West System barrier coat failure and what we learned

A Barrier Coat Application Resulting in Blisters

When the new barrier coat treatment failed and resulted in blisters all over the hull for both us and our boat neighbours, that had used the same treatment from West System, we spent hours upon hours trying to figure out what had gone wrong. After talking to the manufacturer, and other boat owners for 6 weeks, there was no option but to remove both epoxy treatment and Coppercoat and start all over. Neither the manufacturer nor anyone else could ever provide a clear conclusion to why this had happened to two boats in the same marina. But from everyone we talked to we have been able to make some conclusions about epoxy in general. We have decided to sum it all up here in hopes that this will not happen to you next! If we could turn back time but keep the knowledge we have now, we would never have chosen the West System epoxy barrier coat for our project.
What happened?
In the summer of 2020 we decided to redo the epoxy barrier coat as we were changing from traditional anti-fouling to Coppercoat. We did this with the West System barrier coat, sharing a can of epoxy with our boat neighbours that were doing the same treatment. One of the reasons we chose this epoxy treatment was because of the very detailed manual that is provided with the epoxy. We also talked to Coppercoat representatives to confirm that this epoxy is compatible with their product, and it is!  We finished our summer projects in September, and relaunched Linnea just as everyone else was preparing to haul out. Our boat neighbours had by that time concluded that there was something wrong with their treatment as they found blistering on the hull. We spent 8 months in the water and hauled out again in May 2021, only to find that our hull also was also full of blisters.  So now we were two different boats, that had shared the same can of epoxy, done the treatment in different conditions (like time out of the water, hull manufacturer, time of the year, people doing the treatment and so on), but that had got the exact same result. Based on this, it was not hard for us to jump to the assumption that there had been something wrong with the epoxy or instructions we used. This is why we decided to contact the manufacturer in hopes that they would help us with a cause and solution that would not mean spending a second summer up on the hard redoing all the work we had done the summer before.
Different theories
First Assumptions
To everyone we talked to, their first assumption was that the hull had been damp in the core when we did the treatment, which it was not. When doing new moisture readings, it wasn’t even damp, after spending 8 months in the water. We have also had a lot of people thinking it was osmosis in the hull, because that is pretty much what it looked like. But these blisters were between the gelcoat and the epoxy, with no damage to the hull or gelcoat whatsoever. 
From the Manufacturer
From the manufacturer, who was sent samples of both the blisters and the liquid they contained, they concluded that there had been some kind of contamination. They had a lot of theories as to where this contamination could have come from, none of which we believe provided a sufficient explanation to such extensive blistering in two boats. This, we spent several hours trying to discuss with them, but unfortunately never felt like we got any ear for.  What is even more astonishing when it comes to the manufacturer, is that we talked to a fellow boat owner that had the exact same thing happening to his boat 10 years prior. He had received the same answers as we got even though the manufacturer had “never heard of such an issue before” when we talked to them. When he, on his own, had investigated this further, he found information that these solvent-free epoxies (like the West System) were known (in the “epoxy business”) to be really sensitive to the environment in which they are applied. Meaning that they are only reliable if applied indoors in a completely controlled environment. As we painted the rudder indoors, this could explain why it was completely blister free. However, there is no word in the epoxy manual that this is something that you should take precaution against. 
Some Conclusions in General 
So this is what we wish we had known before starting this project and what we learnt while preparing to do our second treatment. 
  • Solvent free epoxies are known to be really good if applied in an environment where you can control all the environmental factors that can affect the curing; like temperature, moisture/dew, solar radiation, and wind. In other environments, like for us who painted outdoors, they should not be trusted to provide a reliable result, especially if doing such a large treatment as an entire barrier coat treatment.
  • Solvent based epoxies are much less sensitive to the surrounding environment as it cures much quicker. 
  • When a solvent free epoxy is used on top of a solvent based epoxy (like when applying Coppercoat), it is important that the solvent is allowed time to evaporate from the epoxy. Otherwise, the solvent could try to escape afterwards, resulting in blisters. 
  • Solvent based epoxies can also cause blistering if it comes into contact with bare GRP in the hull. For this reason, any deep scratches or dents in the outer gelcoat must be repaired with a solvent free epoxy before any treatment can be performed with a solvent based epoxy. 
  • Solvent free epoxies may not provide a very good adhesion to gelcoat. 
  • Acetone could cause remaining solvents to escape from the epoxy. This is why, for instance, Coppercoat is very clear in their instructions not to use acetone to clean the hull before application. 
  • Whichever epoxy you are applying, talk to the manufacturer before, even if it looks like they provide a very detailed manual. Ask about specific weather, temperatures, conditions of your boat, preparations, cleaning, and so on. If you run into a problem, reach out again. And try to get as much as possible in writing! 
  • Document everything you are doing. Write down batch numbers, moisture recordings, temperatures, and dates. Take photos of as much of the process as possible. 
Our Thoughts

In the end, we had to redo it all, all at our own expense, and with our own time. West System offered to provide a new batch of epoxy for the new treatment with the understanding that we were to refrain from ever mentioning the issue in any social media ever again, all as a gesture of “goodwill” from their end. As we don’t feel comfortable using their product again without knowing for sure what had gone wrong, and as we believe this is important knowledge to spread in the boating community, this was an offer we very strongly declined. In their opinion we are to suit ourselves for ending up in this situation and therefore they had no intention of providing any economical compensation for the issue or us taking 6 weeks of trouble trying to cooperate and accommodate them with filling out forms, sending samples and talking to their representatives. 

For the second application we chose a solvent based epoxy, discussing the project with the epoxy manufacturer several times (it actually says specifically in their manual to do so), and also receiving additional information from Coppercoat on what to do differently this time. We keep our fingers crossed that this knowledge now has provided a good result that will last for many years to come. 

We hope you have found this interesting and might help you in any upcoming project. Please leave a comment below if you have some additional thoughts or questions, and help us spread the word to help any other fellow boaters not to end up in the same situation 🙂 

25 Responses

  1. Väldigt spännande. Jag är Möbelsnickare och jobvat mycket med båtar mest trä. Använt epoxi i många år.
    Blev väldigt nyfiken på hur mycket info ni sänt till west. Var det bara till svenska generalagenten elker gick ni vidare.

    Tänker på att det var någon form av kontaminering. Men vad är det som epoxyn inte gillade som gjorde dessa blåsor.
    Hur djupt dök ni ned i olika lösningar. Tänker på olika sandpappers bindemedel som gör att pappret inte sätter igen.
    Skulle väldigt gärna av ren nyfikenhet och vill alltid lära mig mera. Höra av från er.

    mvh pär

    1. Tack 🙂
      Vi sände all info vi hade om båda båtarna till West och deras tillverkare Gougeon Brothers, Inc. Vi gick till och med så långt att vi hade telefonsamtal med högsta VDn i USA, men den mesta av kontakten fördes med deras tech-team i UK. De hade även en representant från Danmark som var över och tog egna prover och studerade hur det såg ut.

      Det svåra med teorin om kontaminering är att man skulle lyckas hitta något som lyckats kontaminera båda båtarna. De pratade mycket om att det skulle varit kontaminering i acetonen vi använde (men vi använde ju inte samma aceton på båda båtarna), eller att det skulle suttit något på skrovet som vi svepte runt med acetonen. Även sandpapper och vilka trasor vi använt diskuterades (men även här hade vi använt olika). För vår del så känns det som att det antingen var en kontaminering som kom från epoxin eller något med klimatet som gjorde det. Teorin med klimatet är att eftersom det tar ungefär 2 dagar innan det är genomhärdat så måste förutsättningarna vara samma under hela den perioden, vilket det så klart inte var eftersom vi var ute. Vår köl klarade sig ifrån blåsor, men den är i massivt bly och har ju ett trögare klimat än skrovet, och rodret som målades inomhus blev också bra.

      Tyvärr fick vi aldrig mer svar än så. Vi försökte få till en lösning att West skulle komma hit och ta upp båten på land (inomhus) under hösten för att hjälpa oss göra om det och ha möjlighet att ta ännu fler prover men det var tyvärr inget de var intresserade av och tillslut kände vi att det enda vi gjorde var att hjälpa dem förstå sin produkt bättre utan att få någon hjälp tillbaka så då avslutade vi dialogen och började skrapa bort allting på egen hand.

      Hoppas det gav dig lite svar på dina funderingar 🙂

  2. The blister you show above appears to be between the old gelcoat and the barrier coat. This is not what I had expected from reading the text ….. between the barrier coat and Coppercoat.

    Using acetone to wipe down before any coating is not good …. as it will leave oily residues that get into the new coating.

    It is my understanding that solvent based epoxies are more porous because of the small holes left as the solvent escapes.

    If I ws applying Coppercoat I would not apply any other fresh epoxies beneath due to the possibility of contamination. For instance West Epoxy leaves amine on the surface ….. and it takes a while to fully cure.

    1. Yes, it is correct that the blisters appeared between the gelcoat and barrier coat… And to use pure acetone (without oily/emollient additives) is very common here, it is even one of the recommended cleaning alternatives in the West System manual.

      Solvent based epoxies are, as you say, more porous and in theory solvent free epoxies result in a more compact barrier. But even so, solvent based epoxies, if applied to the correct thickness, will provide a moisture barrier that is more than sufficient.

      Applying epoxy under Coppercoat is very debatable, and we did it because we believe that as you buff and/or sand the Coppercoat surface you will over the years remove some of the barrier the Coppercoat has created, making it thinner and thinner. We talked about this with Coppercoat, and they have very specific procedures to handle the different epoxies underneath to create a good bond and dealing with the amines/escaping solvents. The Coppercoat had boneded very well to the West System, and it did bond just as well to the GelShield we applied this year, so I have no doubt they know what they are doing 🙂

    2. West Systems only recommends Acetone to decontaminate the area you are about to sand in prep for the barrier coat. They tell you to wash it with water after the sanding phase to get rid of any remaining residue. Acetone also puts gellcoat and non-105 epoxies into a state of “acceptance” as in it disolves the surface slightly. If you allow Acetone to dissolve the surface and then rub more in you’ve contaminated the entire area mate. Its crucial that of you are using large amounts of Acetone that you remove the residue with water even if you are using the two cloth method to catch any contamination as the Acetone is in its latter liquid stage pre evaporation. Again, I build boats for a living and used thousands of litres of epoxy over the years and what I’m telling you I you contaminated your gellcoat provably with Acetone as the decaying gellcoat areas soak in Acetone and other cleaners like a microfiber cloth and they need watered down with a hose for hours sometimes till the last of it comes out. We litmus test to ensure its done. You’ve clear as day made several mistakes in your application. Read instructions and data sheets carefully mate you use Acetone to decontamimate and area you are about to sand, then use water or 99% iso then water to do the final wipe down. You can also use a waterbased degreaser like spray painters use but make sure its the actual proper stuff that garages use and not some ebay bottle of it.

    1. Va tråkigt att höra att ni råkat ut för samma! Använde ni också West? Vi fick tips om att göra om epoxibehandlingen eftersom den var sen 2004 och vi inte hade någon historik angående vad den råkat ut för sen dess (tex skador eller liknande som inte åtgärdats korrekt) och vi skulle göra lite förstärkningar och därmed bryta skyddet av den gamla behandlingen. Det, i kombination med att vi skulle lägga just Coppercoat som ska vara i 10+ år, gjorde att vi valde att göra om det så att vi skulle kunna vara säkra på att vi har ett fullgott skydd i många år framöver.

  3. We asked Coppetcoat whether we needed a epoxy coat after the hull was stripped back to the gel coat. The reply was “No, Coppercoat is an epoxy- no need for an extra layer”. So we didn’t. No trouble at all. We applied our own Coppercoat outdoors while in Trinidad.

    1. That is true and something we also discussed. However, we choose to go with the theory that as you buff and/or sand the Coppercoat surface you will over the years remove some of the barrier the Coppercoat has created, making it thinner and thinner, so we reasoned that it would be good to have a protection underneath that would not be affected in the same way. Different theories, but all supported by Coppercoat 🙂

    2. Coppercoat is not a proper epoxy mate, very little are. People call poly and vinyl resins Epoxy these days so that’s why they’ve claimed that. It would however still work fine if the gellcoat was prepped properly so you’ve obviously done a good job.

  4. Hi! Ni dök upp på min instagram och sen såg jag att ni hade lite bekymmer med west system,
    Jag har gjort hela min swan 59 ink fairing
    Med west system och var lite nyfiken på proceduren som ni genomförde innan ni la på produkten, tvättades båten, vilket slip papper som användes och dem olika stegen, mer detaljerat då jag inte såg nån info på de,

    Alltid intresserades av chatting,
    Vi tänkte dra jorden runt så småningom, häls Rusty

    1. Hej!
      Proceduren har gåtts igenom av West System och dess tillverkare i alla detaljer och man har inte kunnat hitta något som både vi och våra båtgrannar gjort likadant eller använt samma saker, därför har vi inte beskrivit detta mer i detalj här då det helt enkelt känns irrelevant för vår historia. Skicka gärna ett mejl om det är någon specifik detalj du vill veta mer om! Tyvärr kommer vi inte ha möjlighet att beskriva hela proceduren på nytt då vi försöker lägga hela den här händelsen bakom oss, hoppas du förstår!

  5. Thank you for your research and sharing outcomes! I will change my plans based on your excellent decision to share the truth!

    1. I’m so happy to hear that you found our information useful and that it will help you not end up in the same situation! Thanks for letting us know and good luck with the upcoming project!

    1. Oh no! I’m so sorry to hear this!
      It looks like you, just like us, did the job outdoors? Sounds like another “proof” that the West System barrier coat procedure does not work in those conditions… Hope you will find a solution 🙂 All that money down the drain really sucks! Our use with GelSheild seems to be working a lot better this far 🙂

  6. It is money, but also a month of hard work during our holiday. Our 5 years old child helped us as much as she could all that time. We were all so happy finishing this. We just couldn’t belive this “bad joke” when we have removed the tape to see how it looks like.

    Did you buy the Coppercoat for the second round? Or also some other product?

    1. Yes, I totally agree about the months of hard work! It was terrible! And definitely felt like a very bad joke..

      We bought a new round of Coppercoat for the second time, yes. In our opinion the Coppercoat had worked really well, and that was the product we wanted to use as antifouling. So that’s why we went with that again!

      1. This is wrong. All wrong and I’m suprised West Systems had the patience for this. OK my credentials are- 4 decade boat builder involved in every part of marine including marine mech. I’ve built over 200 boats and used every material there is including carbon fiber on racing boats, even tying carbon fiber into GRP and I mainly oversee the final stages now from the fairing through to final polish.

        OK, I don’t know who in the trade would be daft enough to tell you what you just claimed about ‘outside/uncontrollable application area’ as West Systems is the best in bad conditions bar two other specific resins that I won’t name here as its not about them, however, they are specifically blended mostly on the catalyst side to be applied in wet humid conditions and they Aren’t anywhere near as strong or watertight as West Sysyems is once cured. I only use them when the repair area might meet a wash over from a wave or two within maybe 30mins of applying. Right so your claim West Systems is an indoor Epoxy is factually wrong as its one of the very best and easiest to use outdoors. Further proof of this is that we are In Scotland and do outdoor fixes down to -5deg In absolutely treacherous rain and wind. If you are in any doubt throw peel ply over it and problem solved. EVERY actual boat builder on earth worth their salt will agree with me on everything I’ve just covered on this and it’s not up for dispute, West Systems 105 and the correct hardener for the timeframe is unbeatable indoors and one of the best outdoors.
        Moving along,
        I read everything you said and even from the relatively low amount of info you have put on here regarding how you done your mixture (how you stirred it, what size batch you mixed at once etc and what type rollers and brushes etc) that you have havent prepped the area correctly then its became contaminated because of that. This is common and the exact results of not removing bad areas and bad gelcoat back far enough. We’ve seen this countless times with DIYers and they end up bringing it to us to fix it as they cannot fathom why it never worked for them. The first thing they do is blame the Materials and yet its nothing to do with who’s Resin it was, it was the application that was wrong. I can tell from the blistering that it’s a bad prep job and the critical part is when you mentioned that the epoxy had blistered off the gelcoat. Yeah that’s called contamination buddy as the matrix that properly applied West System uses for a bond would NOT delaminate in such a way, on yours it’s lifted off from contaminated spots likely because your cleaning agent soaked into the bad gelcoat spots that you never prepped correctly. The reason the bad gellcoat stays on and delamination happens above it is that the gellcoat is bound to the material so is effectively “gassing out” all its decay to the surface area and because it holds more moisture in it when you layer over it with anything then you are painting directly onto a contamination patch that will gas out hars as soon as you trap it in and you will have a adhesion failure spot within 24hr. Again, this is common and usually folk find this out the hard way on paint jobs rather than the barrier coat stage especially with West Systems as its so forgiving.
        There is no more to discuss about it as I can physically see its contamination and since I’ve used over 5000 ton of epoxy in my lifetime I’d say you should take it as gospel. I’ve built entire boats from West Systems outside on our yards In way way worse a climate than you are In and not had any issues bar maybe the odd time ice gets a hold of it and it needs a heater placed in what exists of the boat at that point. I hope you realise that you’ve made a mistake and contaminated your project by either bad prep or bad application. It’s nothing to do with the resin.. and the info you gave out on what works the best in which environment is completely wrong, infact it’s the polar opposite from the reality.
        I dont wish to insult anyone but to mess up with West Systems hahaha Yeah just get a pro to do your boat mate, you’re not cut out for doing boats mate you had the best resin for the job and still messed up.

        1. Hi David,
          You seem very passionate about epoxy. Thank you for taking all this time to comment your thoughts on our process and result.

          Please note that our website and posts is not directed to professional, but rather happy boat enthusiasts and DIYers like ourselves.

          From your comments you seem more confident in the failure of our process and capabilities than the professional West System representative that was sent to deduct test and take samples from the boat. Please note that West System and Gougeon Brothers had us provide them with every detail possible in our work, they had representatives sent to us in the yard and could still not conduct any final conclusions on to why this had happened to two boats in the same yard. We have spent hours making contact with different people both who are more knowledgable than us, but also people whom have had the same issues, and what it boils down to is the conclusions we have stated in this post. If West System and Gougeon Brothers had managed to make any conclusions applicable to both boats I’m sure they would have let us know. Like you, they also first believed it to be contamination but could not find a common contaminator applicable on both boats. I think the only ones you are insulting is actually West System and Gougeon Brothers, insinuating that you would know better then them in this matter. But yeah – good to know your opinion in our capabilities, it will sure affect our coming boat work 😉

  7. Hi! First of all, shout out to you for talking about just how essential it is to fix the outside gelcoat with a non-solvent epoxy for any significant dents or scratches to keep it waterproof. I feel like the right thing I should do now is telling my cousin about this so he can take appropriate preventative actions pronto. He just bought a water slide for his backyard pool recently but noticed some minor damages on its surface.

    1. DIYers give out terrible advice and don’t realise what they are saying. You should be removing all the bad gellcoat, barrier coats are effectively a Tie-coat, they are only to be used over areas where there might be a maximum of about 3mm of surface area that isn’t prepped or cannot be prepped (like pin holes and crevices from paint removal and the likes) It’s NOT a magical wonder potion that fixes large unprepared areas or larger spots of bad gellcoat or whatever, That doesn’t exist. If you have bad gelcoat areas then it needs to come off. It will soak every bit of cleaning agent or thinner, degreaser or whatever you put on it into it and effectively need a pressure hose pointed at it for about an hour to rince the contamination out of it. You can physically see and feel when gell coat is holding in contamination as it feels oily fkr a few secs ever time you soak it.
      The critical part here is if you are doing a DIY job and you aren’t a boat builder then you are better just putting In the extra days and weeks of prep and going back to the bare material and going from there with a well known resin and final finish combination that are known to work with each other. Most paints are fine with West Systems as long as you get rid of the amine blush and at the very minimum read the data sheet on which grits to use between coats. Again, people think its OK to go a bit lighter on grit or a bit heavier on grit than what is called for in the data sheet but its not OK at all. You are compromising the bond there is no excuse for it and the difference between even 80grit happy primer and 240grit happy primer can mean all the differnce as the stuff designed for 240-600grit surfaces will turn gummy and never dry correctly if you spray it into 80grit prepped surfaces. The HB or 80grit happy stuff will turn out like plastic paint if you apply it on anything north of 240 grit surface prep. Now the reason I’m saying about the paint is just to show how easily it is to mess up with the wrong type prep that you spend days refining it to the wrong grade.. I’m not even meaning a NO-prep scenario… which is obviously the worst thing you could do. Its like people who try to rattle can job their car then start moaning because it never works right for them… thats because it’s hard to spray paint full stop and you need to stick to the Tech Data Sheet its an absolute must. Remove your bad gellcoat people

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