Blisters! Is it Osmosis?

[Rakuflames]

Originally Posted by ShaunJ

Sara
I think you are on the right track as long as the blisters are small. One boat I looked at had very large blisters, 6 to 12" and I was told to run away and don't look back. I would assume large and numerous blisters are bad.

They're "bad" because they will slow the boat down and absorb water weight, but they won't sink the boat. They're also bad because to REALLY repair them, the boat will have to be on the hard about six months (so I'm told). I'm told that it takes that long to truly dry bad blisters out.

[psneeld]

You guys need to get with what's really going on. Water will soak into ALL resins including epoxy and start to deteriorate it. Epoxy is much more resistant... but it still hydrolyzes. Warm water accelerates the process. gel coat is actually the enemy.

This is going on whether or not blisters ever develop.

Most surveyors don't understand this any better than most of you.

STOP reading marine articles about blisters. LOOK UP/google/etc hydrolysis in many different manufacturing sectors and get the BIG picture.

I've posted picture of me ripping by hand off multiple layers of roving well into the laminate structure.

Don't believe me...fine...hope your boat doesn't end up like mine...but it very well could if you keep her in the water all year round in the tropics. You won't know for sure without coring the hull to sample the laminates or grind into it deep.

6 months on the hard won't dry out a saturated boat unless you take the gel coat off the boat (or at least off the wet areas (which yu don't know where they are without taking the gel off.

[osirissail]

Originally Posted by bugmon

. . . Are you telling me that polyester resin is porus ?

See: The Resin Families: Epoxies, Vinylesters and Polyesters
for a discussion of the various resins and water absorption.

Here is another good all-inclusive discussion of osmotic blisters and why: http://www.smithandcompany.org/GRP/GRP.html

However, everybody needs to specify what kind of blisters they are talking about. The two main categories are "Laminate Blisters" and "Gelcoat Blisters." The first is a serious problem and has structural degradation potentials. While the second is a cosmetic problem and not in anyway a structural problem.

Gelcoat blisters are very prevalent in "production" hulls and a real "eye sore." We have a "new" old boat in the yard and they had to gelcoat peal the entire hull from toe rail down and up to the other toe rail. There wasn't six inches of smooth gelcoat on the hull, it was all pocked with gelcoat blisters. It looked like a giant "Noni" fruit - uggg-ly.

[bugmon]

Originally Posted by mitiempo

Gelcoat, which is tinted resin basically, is porous. So is epoxy, although a lot less so.

A hull that is not cored can (and will) absorb water over time. But the weight increase will be small.

This makes absolutely no sense ( to me anyways) . For water to be absorbed Into something it therefore has to displace something. It needs to have room in whatever material it is being absorbed into.

What material in a hull is water being absorbed into?

I can understand if a void (air) is present then it could enter and displace that.
I can understand if a cored hull is compromised , then it could enter and soak that.
But in a solid glass hull what exactly is the water displacing to cause this osmosis?

[minaret]

Originally Posted by bugmon

"Some boats will saturate due to osmosis and never blister, just weigh a lot "

I dont get this, can someone please explain ... what material in the hull is saturating? Are you talking about a cored hull where the core is soaking water? ....or a poorly laidup hull that has voids and unbonded cloth?

Are you telling me that polyester resin is porus ?

That's exactly what I'm telling you- a polyester laminate is often porous. A modern vacuum-bagged laminate is obviously much less so, but any polyester laminate can become saturated if subjected to osmosis for long enough. Once saturation begins then hydrolysis also sets in and the whole ugly cycle begins. Hydrolysis is the process by which seawater converts solvents and other materials in the laminate into both a new acid and a new base. Hydrolysis effectively causes the laminate to become yet more porous over time, causing osmosis and saturation to become worse, which in turn causes more hydrolysis, etc. etc. Here's a good description of the process of ester hydrolysis-

Hydrolysis is a chemical process in which a water molecule is added to a substance resulting in the split of that substance into two parts. One fragment of the target molecule (or parent molecule) gains a hydrogen ion (H+) from the split water molecule. The other portion of the target molecule collects the hydroxyl group (OH−) of the split water molecule. In effect an acid and a base are formed.
The most common hydrolysis occurs when a salt of a weak acid or weak base (or both) is dissolved in water. Water spontaneously ionizes into hydroxyl anions and hydrogen cations. The salt, too, dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions. Sodium ions react very little with the hydroxyl ions whereas the acetate ions combine with hydrogen ions to produce acetic acid. In this case the net result is a relative excess of hydroxyl ions, causing a basic solution.
However, under normal conditions, only a few reactions between water and organic compounds occur. In general, strong acids or strong bases must be added to catalyse hydrolysis.
Acid–base-catalysed hydrolyses are very common; one example is the hydrolysis of amides or esters. Their hydrolysis occurs when the nucleophile (a nucleus-seeking agent, e.g., water or hydroxyl ion) attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water. In acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups.
Perhaps the oldest example of ester hydrolysis is the process called saponification (formation of soap). It is the hydrolysis of a triglyceride (fat) with an aqueous base such as sodium hydroxide (NaOH). During the process, glycerol is formed, and the fatty acids react with the base, converting them to salts. These salts are called soaps, commonly used in households.



The by product of acetic acid created by hydrolysis of salt water is one reason that water from a blister has that characteristic smell, leaching styrene trapped in the laminate being another. Of course the by-products of hydrolysis, like acetic acid and freed styrene monomer, are not things you want in your laminate either. This is also one of the many reasons drying a saturated hull can be so difficult-you are not just trying to remove water. You are trying to remove a chemical soup of water, acetic acid, various solvents, and hygroscopic salt. It's all very complicated.

[HappySeagull]

Tip: a wood carver's gouge and mallet are wonderful tools to work on a blistered hull with...

[HappySeagull]

noticed in Passing and curious of other observations... I've never seen blisters on fibreglass that has no gelcoat...say, where usage has worn it off ... but there are not many boats like that.

[LeaseOnLife]

Originally Posted by minaret

That's exactly what I'm telling you- a polyester laminate is often porous. A modern vacuum-bagged laminate is obviously much less so, but any polyester laminate can become saturated if subjected to osmosis for long enough. Once saturation begins then hydrolysis also sets in and the whole ugly cycle begins. Hydrolysis is the process by which seawater converts solvents and other materials in the laminate into both a new acid and a new base. Hydrolysis effectively causes the laminate to become yet more porous over time, causing osmosis and saturation to become worse, which in turn causes more hydrolysis, etc. etc. Here's a good description of the process of ester hydrolysis-

Hydrolysis is a chemical process in which a water molecule is added to a substance resulting in the split of that substance into two parts. One fragment of the target molecule (or parent molecule) gains a hydrogen ion (H+) from the split water molecule. The other portion of the target molecule collects the hydroxyl group (OH−) of the split water molecule. In effect an acid and a base are formed.
The most common hydrolysis occurs when a salt of a weak acid or weak base (or both) is dissolved in water. Water spontaneously ionizes into hydroxyl anions and hydrogen cations. The salt, too, dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions. Sodium ions react very little with the hydroxyl ions whereas the acetate ions combine with hydrogen ions to produce acetic acid. In this case the net result is a relative excess of hydroxyl ions, causing a basic solution.
However, under normal conditions, only a few reactions between water and organic compounds occur. In general, strong acids or strong bases must be added to catalyse hydrolysis.
Acid–base-catalysed hydrolyses are very common; one example is the hydrolysis of amides or esters. Their hydrolysis occurs when the nucleophile (a nucleus-seeking agent, e.g., water or hydroxyl ion) attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water. In acids, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups.
Perhaps the oldest example of ester hydrolysis is the process called saponification (formation of soap). It is the hydrolysis of a triglyceride (fat) with an aqueous base such as sodium hydroxide (NaOH). During the process, glycerol is formed, and the fatty acids react with the base, converting them to salts. These salts are called soaps, commonly used in households.



The by product of acetic acid created by hydrolysis of salt water is one reason that water from a blister has that characteristic smell, leaching styrene trapped in the laminate being another. Of course the by-products of hydrolysis, like acetic acid and freed styrene monomer, are not things you want in your laminate either. This is also one of the many reasons drying a saturated hull can be so difficult-you are not just trying to remove water. You are trying to remove a chemical soup of water, acetic acid, various solvents, and hygroscopic salt. It's all very complicated.

Damn, back to school....

When you mention salts, one question comes to mind, are freshwater boats prone to more or less blisters?

Thanks!

Dirk

[minaret]

Originally Posted by LeaseOnLife

Damn, back to school....

When you mention salts, one question comes to mind, are freshwater boats prone to more or less blisters?

Thanks!

Dirk

Fresh water boats are definitely less prone to blistering, and ester hydrolysis is one reason why. Hydrolysis can occur in fresh water but it is much more likely and also accelerated in salt. Production orthotropic resins are more susceptible than isotropic resins or vinylester, external mix chopper gun laminates are more susceptible due to more solvent retention and less than perfect mixing of catalyst, etc. etc. There are a thousand factors that can potentially come into play, such as accelerants like MDA or Cobalt, the variation of resin recipes from manufacterer to manufacterer and over time, and so on. The quick answer without getting into all this is to make sure your boat is barrier coated unless it was built in epoxy or vinylester, and even then if you want to sleep well at night.

[bugmon]

Originally Posted by HappySeagull

noticed in Passing and curious of other observations... I've never seen blisters on fibreglass that has no gelcoat...say, where usage has worn it off ... but there are not many boats like that.

I've owned Lobsterboats all my life and the last four were fiberglass . Every year we wear deep grooves into the hull with the rope we use for our groundines and there are gouges past the gelcoat into the woven where the traps hit the hull. In the spring we haulout and paint over everything with bottom paint and off we go. I've Never had a blister of any kind in any of my boats in the 25 years I've been fishing with glass boats.
In the times that I've had a bad ding I've glassed some mat over the hole and painted alittle gelcoat over it and its fixed.

Barrier coat?? lol I dont think so...it wouldn't last a month

[minaret]

Originally Posted by bugmon

I've owned Lobsterboats all my life and the last four were fiberglass . Every year we wear deep grooves into the hull with the rope we use for our groundines and there are gouges past the gelcoat into the woven where the traps hit the hull. In the spring we haulout and paint over everything with bottom paint and off we go. I've Never had a blister of any kind in any of my boats in the 25 years I've been fishing with glass boats.
In the times that I've had a bad ding I've glassed some mat over the hole and painted alittle gelcoat over it and its fixed.

Barrier coat?? lol I dont think so...it wouldn't last a month

This logic has always tickled me. MY boat doesn't have blisters, so how could anyone elses?! Believe me, it is a common phenomenon. And if you have been reading the thread you will also have noted that a lack of blisters does not mean a lack of osmosis, saturation, or even hydrolysis.

[mitiempo]

Originally Posted by bugmon

This makes absolutely no sense ( to me anyways) . For water to be absorbed Into something it therefore has to displace something. It needs to have room in whatever material it is being absorbed into.

What material in a hull is water being absorbed into?

I can understand if a void (air) is present then it could enter and displace that.
I can understand if a cored hull is compromised , then it could enter and soak that.
But in a solid glass hull what exactly is the water displacing to cause this osmosis?

Solid is not the best way to describe fiberglass, regardless of which resin is used. Appearance of solidity might be better. But the holes are really, really small.

Once the moisture penetrates the gelcoat it is in the layer of mat which is composed of short pieces of fiberglass that are held together with binders. These binders are supposed to dissolve in the styrene in polyester resin - there is no styrene in epoxy. Nothing is perfect and some binders do not dissolve depending on the care during layup and the mix of the resin. Some resin doesn't cure properly. The water finds its way in and they can travel down any strand of glass that is not totally encapsulated quite easily. The water molecules mix and undissolved binders and uncured resin, expanding to create the blisters. Rarely does the moisture go farther than the layer of mat closest to the gelcoat. It is cosmetic not structural. This is the blistering that is the most common. It has spawned an entire industry.

Sometimes due to bad building practices, bad resin mixes, or Uniflite's famous fire retardant additive the moisture works its way into the laminate inside of the gelcoat. This is structural, Uniflite and the Valiant hulls they built (after a forced fire retardant additive change) being the most widespread and publicized in a production run to my knowledge. Structural damage past the first layer of mat is rare.

[bugmon]

I'm not saying that there aren't people with blister-related problems .... but after reading this thread I'm beginning to think that certain people are over-hyping the topic.
Here is a good read Sea Lake Yacht Sales (Kemah, TX)

I subscribe to that line of thinking more than most that I've read here

[mitiempo]

I have read that article and tend to agree with it as well. I have linked to it elsewhere myself. Jan de Groot is a respected surveyor with decades of experience. As I posted above gelcoat blisters are the most common and are not structural - only unsightly. But as I also posted they have created an entire industry of gelcoat peeling etc. Many spend thousands to repair blisters only to have them return years later.

[psneeld]

The problem with thinking blisters and not hydrolysis is that huge potions of many boats are possibly starting to delam (like mine) when the blisters don't seem too bad and the surveryor didn't catch it.

Then the unsuspecting new owner of a boat pops a few blisters, fixes them, slaps on some more bottom paint and heads for the islands where the warm water all year long is dissolving more and more resin and the delam is getting worse and worse.

Here's some laminate that much of it I could pull off by hand due to it's almost dry of resin yet didn't show up as delam yet to a tapping hammer..