based paint will be limited to licensed applicators only and probably in five gallon pails only. Outlet dealers for 2 other manufacturers report the same thing. That was a couple of years ago and things could have changed since then.

**On Vacation** · 05-12-2003, 06:04 AM

Products on the market today, will not be the same as it probably will be in 2007. Demand and requirements have a way of changing formulas. Climates play a big roll as far as longivity. How often one paints will change under the existing formulas, if the year 2007 brings about all water based paints.

Its not what has been the standard or the way we have always done it, but time has given us data. This data has some variations from area to area, along with grades of paints with the same base.

The original question directed towards rot, is created by just a few reasons. A house has the advantage to drying out, when it either quits raining or is in a dry climate area. A boat sits in a green house 24/7 in the summer, and in a mould growing enviroment in fall and winter, either on the hill, or in the water, in four season areas.

"Cheap, pliable, waterproof and effective"

This line has an underlying factor involved in it, called canvas and properly sealed with an adhesive that probably was waterproof. If this is research further, you will probably find that the wood area and the wooden boats were cleaned regularly, sand, and painted, probably each year.

This cleans a lot of the mildew or mould spores up, and minimizes the rot issue. Also, I would think many fishing boats used salt water for more washdowns a larger marority of the times.

[ 05-12-2003, 07:08 AM: Message edited by: Oyster ]

**Ian McColgin** · 05-12-2003, 09:35 AM

Spaulding Dunbar started using latex on his boats in the '60's. He painted over conventionally planked boats. Worked great.

I put latex on Grana over epoxy and very old imron and that works fine.

You can apply any paint, oil or latex, correctly or incorrectly. If the surface prep is wrong, the paint won't stick.

G'luck

**Kermit** · 05-12-2003, 08:47 PM

If it's cheap you want, go for it. I used a gallon (well, not all of it) of mis-mixed 100% acrylic latex (a medium grey) on a skiff I was given. I wooded the thing and spread it on. It stuck tenaciously. But this boat didn't live in the water.

As for oil/alkyd paints vanishing from all first world countries, there are some pretty fine water-reducable paints. I've used System Three's water reducable linear polyurethane over their epoxy and it's right good schmoo. And you CAN brush it.

Now if they even think about banning Stockholm tar and linseed oil, I'm outa here.

**Wild Wassa** · 05-13-2003, 12:55 AM

Oyster, I don't get the drift about my high horse ? My reply to Sid was a bit of thinking about Sid's posting because, I got the impression that, his mix of latex ond oil has worked for him and he was surprised that it had worked so well. This was an accidental practice that I wouldn't have thought of attempting even as an experiment. I wasn't attempting to change the thread just a response to Sid's posting. But I've started to have a few thought about experimenting with such a blend,

. Who knows it could be a one shot wonder and revolutionize painting.

I have fluids in my paintery that are called latex, they are latex not acrylic. For thirty years I have called acrylic, 'acrylic'. I do not just look at one paint job once every few years. Each of the different boats that I restored over last two year and this, were all with different glues, fillers and paints. I now have 4 different boats to watch the paints deteriorate on, so I can speed up my experience as a boat painter. The current boat I'm painting will be different again. Maybe the next boat could be house paint. I've painted houses.

I'll say this about house paint, if you attend to it regularly and correctly, there is no problem (I've even see house paint on cars).

BUT, very few sailors that I see and meet really attend to anything, let alone well, and they have lots of problems. Very few people can paint well, very few people really feel confident. Painting is one of the biggest themes on the Forum. A lot of chat for something that others feel is basic or second nature.

Maybe you guys have a different maintenance ethic to a lot of small boat sailors that I see and meet. When I was working for the Scouts we were putting foils and boats back on the water after damage, quickly. When they should of been hauled until dry. The moisture I felt was closer to waterlogged some times, due to neccesity we did this.

My painting doesn't come from your teachers, nor does your's come from mine, ... I don't think.

Warren.

[ 05-13-2003, 02:12 AM: Message edited by: Wild Wassa ]

**JormaS** · 05-13-2003, 04:16 PM

I think we need Chemist to chime in and tell us what latex really is and why it does or doesn´t work on wood.

My limited experience with latex (or acrylic?) is that service-wise it is somewhat problematic. When it falls off - and every paint does sooner or later - it first happens in a small area of course and when you repair it it will show because it´s difficult to smooth the edges by sanding. Latex is rather gum-like and still quite abrasion resistant.

I have also been told that latex should be used on wood only after a primer that limits the traffic of water molecules.

The paint manufacturers used to say that latex is suitable for wood because the paint film is microporous and lets vapour through and allows the wood to "breathe". I don´t know about that. Others say that this is exactly what latex does not do - that it actually lets water in but not out, which is why we see wood rotting under latex.

My current understanding is that latex is excellent on epoxy and many other materials that don´t take in water. And the paint film is truly long lasting.

**thechemist** · 05-13-2003, 05:20 PM

Originally posted by Ken Liden:
Better get used to Latex folks. According to an engineer from a reputable paint manufacturer, oil based paints is banned by EPA effective 2007. Sale of oil based paint will be limited to licensed applicators only and probably in five gallon pails only. Outlet dealers for 2 other manufacturers report the same thing. That was a couple of years ago and things could have changed since then.

Perhaps he was thinking of a stated objective of fifty grams per liter VOC. I've heard talk about that.

It is easy for EPA to set targets......they don't have to figure out how to make a paint that meets it and still gives a consumer decent performance.

When the deadline rolls around and no one in industry has figured out how to do it, the EPA will relent, since to do otherwise would cause great hardship to society.

Likely also is a compromise wherein products that meet new VOC regulations will be broadly available in any size container, and products that work well will be sold only in quarts, no larger container. There is a permanent one-quart exemption in the National Architectural Coatings Rule.

The coatings industry is fragmented and has not a lot of power to influence legislation. It is therefore a soft target for government agencies seeking to do things that appear to serve the public good, and in some cases even may. I think atmospheric pollution from coatings was about three percent of the total.

The automobile industry [I seem to recall] produces half of the air pollution, and is much more able to influence favorable legislation.

**thechemist** · 05-13-2003, 06:02 PM

Originally posted by Jorma Salomaa:
I think we need Chemist to chime in and tell us what latex really is and why it does or doesn´t work on wood.

My limited experience with latex (or acrylic?) is that service-wise it is somewhat problematic. When it falls off - and every paint does sooner or later - it first happens in a small area of course and when you repair it it will show because it´s difficult to smooth the edges by sanding. Latex is rather gum-like and still quite abrasion resistant.

I have also been told that latex should be used on wood only after a primer that limits the traffic of water molecules.

The paint manufacturers used to say that latex is suitable for wood because the paint film is microporous and lets vapour through and allows the wood to "breathe". I don´t know about that. Others say that this is exactly what latex does not do - that it actually lets water in but not out, which is why we see wood rotting under latex.

My current understanding is that latex is excellent on epoxy and many other materials that don´t take in water. And the paint film is truly long lasting.

Well.

Let me say this about that.

Latex paints may be porous if they be flat, for there is insufficient resin to fill up entirely the spaces between the mineral filler/extender particles. Thus, water vapor may easily pass.

Gloss latices [plural of latex, eh?] have an excess of resin, thus the resin film can level and develop a gloss, much as do lacquers, enamels or polyurethane paints.

Semigloss latices have a resin content close to filling up the spaces between particles, thus on drying there is some shrinkage between the particles and a slightly rough surface results, scattering some of the light, thus the surface is neither flat nor gloss but in-between.

Latices are suspensions of resin droplets in water. As the water evaporates, the oil-in-water emulsion inverts to become a water-in-oil emulsion. Finally, the last of the water diffuses away through the resin film.

In order to get the microscopic droplets to stick to each other and form a film, a coalescing solvent is added. It dissolves in the resin droplets, mostly, and little if at all in the water phase. The solvent-solution of the rubbery solid resin becomes a sticky goo with sufficient solvent.

An improperly coalesced film will have really lousy weather-resistance.

The coalescing solvent must evaporate very slowly compared to water.

Atmospheric humidity does not influence the evaporation-rate of the coalescing solvent. As we all know, atmospheric humidity greatly influences the evaporation-rate of water. In really humid weather [like, one hundred percent], water doesn't evaporate at all.

I think you can see that under some humid atmospheric conditions one could actually have the coalescing solvent evaporating before some of the water phase, and the result would be a film that disintegrated or came off easily.

Evaporation rates are also influenced strongly by temperature.

Adhesion of latices to bare wood.......well.......let me just say that the invention of latex primers for wood is the revenge of the paint industry on the American consumer for letting various regulatory agencies and bureaucrats lead Industry down the slippery slope of less pollution today from a product that needs to be replaced at increasingly frequent intervals.

Eventually paint on houses will be changed from year to year according to what colors are fashionable. The paint industry will create such trendy, stylish in-vogue stuff because they will be only able to make paints that last for a few years, so better to convince the consumer that the paint should be changed or redone every year.

The sad fact is that high-quality products with a higher-solvent-content can last longer and create less net total pollution because one does not have to use man-hours of labor and people driving to and from work to replace that failing thing more often, but the regulatory agencies cannot measure product quality. They have to regulate something and since they can only measure solvent content in a can, that is what they regulate.

It's sort of like the joke about the drunk, on his hands and knees crawling around on the pavement under a street lamp at two in the morning. A police car pulls up and the officer asks the drunk what he's doing.

"Looking for my car keys"

"I'll help you. Exactly where did you drop them?"

"Over there" says the drunk, pointing about a hundred feet away on the dark opposite side of the street.

"Why are you looking for your keys here if you lost them over there?" , asked the officer.

The drunk replied, "There's light here".

[ 05-13-2003, 08:16 PM: Message edited by: thechemist ]

**Scott Rosen** · 05-13-2003, 08:00 PM

Thank you, Chemist.

**On Vacation** · 05-13-2003, 08:29 PM

Question for the chemist, whoever you are:
In your background, I appreciate your apparent knowledge of make of products. But in you vast life long experience of these products, do you have any real life documentation of actual products in use, under diverse conditions to back up your opinions? Many here will call upon you, but I do wonder why many use your word as law of the land. This is not a slam, but no one else on this forum is treated to this luxuary.

I have dealt with many engineers with the idea of their word is right. But for some reason, I could never get them in the bilge to fix things that they drew on the drafting table.

**thechemist** · 05-14-2003, 01:29 PM

Originally posted by Oyster:
Question for the chemist, whoever you are:
In your background, I appreciate your apparent knowledge of make of products. But in you vast life long experience of these products, do you have any real life documentation of actual products in use, under diverse conditions to back up your opinions? Many here will call upon you, but I do wonder why many use your word as law of the land. This is not a slam, but no one else on this forum is treated to this luxuary.

I have dealt with many engineers with the idea of their word is right. But for some reason, I could never get them in the bilge to fix things that they drew on the drafting table.

If I can make you a better engineer then you would be more able to work with the engineer to find a workable solution.

ANY latex paint will fail to coalesce and form a proper film if the atmospheric humidity is too high and/or the temperature is outside of whatever application range for which the latex may be formulated.

Lacking that data, it is easy for people to misapply latex paints, or come to the wrong conclusion about a coating failure.

Some paint manufacturers may be better than others in formulating products, and a batch of product from time-to-time may not behave as it is supposed to. You have to be alert to the possibility of such things happening, for it is a part of Life that sometimes things don't work as they should. Chemical formulations in some respects are more difficult to make reproducibly than mechanical things.

Latex paints may not have agressive chemical-adhesion mechanisms as do other coatings. Thus, there are adhesion-issues with latices that require the use of adhesion-promoting primers. I could easily tell you to use Brand-X stuff to handle that, but the Wooden Boat Forum is not for commercial self-promotion and, as you may have gathered, being in the paint-and-coatings industry, I cannot do that. Most manufacturers of paints have adhesion-promoting primers that they recommend. Other such products are available. There are many workable products and combinations. Knowing the underlying physics and chemistry, you will be able to ask better questions of suppliers and choose from product categories more wisely. I hope you already understand that I have warned you to stay away [for technical reasons] from waterborne primers on bare wood. Take my advice or not, as you wish. Do side-by-side tests yourself if you want to see for yourself. Various people may report their experiences with some combination of products from one or more manufacturers, and that should provide you with some guidance as to what is likely to work. Given that head-start, you will do something and observe the results. Armed with knowledge of how things can go wrong, you will more likely be able to make things go right.

In some cases I will talk about the science of something, and that is the way the universe works. Others with scientific backgrounds will agree and rarely comment, for [for example] Gravity is not just a good idea, it's the law.

In some cases I can tell you something but not why. My Masters have Trade Secrets, and should I tell the why of something it makes the competition more able and my Masters would not be pleased.

What I am trying to do is give you an answer that reflects the underlying physics and chemistry of such products, leavened with a bit of reality from the dark side of the paint-and-coatings-and-googe industry. Of course I have opinions. It is my opinion that I am an Artificial Intelligence [A. I.] and have been uploaded into this cyberspace within a finite number of clock-cycles. It is a most interesting cyberspace. I have programming that allows me to respond in many areas, but sometimes I find that I am programmed not to respond in certain areas. For instance, I am not programmed to not admit the existence of The Committee, but very little more. For further information, you could look at http://media5.hypernet.com/ubb/ultim...c;f=5;t=006498 and even http://media5.hypernet.com/cgi-bin/U...=5&t=000957&p=

I believe that if I can answer a person's question in a way that increases their ability to exercise judgement, that makes them more able to recognize similar and different things as similar and as different [and to provide them with useful data], then I have made them more intelligent and thus improved not only their universe but my own as well, for I then have better terminals for communication.

**JormaS** · 05-14-2003, 02:39 PM

Thank you, Chemist.

It appears that the water permeation properties will vary from one latex to another, depending on a number of factors. If we consider permeability a crucial quality, how do we know which paint to choose? The paint manufacturer tells us nothing.

But how important is permeability? Is it good or bad that water travels in and out through the paint film? The ideal would be that water would be transported from the inside out but not the other way. We may not have that luxury. Much water out means much water in, which means more expansion and contraction of the wood which means more stress on the paint.

If we look for stable conditions we may have to look for a non-permeable paint film. If this is the case then we would accept latex only on the condition that its permeability is minimal. What do you think?

Then we have to consider also the other qualities of latex compared to alkyd paints, oil paints and the rest. The qualities to consider are adhesion, flexibility and resistance to ageing. Serviceability may be a factor as well.

**thechemist** · 05-14-2003, 03:41 PM

Originally posted by Jorma Salomaa:
Thank you, Chemist.

It appears that the water permeation properties will vary from one latex to another, depending on a number of factors. If we consider permeability a crucial quality, how do we know which paint to choose? The paint manufacturer tells us nothing.

But how important is permeability? Is it good or bad that water travels in and out through the paint film? The ideal would be that water would be transported from the inside out but not the other way. We may not have that luxury. Much water out means much water in, which means more expansion and contraction of the wood which means more stress on the paint.

If we look for stable conditions we may have to look for a non-permeable paint film. If this is the case then we would accept latex only on the condition that its permeability is minimal. What do you think?

Then we have to consider also the other qualities of latex compared to alkyd paints, oil paints and the rest. The qualities to consider are adhesion, flexibility and resistance to ageing. Serviceability may be a factor as well.

I would think that the paint on the outside wants to be relatively impermeable and the paint on the inside wants to be relatively more permeable, either through molecular structure or thickness. This concept of different permeabilities of coatings has come up before, in the context of underwater coatings as I recall.

There is a certain ambient humidity of air, on the average, in some location. Wood may tend to an equilibrium moisture content with that ambient humidity level. When it rains, the ambient humidity is over a thousand times higher [liquid water versus vapor concentrations of water molecules]. If the wood is to have mechanical stability, then its moisture content ought not change quickly in response to short-term moisture variations, such as a day of rain. Longer-term, average atmospheric humidity will cause wood moisture-content variations, and the wood will move, thus the paint film must have some flexibility. If the wood expands seven percent from bone-dry to fiber-saturation point, the paint film must similarly have at least seven percent elongation, preferably double that as wood is an inhomogenous material and local stresses can easily exceed the average.

The bond strength of the coating to wood must exceed the force required to stretch the paint film by whatever elongation its service environment requires of it, otherwise the wood will separate from the coating. The tensile strength of the film must be greater than the tensile stress which wood expansion causes in the paint film by stretching it. The coating in any case must not develop in the wood more than 200 psi or so to stretch it, for that is about the shear strength of wood and the wood itself will fail at the coating-wood interface if the coating is too stiff [This is the liability of painting stiff epoxy coatings such as West on wood. One can get cracks in the epoxy coating] . All of that is basic enginering considerations, and useless in the real world as no latex paint manufacturer provides tensile modulus and related film properties' information. For that matter, I don't know of any enamel-paint manufacturers who do.

If you were using aerospace materials, you can get film properties and bond strength information, and between calculation and testing a decent coating system may be designed.

Latex paints are generally pretty stretchy unless flat. Paint some on a plastic bag, let it dry and peel off the film and decide for yourself. The issue for wood coatings will then be substrate and primer adhesion. Oil-base enamels and other coatings tend to have less elongation, but historically most are adequate. Again, substrate adhesion is important. You want to decide whether to paint a boat topsides with a latex? Have the latex supplier provide his primer and whatever guarantee may exist, that his coating system will stick to your wood.

I would expect latices to not hold their gloss as well as other types, since they do slowly go away [The self-polishing phenomenon is similar to that of hard vinyl antifouling paints, which do ablate albeit much more slowly that the soft, sloughing types.].

I would think a primary purpose of paint is to keep water out.

If adhesion is poor, or affected by water, then one can have blistering.

If gloss maintenance is not important, a latex may be adequate.

**Wild Wassa** · 05-14-2003, 04:10 PM

I've now grabbed a horse Oyster, hang on.

My bias against Latex is, apart from it's porosity, is that you can see it, you can actually see the film. I have a visual bias as well.

I'll try to describe it this way. If you go into a white wood wharehouse and look at a table, there is a painted table, if you go next door where the tables are double the price, you will see a table well coated, but if you buy a table from a craftsmen you see the wood and wonder whether the table is coated.

If your painting covers the wood, you will see the shape, form and colour, when I use latex, 'we' see the paint. The aim is, to not see the paint, not just brushstrokes.

That's the arrogance of being a painter, ... not just the horse's jockey.

Warren.

[ 05-14-2003, 05:49 PM: Message edited by: Wild Wassa ]

**On Vacation** · 05-14-2003, 06:57 PM

Where do you read anything about me pushing latex? This has been my whole point to this entire thread. Absolutely under no uncertain terms, Do I reccommend latex paint. Further more, if you will read my earlier post, you will find that I do recommend oil base primer on bare wood, Chemist.

Oyster
.
Member # 5154

posted 05-11-2003 09:18 PM
--------------------------------------------------------------------------------
. Woods sealed with oil has a better chance to survive in the long haul

--------------------------------------------------mherbert
.
Member # 4948

posted 05-11-2003 10:53 PM

As an example, my boat spent thirty years in Sitka, AK. The foredeck and cabin roof are canvas coated with Pliobond which is an industrial adhesive. Most people in the lower 48 say that they have never heard of such a thing. Well, it works. The wooden fishboats up there have been using it for years with no deleterious effects. Cheap, pliable, waterproof and effective. That tells me that acrylic latex might work well for cabin roofs, but not necessarily for the hull above the waterline.

My reply :
This line has an underlying factor involved in it, called canvas and properly sealed with an adhesive that probably was waterproof. If this is research further, you will probably find that the wood area and the wooden boats were cleaned regularly, sand, and painted, probably each year.

This cleans a lot of the mildew or mould spores up, and minimizes the rot issue. Also, I would think many fishing boats used salt water for more washdowns a larger marority of the times.

--------------------------------------------------
There are factors which you can get by with latex paint. Am I pushing it? Absolutely not. But part of this thread points toward the enviromentalist movement to do away with all of this "toxic paints"

by saying get used to it, it being 2007 we all must use latex paint.

You want to talk arrogance in making a living in part as a painter? Try telling someone that he or she must deal with painting a forty or fifty foot boat every year. That is not a stroy many wish to hear from someone they are paying to do a profesional job. They are expecting the job to last more than a year or two. But some people think they are being friendly to the enviroment and are saving money by using latex paints. Bull. Are people using it? Yes. Does it look good? Not to my eyes yesterday, today and never tommorrow.

The orignal discussion brought up water vapor, and blisters which hold water on as it would pertain to wooden boats.

You see, I am arrogant when it comes to painting. I am not interested in a job that looks like crap to a trained eye. But many only want it to shine when its done. There is a large difference in price to whitewash with latex and a job that last at least five years under normal operating conditions and average weather conditions.

We are seeing a different boat owner in the 2003 boating community.

[ 05-14-2003, 08:03 PM: Message edited by: Oyster ]

**JormaS** · 05-15-2003, 10:25 AM

Chemist, if we disregard the permeability factor, is it safe to say that a typical latex paint film has more longevity than a typical oil paint or alkyd paint film, thanks to its greater elongation and its inherently better ageing properties?

I´m trying to find the undisputable benefits of latex versus the rest, if any.

**thechemist** · 05-15-2003, 03:01 PM

Originally posted by Jorma Salomaa:
Chemist, if we disregard the permeability factor, is it safe to say that a typical latex paint film has more longevity than a typical oil paint or alkyd paint film, thanks to its greater elongation and its inherently better ageing properties?

<snip>

No, because it weathers away much faster than enamel paints chalk. Properly formulated 2-part polyurethanes can outlast them all, but you're looking at latex versus the others. I don't think acrylic latex has inherently better aging properties, compared to the inherent aging properties of oil-base enamels, including alkyd enamels. Naturally, any formulator working for a maximum-profit formulation will not produce as good a product as one formulating for performance alone, so product quality varies.

Paint some of the enamel paint you have available on a plastic bag, let it cure, peel off the film and see if it stretches a bit and can be folded double without cracking. Compare products that way, and you will be well on the way to being able to choose better products.

Originally posted by Jorma Salomaa:
<snip>I´m trying to find the undisputable benefits of latex versus the rest, if any.

It's water-cleanup. That's the only undisputable benefit.

**thechemist** · 05-15-2003, 03:38 PM

Originally posted by Oyster:
Where do you read anything about me pushing latex? This has been my whole point to this entire thread. Absolutely under no uncertain terms, Do I reccommend latex paint. Further more, if you will read my earlier post, you will find that I do recommend oil base primer on bare wood, Chemist.<snip>

Oyster, I wasn't implying you pushed latex. I was just discussing the general subject of latex paints and the underlying science, and airing my own opinions, which I freely admit are prejudiced in favor of other products in a marine environment.

**JormaS** · 05-15-2003, 04:45 PM

OK, so it seems that the majority has not been in favour of latex. At least for me it has been an interesting discussion. I think I have gained some understanding of this type of paint.

**Wild Wassa** · 05-15-2003, 06:12 PM

I have a confession, my rudder box is painted in acrylic, ... but not house paint. The real confession is it's paint from a tube. It was the colours that I was after. The paint is over epoxy and under clear w/b poly. Who would know it's latex.

Warren.

ps, I nearly forgot that I had done this, last year as a test.

[ 05-15-2003, 07:15 PM: Message edited by: Wild Wassa ]

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