2.1. No longer actual.
2.2. No longer actual.
2.3. No longer actual.

2.4. Woven roving creates more triggers.
2.5. Some blisters are harmless and only cosmetic.

2.4. Woven roving creates more triggers.

The use of roving in one of the 3 - 4 outer layers often results in more trigger type styrene enclosures being formed.

2.4.1. Styrene surplus is divided by the roving meshes.

The styrene emitted from the curing gel coat is divided by the roving meshes.  Instead of a few "normal" enclosures it forms a lot of smaller enclosures between the roving and the next laid layer and / or in the roving meshes.

2.4.2. "Fish net action" causes penetration of enclosures.

When the next layer of mat is laid or sprayed over the woven roving mat, fibre ends are apt to protrude into the meshes like fish into a net.
Thus more styrene enclosures may be penetrated from such fibreglass ends.

2.4.3. Roving provides a "highway".

The multitude of long straight fibre strands in the roving bundle are seldom totally wetted from the polyester resin.

They provide capillaries for the hydrolysis process which, compared to chopped strands, are like an empty highway for a car instead of passing through a medevial town!

2.4.4. More space for molecules delays gel coat blisters.

Even if the process proceeds faster, capillaries along the roving strands can accomodate many more molecules than along chopped strands.

Therefore the hydrolysis proceeds invisibly during long periods and causes severe deep damages before gel coat blisters form.

2.4.5. The woven mat bond is severely disintegrated.

Even in a sound laminate the bonding of the woven roving to the next layer is somewhat disturbed by the styrene enclosures.

As the hydrolysis proceeds unnoticed for such a long time in the woven mat, the mat will separate from the underlying laminate in certain areas.
This separation provides additional space especially for the big salt and glycol molecules. Often there is enough space for salt and glycol also to absorb lots of sea water.

If the hydrolyse in the roving is allowed to proceed unrepaired for a long time after gel coat blisters become visible, the separations of the woven mat will be noticeable as big soft spots in the hull.

2.5. Some blisters are harmless and only cosmetic.

Mainly the styrene enclosures emitting from the curing of the gel coat are formed between the first two laminate layers or deeper. Under certain conditions they may form between the gel coat and the first layer.
Then the polyester will remain uncured only between styrene and laminate but not between the styrene and the gel coat.

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In water temperature over 20ºC, styrene molecules will pass out through the gel coat blister into the sea. Water will enter, first by diffusion and then by true osmosis.

When the ideal proportions of styrene and water have formed, the break down of the uncured polyester will start. In this case the reaction is not retained by insufficient space and the gel coat will blister immediately.
Acid and alkali will react normally (just as by boiling tests see 4.3.1) and form glycol and neutral salts. As the alkalis are weak and the acids strong, the salts will cause some acidity when dissolved in water.

Without any surplus acids the "osmosis" process will stop when all of the uncured polyester is broken down. It will not spread within the laminate, but the blister may grow to the size of a thumbnail or more due to water entering by true osmosis.

2.5.1. Harmless "osmosis" blisters are less acid.

Typically the blisters form within a few years and only in some areas of the hull.  The contents of glycol and salts dissolved in water are very fluid and will eject in meter long squirts if a blister is ruptured.
The acidity is low and the smell is somewhat "rotten" instead of acrid.

2.5.2. Harmless blisters may exist together with the fatal.

Often both types of blisters show on a hull. It is therefore important to check blisters in different parts of the hull before deciding on treatment.