4.1. Misleading articles and laboratory reports.
4.2. More contaminants in "osmosis" laminates.
4.3. Glycol believed to be "the big villain of the problem".
4.4. Dibutyl phthalate in the laminate causes "osmosis"?
4.5. Delaminating "osmosis pressure".
4.6. Hygroscopic materials cause delaminations.
4.7. Summary of common false believes.

4.1. Misleading articles and laboratory reports.

Besides misleading articles mentioned there are lots of other reasons for the confusion.

Before the HYAB research there existed very few laboratory test reports of actual "osmosis" affected hulls other than of small brick drilled samples

Only a few reports about the contents in the gel coat blisters can be found, some being analyses while others are theoretical. Formulas several lines long, often different and contradictory are presented.

This can be understood by a chemist but is very confusing for people involved with common boat production or boatyard labour.

In fact not only does the blister content differ in each hull, but they continuously change because of the instability of the chemicals involved.

4.2. More contaminants in "osmosis" laminates.

Many analyses of actual "osmosis" laminates reveal a much higher content of WSM:s, glycol and free styrene than normal for sound laminates.

Instead of understanding that most of the contaminants are created by the hydrolyse, the laboratories involved state, that "osmosis" is a consequence of too much contamination of the original laminate!

4.3. Glycol believed to be "the big villain of the problem".

Minimal amounts of glycol residues can sometimes be found in sound FRP laminates. One of the oldest theories about "osmosis" claims, that the process starts when water is attracted by this glycol. This is supposed to explain why only some FRP hulls are affected.

To prove the theory, laboratory reports from resin manufacturers are presented.

4.3.1. The tests refer to boiling of unaffected laminate.

Such tests are all of the type, where samples of FRP unaffected by "osmosis" are boiled in distilled water, which is the fastest way to make water effect a polyester glass laminate.

The boiling causes the styrene enclosures to expand and to rupture the covering "balloons" of not hardened polyester.

4.3.2. Hot polyester is plastic and permeable.

As with all plastic materials the polyester softens at a certain temperature. For polyester used in boat manufacturing this temperature is about 80ºC.

At boiling temperature the cured polyester is soft enough to provide practically free passage and space for the molecules formed, when the mixture of water and styrene breaks down the uncured polyester.

4.3.3. Alkalis can not escape like they do in an actual hull.

At boiling temperature all the acid molecules react with the alkali ones. The reaction forms only neutral products, mainly propylene glycol, glycol esters and salts.

Due to the heat this process is very fast and completely different from the "osmosis" reaction in a FRP hull.

4.3.4. No aggressive acids remain after a boiling test.

As the acids that create the esters are strong and the alkalis mild, the salts formed will turn slightly acid when dissolved in water.

There will be no surplus phthalic acid like in an "osmosis case, only small amounts of acetic acid from the binding agent, which is also dissolved by the boiling and the entering water.

Even If the boiling proceeds for hours, the properly cured polyester is not seriously harmed. Also all reports mention that the breakdown stops when the boiling is finished.

4.3.5. Blisters formed by boiling have a different content .

The molecules formed by the boiling also need more space and are forced out of the FRP. They cause blisters in the gel coat similar to the "osmosis" ones but with totally different contents.

The hot gel coat is very plastic. Most of the surplus, like the styrene, is gaseous and escapes easily. Only fluids, like glycol, diluted salts and a small amount of acetic acid, remain in the blisters.

4.3.6. No "osmosis" starts if samples are left in cold water.

If the boiled test samples are left in cold water for long periods, nothing happens except that the blister content is diluted by water. No de-laminating forces or typical "osmosis" damages occur.

This confirms the HYAB conclusion, that no "osmosis" can start without the presence of uncured polyester, styrene and / or free phthalic acid.

4.3.7. Styrene free laminate is "osmosis" resistant.

The water resistance of cured polyester became very evident at the HYAB 7-hour boiling test of repaired "osmosis" damaged laminates (see 5.2).

Samples repaired in a way, that they still contained styrene and acid residues were severely affected. Samples where all styrene and acid had been removed were not affected at all.

4.3.8. Boiling tests have no relevance to "osmosis".

Checking the difference in weight before and after boiling is a very adequate test for determining the water resistant qualities of different polyester laminates, but it has no relevance whatsoever to the "osmosis" process.

4.3.9. Boiling tests are easy to misinterpret.

The boiling test reaction proceeds exactly as expected theoretically and the boiling procedure also creates blisters containing glycol.

It is natural for a reader having "osmosis" in mind to misinterpret the reports, especially as some of them also provide theories (but no tests) why boat hull blisters instead contain acids:

Theory 1: Some of the alkalis vanish into the water before reacting with the acids, causing an acid surplus.

Also the HYAB team believed in this theory before our laboratory tests proved it to be wrong.

Theory 2: The acidic reaction is caused by acetic acid which is confirmed by the typical smell.

This must evidently be wrong as we have found the worst and most acid "osmosis" among old hulls where methyl acetate bound damp mats have been used. Further all analyses of the blister fluid, despite the different formulas, show phthalic acid to be the basic ingredient.

It is true, that the strong acrid smell found in the blisters is caused by small amounts of acetic acid from the PVA binder.

4.3.10. Descriptions of resin production add to confusion.

Another cause for believing in the "glycol" theory is, that most literature about polyester manufacturing does not mention anything about alkalis and the de-hydrolyse of water molecules. Only the mixing of semi-manufactured propylene glycol with phthalic acid and maleic anhydride is mentioned.

It is then easy to believe, that if too much glycol is added, this may result in excess glycol enclosures in the laminate.

4.3.11. The temperature difference hull contra sample.

It seems strange, that no report mentions the different conditions between a boat hull in cold water and the test samples in boiling or hot water.

One explanation may be that most of the tests are related to the manufacturing of architectural FRP panels, where the sun would provide the heat needed to keep the process going and rain and humid air the moisture needed.

4.3.12. Misinterpretations of boil-test reports.

"Osmosis experts" attempting to explain "osmosis" often base their theories on boiling test reports. In spite of being both confusing and contradicting, their theories are forwarded to and believed by yards and boat owners.

Books written only a few years ago by established "osmosis" surveyors claim that "osmosis" starts in glycol enclosures in the FRP and are often used as a reference.

4.4. Dibutyl phthalate in the laminate causes "osmosis"?

Some reports mention that small amounts of dibutyl phthalate are formed as the resin cures. Trapped in the laminate it is dissolved by intruding water into phthalic acid and butyl alcohol, ingredients commonly found in gel coat blisters. Dibutyl phthalate is therefore claimed to be the cause of "osmosis".

In reality the amount of dibutyl phthalate in a hull would not create phthalic acid enough to fill more than a couple of the hundreds of blisters found on a hull.

4.5. Delaminating "osmosis pressure".

In spite of being the most incredible, the osmosis pressure theory is the most widely spread among yards, boat owners and journalists.

4.5.1. Long squirts of osmosis fluid prove high pressure.

Some publications mention that "osmosis pressures of 20.000 psi and more" are created in the laminate and cause de-laminations. This is claimed to be proved by the long squirts of fluid emitted from punctured blisters.

The actual pressures are actually more in the range of 2 psi. The pressure in a toy rubber balloon filled with water is similar to the pressure involved. If the balloon is punctured with a needle, the water will squirt quite a few meters!

Probably the term molecular pressure has been misunderstood and interpreted as osmotic pressure (See 4.6)

4.5.2. The term "osmosis pressure" is misunderstood.

Osmotic pressure, is the pressure needed on the most concentrated side to prevent molecules of pure solvent from penetrating a semi permeable membrane. separating two solutions of varying concentrations.

Note the word semi permeable which means, that only molecules of the solvent can pass through it.

4.5.3. Gel coat is an absorbing substrate, not a membrane.

As earlier mentioned the gel coat is an absorbing substrate which can absorb moisture. Sea water together with most of the substances dissolved in it can pass through.   In or out depending on the surroundings

4.5.4. No true osmosis is involved in the blistering.

Instead the difference in concentration of soluble materials in the moisture inside the laminate and the sea water will even out by sea water entering through the gelcoat and the same amount of the higer concentrated solution migrating out into the sea.

This will neither cause any pressure nor any blistering!

4.6. Hygroscopic materials cause delaminations.

Almost all popular "osmosis" literature claims that hygroscopic materials, preferably glycols, attract water and create high pressures.

Such high pressures are only involved on the molecular level when water molecules enter the molecular space between the molecules of the cured polyester.

If the molecular space is totally filled with water molecules, the molecular gravity in the polyester is disturbed and the material contracts with high force (up to 20.000 psi) and speed.

The water molecules are too entrapped to escape, and the pressure brings them together into small water droplets which in turn cause circular cracks in the contracting polyester where they then remain ( so-called "disk cracking").

This has nothing to do with the start of "osmosis" and further the cured polyester in a hull seldom becomes saturated to such an extent.

4.6.1. Hygroscopics only absorb what is space for.

Squeeze a sponge in your hand and submerge it in water. Did it force your fingers to open???

Or presume that your car engine is filled with a highly concentrated glycol solution and that the expansion tank is refilled with pure water. Does the engine break in pieces?

4.7. Summary of common false believes:

4.7.1. Glycols cannot cause or speed up "osmosis".

The insignificant glycol impurities that exist in not post cured FRP laminates, play no part in the "osmosis" process.
Just like the trapped styrene they are covered with a balloon of uncured polyester which water molecules are unable to penetrate.

Even if water for any reason were to mix with the glycol, neither "osmosis" or any kind of pressure could be the result.

4.7.2. So called W.S.M:s cannot start "osmosis".

Small oobalic napthenate and dibutyl phthalate impurities may be dissolved by the water but cannot start the "osmosis" process.

The butyl alcohol can speed up the inward penetration of aggressive "osmosis" residues.

4.7.3. Dissolved PVA binder only provides the smell.

The PVA binder is dissolved by intruding water, but the acetic acid produced has nothing to do with the "osmosis" other than providing the smell.

4.7.4. Osmotic or hygroscopic forces cause no de-laminations.

At no point of the "osmosis" process are pressures formed high enough to cause de-laminations. Rumours about the high pressures originate from reports about "disc cracking".

4.7.5. Sea water in de-laminations kills osmosis theory.

During the HYAB OsmoCure test period 1993 - 1997, hundreds of fluid filled de-laminations were found and repaired on hulls earlier treated by common dry and shield methods.

The fluid in the de-laminations has in every case consisted of acid and glycol diluted by large quantities of salt sea water. With osmotic forces involved, only fresh water should have entered.

This proves both that there is no osmosis and that the epoxy water-shield is not sufficient to stop the water from being absorbed by the laminate!