Epoxy Coating GRP Hull and Bilges

This flyies in the face of all the peer and independant testing, so I guess you can believe the world is as old as the bible says it is or carbon dating data, your call.

This isn't the appropriate approach to seal and waterproof wood with epoxy and no formulator or experienced applicator will tell you to do this. It's tough to compare apples to oranges.

I know of and partly listed, the usual and various formulations of clear coatings on wood. I didn't list them all, but the fact I listed them separately suggests you've made another incorrect assumption. Each of these formulations has an effective range of preventing moisture vapor ingress (the real key to waterproofing), none especially good compared to other products.

You are correct in that quality materials and most importantly the ultimate care these coating receive are the real issues and in this we're in complete agreement.

The bottom line is how much moisture gets past the coating, assuming it's well cared for and kept in good order. I don't know of anyone that will spend thousands of dollars per gallon for the $35 an ounce stuff you suggest, especially if you have to recoat every year like we do in the tropics. I would like a recommendation from you as to the better, reasonably affordable varnishes and clear coatings for wood and other porous substrates.

It's likely we have more in common on this fairly complex subject then not, but it scope can get pretty "thick" pretty quick and this likely isn't the best venue. Try out the Alumithene, you'll be surprised about it's abilities. I've given it the "dog test" which is a test 5 gallon bucket in my backyard, where I dump test samples. The bucket fills and evaporates with rain and the dogs prefer to drink out of it, rather than the nice clean stuff I supply for them. They also like to take sample pieces for a little run occasionally and I have to go around the yard, find them and place them back in the bucket. This testing bucket is literally hell on whatever gets the call to live there for 6 months or so. Canine incisors dents are very similar to bashing into an oyster bed, for example and I'll bet dog spit isn't very far off what you'd find in a tidewater.

You are obviously much more informed than the usual poster, but my usual recommendation is for the use of a non-reactive, viscosity modifier with your epoxy, plus the hot on hot method to get a very thin, yet still 100% solids epoxy into a substrate. This guarantees good bond attributes and good strength, both exponentially better then a CPES treatment. Lastly, yes epoxy is permeable, but so is the polyester hull you're applying that CPES to, but is the moisture ingress so low that it effectively becomes waterproof. Polyester alone needs help, epoxy doesn't. Again try the balsa test, you'll quickly see how ineffective it is.

 

I personally know of at least one dinghy with a 1958 original 2 pack varnish finish still on it. No it has nor been kept in a museum but used a lot including Championships to the mid 90's. Not sure it will make 300 years but how many carriages that age still get used every weekend? and in a salt water environment?

Again my experience would support PAR and his thinking. I'm not averse to good quality polyester builds at all, but on older ones that need re-sealing, epoxy is your best friend. Right now I am repairing an old Otter which even has clenched copper rovings (or had) holding some of the timber in place. Do I think that clenched rovings and silicon broze ring shank nails along with an 'older' glue are superior to modern(ish) epoxies with suitable fillers? - No. Strange to find a fibreglass boat with Roman or older technology as a primary fasterner, still I figured out how it was put together and saved a few mm on the chisel end!.

 

...and I was trying to escape the complex discussion.....little time at this point...research on the necessary things to finish the boat fast..work on the boat....historical research on red color, cochineal and trade that I need to deliver....a violin maker's forum that I used to post but have no time anymore..regarding varnish, history and sound (audio engineer/record producer in past landlubber life).. and time to drink wine or beer with the wife.....so I tried to find a fast way out..another forum...no time.... ..so much stuff to do.....but, your points are good and I'm no chemist...so I need to think this with a fresh memory and try to explain best what I see/feel happening to the materials...tomorrow morning I hope I can make some sense of it...if I am lucky I will find some sample picts..

Interior or exterior?

If interior, does it get a lot of uv?
Does it get a lot of water as in bathroom/kitchen?
Is it a high abrasion area (where people hold themselves to all the time, or a table) or is it trims and walls?

Each one of these a different system.

all the best...

 

Cool, by 2 pack you mean two parts? What is it? (I'm curious) Is it transparent or did it become that yellow opaque stuff that looks as it does not belong in the wood as most modern material varnishes become? the old style basically died in around 1935, but some of the older style stuff could still be found in 1958??

interesting..

 

Well, we boatheads will want exterior, marine grade (hefty soaking probable), with as much UV resistance as practical. If possible and a nice feature if it could self apply after opening the can - one I'd willing pay $35 an ounce for too.

My apologies for maybe some of the stiffness in previous posts. You see, we often get these types of questions and stead fast adherence to marketing hype, without an understanding of the physics and chemistry involved. You're obviously one with considerably more understanding, maybe not at the molecular level or the pure physics of it, but certainly from a practical view, abet from a different perspective (that sounds interesting as hell too).

 

Ok, I'll try, see if I can communicate well enough....

Epoxy coating of polyester, epoxy coating of wood, and varnishing got all mixed up in the chat as if it was one thing...my fault....since I was using a varnish method to communicate an idea about penetration, solvent and effect it has on wood... so let's take one at a time...

On Polyester....it is clear that it is porous, and a epoxy barrier coat helps, now a thick epoxy will only travel so far, a thin one will travel further, it is thinner, simple, at this point don't think about water protection only about penetration, I have done lots of tests with different solvents, thinning thick epoxy, and I ended up with something similar as it is describe here, every time.

http://www.epoxyproducts.com/penetrating4u.html

Now I was skeptical of CPES, because of my tests, but my friend who is one of the most knowledgeable persons on finishes I have ever met (he helped to develop several major products out there, no relation to Smith's company), insisted it was a different animal, and it is, the stuff is vicious, it penetrates like no other epoxy based product I've seen can, it wicks in and stays there, so the polyester being porous, an this being thin, it get in deeper. I am using it as a adhesion promoter in the first place, you can easily see when you apply it, it does not sit on top as the other epoxies, but it goes in, an infusion epoxy goes in deeper than a west systems type, but not as deep as this thin stuff, don't need to believe me, try it.

Once that is in there, before it fully cures, I apply a thicker epoxy which will adhere and bond to the CPES that is in there, and not to the polyester,that way I get much better adhesion, and the other advantages I've mentioned before.

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Now to wood impregnation with epoxy.... I have read the West Systems claims that their stuff goes in as deep, and other manufacturers too, and it may be true in some scenarios, but not on most. Just take a piece of red oak for example, place the end grain in a tray with CPES, and another in another tray with regular epoxy resin, the CPES will travel through capillary action fast and much further than the regular epoxy...

Now if the CPES's molecule once dry has a void because of the solvent evaporation or not it does not matter, because a thicker epoxy will come later. I have done lots of impregnation with normal epoxy on wood, and have seen many failures, usually because it has been hit with something sharp, it is brittle, it cracks and the wood is exposed. Now CPES goes in deeper, and it is not as brittle, and if hit the outer layer will chip, not the CPES, so wood continues to be protected, now it differs from the other because of reasons I can not explain. But will try anyway.

When a tree dies, it goes trough several processes, and looses it's massive amount of liquids, and resin, which helps to halt the decomposition process, organic peroxides are formed and the resin begins to crystalize..chain reactions happen and oxidation and polymerization...and all that stuff you probably know better than I...

So now we have this dry wood, and depending on what I apply, it gets happy or it gets sad, if you add sugar, it gets happy, as it has lost it's sugar, if you put Nitric acid it gets sad....

Now I can not explain in chemical terms, but that is the main difference, you appy CPES, and you get happy wood, the resins are made out of the stuff in the tree and not petroleum, maybe that has something to do with it.

Now it needs more thickness for the water protection, and I am not savvy to the chemistry but perhaps something with more solids for better water protection, now, I have don the test, and Illstreet infusion epoxy after CPES will go in deeper than the West stuff, and it makes the outer structure of the wood much tougher because it is much harder, I had two other experienced boat workers check it out, and see if I was not trippin', and they agreed, it was obvious.

Plus there is an old saying in the varnish world, and I forgot how it goes, but it is something like this..

Two coats will not crack, three coats may crack, four coats will surely crack..

But if you do dissimilar layers, than it becomes a lot more forgiving, specially if following the fat over lean rule.

Also if it is tighter "in" the grain, instead of "on" the grain, you get more depth of film, without brittleness, better adhesion and it aids in the non cracking of the film when moved in manners the epoxies don't like.

Than the West epoxy goes to finish necessary film thickness, but now Wests film is not as thick as if it was by itself, so it all becomes stronger. More work to apply, a little more, but worth it.

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And to varnish:

Exterior and floor varnishes are the ones I have the least experience with. My last boat had none of both. But I did apply it outside before I sold her, and did some thinking and research.

My new boat has it, I am stripping the toe rails this week. It has one of these normal varnishes, that I don't like, for several reasons.

I don't believe a varnish should ever be removed, only retouched, but these varnishes made of most alkyd or phenolic resins with UV inhibitors such as the Basf Tinuvin and others have to be, because they become ugly. You take one of these varnishes, make a puddle and leave it on the sun for a couple of years on top of aluminum foil and you end up with an opaque ugly yellow thing, it is the way these resins and UV work.

Than there is the cracking, they are applied thick and crack in an ugly manner, it is just a matter of time or getting hit the right way.

An the refractive index of these varnishes don't match so well with the wood's and they are not "in the wood" but "on the wood", and when you look at a shiny perfectly applied modern marine varnish you get a reflection on the top layer, that is wrong, the reflection should happen in the wood, not in the varnish, it makes is so that you don't see the wood, you see plastic. As I am removing this stuff from my toe rail, a beautiful wood is appearing, the varnish has not increased DOI (Distinction of Image), it has not increased contrast and it has not imparted great visual depth.

So what is the solution?

I don't know, but I have two different theories, one that I tried for a brief moment and then sold the boat (a 65 foot 65 ton trawler is too big for wife and I), so I don't know how log it lasts, and the other one which is what will go on my toe rails now.

One thing I know, I hate to to touch ups and take care of exterior varnish.

First theory:

If the proper wood has been used, such as Ipe or Teak, no sealing or protection is necessary, so it is for looks only.

Now some of these woods have an oil called Lapachol, which will slowly push the varnish out of the wood, so a varnish that penetrates in the wood and gets sucked in is an option.

Look at this picture of the penetration of a purified linseed into the wood (Allback in this case)

http://www.solventfreepaint.com/i/linseedoil-penetration.jpg

but the oil does not offer a strong enough barrier for water and bacteria that will develop, also dirt. So the right resin in the highest amount possible without becoming a film that will crack and be pushed out by the Lapachol is an option. Just make sure to fom time to time, come in with a cloth and wipe a new coat...

But before applying the finish I treated the wood with Borax, so it will delay bacteria, as long as the borax is still there.

That is one option, recipes for this, is another discussion.

 

Now the other theory. The right resin to use is the East India, I don't believe it is available anymore (I can not find it), my friend who is a master varnishmaker bought the last 30 pounds from the East India company had while closing their doors, but perhaps something similar can be done with semi fossil copal?

The trick with the East India is that it can handle more UV and Salt water than any other resin, barnacles hate it too, it used to be used in ships bottoms.

Now we use a system similar to the violin system, or to what has been done in some coaches to preserve gold or expensive pigmented details from the action of weather.

The initial coat is dilute and has a high resin content, soaks in as much as possible, give it as much as the wood will take in the first app, the high resin content will offer more protection from moisture, and will be protected by the following coat of the same varnish but in a long oil cook.

This way the Lapachol should not push it out, because it is deep into the wood's structure, and the film can be a little thicker without cracking.

Similar principle to violins and to my CPES impregnation above. I believe these violin varnishes have survived 300 years only because of this system, it is 300 years of handling, playing, sweating, bruising.

Now same as violins, I will keep the film only as thick as it needs to be, no more, no grain filling. No need to grain fill to look expensive, as the materials are special.

Now where to buy stuff like that, I don't know, perhaps the closest may be the violin varnishes made of Amber or Copal such as these. But it is made for a different use, so I am not sure, and they are little bottles not large boat amounts, I could never afford these varnishes for large jobs, for a table it's different.

http://www.violinvarnish.com/varnishes.htm

A similar thing can be done with epoxy first and a modern oil based varnish after, high resin - long oil system, but both will become ugly in 10 years max, and the epoxy will be hell to remove... I hate removing varnish, so this is a bad system in my book.

A good varnish made with the right ingredients and prepared the right way will become better and better looking, pentimento begins to happen and increases transparency.

The other trick is instead of UV, use pigment. not the cheap monochromatic poor looking stuff, (some synthetics can be complex colors, but difficult) but the natural complex looking, it does not cost much more for us, it does cost much more for a large company though.

Kremer is a great source.

http://kremerpigments.com

Still need to research if it is better more of a translucent pigment, or less of an opaque one...

The thing to keep in mind, for exterior use, you don't want to use a color that will look bad in places where the varnish has worn of, so use a color that enhances the wood color, not changes it. My teak has a light golden color, so I may use this stuff for the first layer, and something darker for the second.

http://shop.kremerpigments.com/en/pigments/raw-sienna-badia--italian-40404:.html

The translucent iron oxides my be interesting for this.

http://shop.kremerpigments.com/en/s...ry&desc=on&sdesc=on&keywords=translucent iron

The varnish becomes tougher (as in cement) and the pigment offer a much better protection than the UV stuff, and it has no shelf life.

Make sure not to add too much and loose transparency, and mull it in well, than some more, this is a great muller at a decent price.

http://shop.kremerpigments.com/en/t...uller-with-handle--large-1-piece-883350:.html

Some of the pearlescent pigments work great too (in small amount) now these can not be muller because they are mica coated.

http://shop.kremerpigments.com/en/p...ibri-iriodin-star-gold--very-fine-50111:.html

http://shop.kremerpigments.com/en/pigments/pearl-luster-colorstream-magic-indian-summer-50651:.html

http://shop.kremerpigments.com/en/p.../pearl-luster-mira-magic-sun-gold-50016:.html

http://shop.kremerpigments.com/en/pigments/pearl-luster-pyrisma-yellow-50061:.html

I hope this helps a little

 

I have yet to see a 300 year old violin that looks the same as it did when it came out of the luthiers!. For starters it has most likely been rebuilt 10 times and tweaked. The fingerboard would definitely have been changed as worn out unless never played. I count nuts and bridges as expendable replacements btw.
Just how crystal clear were they? All the timber has discoloured from it's fresh state because of UV whether European Spruce and sycamore or whatever. It is just wood so it will either darken or lighten and mostly yellow even without any finish.

Perhaps surprisingly I have gone into these finishes a little because I also build acoustic guitars. They do have a carbon fibre epoxy bowlbacks, you may not consider them to be 'instruments' but I can assure you they are professional quality for sound (looks too) and record very well too. I deliberately use a soft finish on the top or table as it is often called to get more vibration or rocking couple which is the primary driver of sound.

This is not what you need on a boat. A boat requires a more stable finish that enhances the stiffness of the structure, long life, water sealing and UV resistance. Shellac aka French Polish is a long way from meeting these requirements likewiase hide glues for remaining waterproof when immersed. Some of the current offerings of finishing systems are extremely good when applied correctly.

Maybe it is just me, but with the greatest of respect and I genuinely do respect your knowledge of instrument and other finishes what is so terrible about the best marine systems available today? I believe copper bottoms were obligatory on vessels after terredo worm ate through the timber unless a lanolin and vegetable oil mix was applied. But these are oils not varnishes.
There are other oils that are pretty good at water repelling too and the type of timber counts as well ie Douglas Fir decks and larch that can last over 100 years continous use. Can you clarify the whether you require an oil ie saturating and remains soft or a true varnish that sets in its own right? I count shellac as an oil btw, funny how it water stains....

 

You don't have to have "thick epoxy". Many formulators (not West) are mixing viscosity reduction into their offerings. West System's only advantage at this point is for the novice, that hasn't a clue about the various offerings and the specialty user, where their specialty coating systems can be employed. Very few professionals use the 100 and 200 series resin/hardener products from West, as these are the old school formulations and not at all reflective of what modern formulations provide.

If penetration is desired, this can be accomplished with technique and you still get 100% solids as an end result, with is the most desirable. When you look at the modulus, peel and other physical properties of CPES and your intent is to use it as a bond promoter, sealer or tie coat, you have to ask, why, simply because of the grotesque difference between a 100% solids product's physical properties and CPES. Especially when you can get the same substrate penetration with technique and possibly non-reactive modifiers too. Simply put, you can get 10 times the compressive strength, 5 times the tension strength, 3 - 4 times the peel strength and a waterproof membrane, with the same penetration, plus it bonds to the substrate much better too and makes a fine primer or base for a primer or sealer for clear coating.

The bottom line with wood is two fold, stabilization and waterproofing. This assumes you'll handle UV in some other fashion. No product I've seen yet, with the exception of a 100% epoxy will stabilize wood's moisture content. CPES can't and frankly is only as good as a quality varnish in this vain though does have a much higher peel strength. A stable joint or structure doesn't move, doesn't test it's glue lines or joints, fasteners don't egg out their holes and themselves can be entombed in goo, preventing them from corrosion too. This is why epoxy has taken over in the land based construction industries, as far as fastener bedding. Mild steel machine bolts and lags don't rust when placed in the once typical "anchor shield". The current practice is to "bond" the fastener in epoxy, skipping the shield and the buried piece of fastener will never see air or moisture again. The second issue with wood is water proofing. This can get pretty technical, but as simply put as practical, if you start with relatively low moisture content, use established encapsulation techniques, the piece if immersed will pick up some moisture, but it's threshold is low enough to remain below the range where mold, rot and other damage can thrive. This is why most formulators insist on 12 or less moisture content, because they know an immersed piece might pickup a few percent, making the piece's content go up to 15%, but still below the magic invisible line, commonly recognized at about 17% moisture content, where rot and other beasties can get a grip.

Back to using a weak bond to saturate a substrate, then bonding over this with a much stronger bond. In a nutshell, this is akin to painting over dirt. You've applied a weak, yet deeply penetrated sealer and now will bond to this with something much stronger in every regard. The logical route is a much better bonding sealer, possible not quite as deep, but really a few thousands of an inch isn't going to hurt anything. Lets say you bashed your CPES sealed, epoxy over coated whatever into something and this damage has penetrated 1/2 way through the initial CPES penetration level, but is below the 100% solids penetration. What's going to happen? Well, you'll have damaged wood, below the waterproofed over coat and you'll get moisture gain. What happens if you've bashed into something with a strictly 100% solids epoxy coating that been breached below it's penetration line? The same thing, moisture gain, so how has The CPES treatment helped?

As I mentioned, all the tests (which initially surprised the hell out of us) have repeatedly prove is it's not the amount of penetration that counts, so much as the quality of the coating. By quality, the physical properties thing rises up and to boat builders, mostly water proof, just isn't close enough, in light of the absolutely waterproof examples that have decades of "in service" testimony to provide. You can have a deeply penetrated goo, that's not waterproof or very strong or a very strong, water proof goo that's perpetrated just as deeply of nearly so. Which do you think a builder wants.

All this said, there are uses for penetrating epoxies, though I don't buy them, preferring to make them up as needed. A good example is to harden the edges of carvel planking, so it can be recaulked, yet still allow moisture into to swell the planking closed. Personally, I think this is a ham fisted way of doing things, but some folks are looking for just a little more time, before they have to replank the bottom and this can get them a season or two more. Another example is a frame replacement I recently did. The frames in this boat where so bad, disassembly would have caused the boat to collapse. I used penetrating epoxy on the frames and planking, to stabilize them enough to permit their removal, without destroying them in the process.

 

I don't think anyone knows what they looked like back then. But this may be the closest? (as far as in know, and i know very little I believe it has never been retouched). The lesson to learn from the violins is that the ground (first layer of varnish close to the wood) is tough and survived on most of them, and it looks prettier than any other varnish out there.

I believe that if the right wood is used, Ipe or teak for example, no protection is necessary, it is only a issue of looks.

I never mentioned Shellac as an exterior finish.

What is terrible about the marine finishes? Read what I wrote, it is terrible, for me, I am not a contractor who delivers a job for an client and than have no idea what is happening on the boat's daily life 5 years down the road, I am the user, these are the issues I have, and I search for a better solution, for myself, I don't mind sharing, but I don't need to prove anything either as if it goes bad I am the one to repair it, for the interior I've found something I am happy with and that is not a modern varnish, since I became a varnish maker I have no use for modern varnishes, now I don't advise anyone to do that is it is dangerous, for exterior, still experimenting.

The new varnish that will go on the toe rail, I can not take credit for, it is made and thought by a master varnish maker friend of mine, who has made me one Vernis Martin, that is stronger, more beautiful and easier to apply than anything modern I have ever seen, by a long shot, but he is a true artist of the craft, a genius on his field, I will never get there.

 

What are the products used by the professionals instead of the 100+200?

What technique is this? Heat? (if so it is not enough)

Do you have any data to back this up?

 

I use a proprietary extra slow mix, from a local formulator. The West System 105/200 series formulations are actually pretty basic and about the highest markup product available. This said West System does have much better specialty formulations for different application processes, such as post cure and infusion. Most professionals employ more refined formulations either from West or other suppliers and the number can be extensive. As a rule the 105/200 series is for those that don't know the formulations and are relatively new to epoxy use. We consider it the "retail" version, for folks that shop at West Marine for their boating needs.

There are a few techniques you can employ to lower viscosity, plus formulations that are dramatically "thinner" right out of the container. The hot on hot method is well documented and gets the goo as deep as necessary. Simply heating the resin isn't very effective, but but heating both the resin and substrate is very effective. Again, it's not the depth of penetration that's the goal for us, it's waterproofing and moisture content stabilization. Some penetration can be handy, as you previously mentioned, in the event of a coating breach, that gets below the level of penetration. In reality, damage occurs, often well below any coating depth (including CPES), so you have to address these accordingly.

Of course, I'm not known to be glib about my comments. I generally just call it the way I've seen it, usually from a practical view. This type of data gets into the area of black boxes, magic, trade secrets, etc. Most don't like to release this type of information, but with some digging and testing, you can find enough to make reasonable assumptions. I performed a series of tests, now several years ago, concerning the usual penetrating formulations and their resulting physical properties. West and other have also done this. Elongation modulus will drop dramatically with just a 10% cut, similar changes will also occur to tensile, compressive and other attributes. How dramatic these changes are of course depends on the formulation, but a 50% drop in tensile modulus with a +15% cut, isn't unusual. CPES is a 37% cut, so you can draw reasonable conclusions just from this, but again, do the balsa block test I mentioned previously. Better yet, just pour an 1/8" thick layer of CPES into the bottom of a cup and let it cure for a month. Do the same with some 105/200 and conduct some rudimentary tests. The real butt kicker for me is the peel test, which is what happens inside the cellular structure, within the wood it's penetrated. If it has a lousy grip here, everything that's on top of it also has the same lousy, moisture vapor permeable grip, which for a boat builder, isn't a big draw.

In your applications, stabilization and waterproofing likely aren't as big a concern as they are with us.

 

Other epoxy systems worth looking at include SP Systems and the Araldite family, amongst many others. The latter is considered good enough for aircraft manufacture with composites, although some of them can be used with timber too. Try a bit of research, and you will find working times up to several hours but other things like cure temperatures, moisture conditions etc etc. Also hardener colours, transparent ones are available for medical use amongst other things so that it is safe to touch internal body parts in an operation. Warning, only approved epoxies should be used for this as they have been tested.

However epoxy is still one of the best resins around that combines the properties required, structural strength (and cohesive bonds), waterproofing and toughness. In pure toughness terms, polyurethane is better than steel. An example would be coin sorting machines which use polyurethane belts and funnels as well as chutes because 1.2mm steel only lasts months not many years service.

On the other side of things, most musical instrument makers use soft finishes especially on the top of their instruments ie guitars, cellos, violins etc because it is advantageous to have maximum movement as it is part of the sound generation. In fact many would say no finish at all would be best but real world use dictates some sort of moderately cleanable surface. French polish is pretty common, although I'm not sure it takes beer spilt on it well!

 

Iteresting Par, some of the pro's I know here where I am use the West 100+200's stuff, so do some major yards, but there are so many products in the US, and since I have not been here for a while it's a lot to learn, and don't want to risk it, so have been using the stuff the pro's here tell me to use - 100+200 but would like to learn about the better ones, which I am sure are out there.

On Penetration, I understand your view, and the Illstreet infusion epoxy (slow cure) goes in quite deep, and it may just be enough, but it seems the CPES goes in deeper through capillary action. It appears it becomes more part of the wood.

From what I understand your tests where performed with another dilute epoxy at 15%, I have done that too, similar conclusions to yours, but the CPES is a different animal, it behaves differently, and solvent is not necessarily a bad thing, not all solvents are the same just as not all turpentines are the same, and the behaviour of tree vc petroleum resins are very different, even different petroleum resins have different properties, such as Syrian Asphalt compared to Gilsonite. I am doing some tests with CPES at the moment. I have done adhesion tests on my CPES+Illstreet+West 209 system and adhesion is great on plywood.

Suki, thanks I will look into these products. Yes Polyurethanes are great resins, and the high solids are the best exterior paint, just don't like it on wood, too much work to refinish.

I am not a maker, but most makers say that when the instrument is varnished it tames down some bad characteristics of the instrument, the oil varnishes IMHO being much superior for instruments than the spirit or shellac, speaking of looks, I love shellac for it's adhesion, even in oily or greasy substrates, and it pushes the oil or grease out of the film, and for it's UV's properties, it loves UV. A properly prepared Button Lac filtered with diatomaceous earth will get you down to about .2% wax, granulated activated charcoal will give you a virtually wax-free shellac, dissolve it with anhydrous alcohol etc it can handle water much more than the normal shellacs.

For an instrument Joe Robson's varnish is the best I've seen, it will last longer and look better than shellac, and it sounds great, for the last guitar I had commissioned I insisted in his balsam ground and the Amber Varnish (super tough, water and beer proof), colored with the dark rose and purple alizarine (super concentrate and last forever), don't know anything better yet, it has great depth, contrast and dichromatic/dichroic properties. It may seem expensive but not if you count the amount of hours put into an instrument (usually 2 months or more) Plus a very well varnished instrument sells.

Thanks again for the answers.

 

If a pro is using the 105 system from West, they really don't know what they're working with and more importantly the offerings/advantages/disadvantages from West System's product line. This isn't a professional, so much as someone at the yard, telling them to run down to West Marine and pick up another $120 gallon of goo. I'm paying $70 a gallon for a custom formulation and about $40 for a regular formulation. A real pro knows the products he employs and usually gets the considerably better price point, that comes along with some research into the subject too.

Yep all coatings have things to consider, like the ability to repair polyurethanes for example. The single stage two pack polyurethanes dominate the higher end of our market, for their durability, though on wood, elongation can be troublesome, unless epoxy encapsulation is used.

I've been working with single stage, two pack acrylics lately and enjoy the ease and cleanup, plus the colors are seemingly much brighter out o the gun. I know a few using the two pack two stage acrylics, having similar results as my single stage, with more durability and better UV resistance too. For the stuff I do, the 2 stage, 2 pack systems aren't cost effective, but I see them becoming an all in one system soon. Currently, you can get real 2 pack, single and double stage paints in spray cans. They use twin pressurized canisters, inside the can and the two parts mix at the sprayer tip (my assumption). Epoxy paint is now being sold like this two, so I do see a day when you can by a gallon size can, with a 2:1 - 3:1 mixture contained within and you just plug in a disposable tube and spray head.