Hi TheLandLady!
Yes, still kicking…just not as high
Osmotic (chicken pox) blisters are variable dependent upon how the boat was made, the conditions of when it was made, the way the boat is used, how long it sits in the water and how it is stored when out of the water. There are lots opinions of speculations and a few factual articles about what and why osmotic blistering occurs.
First a little bit of simplified ‘how it was done’ processing….
The manufacture site was coastal Southern California a region known for susceptible to large temperature, humidity and climactic changes.
The hull female mold is sprayed with mold release.. generally a silicone.
The gelcoat is spray applied to the mold interior.
Then a polyvinylester resin is sprayed over the gelcoat.
Glass cloth is applied and rolled.
More polyvinylester resin is applied either manually or by spray.
More fiberglass cloth is layered and rolled.
(Repeat until desired thickness of structure is reached)
Then typically a layer of resin incorporating a wax is applied to seal the exposed surface and the assembly is allowed to cure.
The production was done in non-environmentally controlled open shop areas generally with the doors open for ventilation.
Now if there are cold days, humid days with gaps in the processing time it makes it more or less apt to entrain moisture which leads to porosity of the structure.
In designing composite structures for things like aircraft and jet engines ( yes jet engines use quite a lot of composite materials particularly in the fan section casings, fan blades and stators) one of the most critical aspects are the conditions under which the composite parts are assembled. Environmental conditions are critical and must be controlled for the materials to react, cure, and work properly.
An open shop floor subject to uncontrolled humidity (Low? High? Foggy?), temperature (Hot? Cold? Alternating?) and other environmental factors like the amount of time an in process hull coat/layup is allowed to rest between sequence steps ( A few hours? Overnight?, Over the weekend? Over a holiday weekend? Longer?) all come into play when making a composite structure like fiberglass resin structures are susceptible to moisture migration into the laminate.
If say the mold is prepared first thing on a cold winter morning with lots of fog or a low dew point with high humidity that’s gonna trap a fair amount of moisture into the gelcoat making it more likely to be porous due to the entrained moisture.
Take that susceptible porous hull and now age it over a decade or two.
Maybe in a cold climate, maybe in warm climate.
Maybe just wet it for a day or soak it for months.
Maybe in fresh water or salt water or brackish water or all of them on a variable basis.
Maybe haul out a long term slipped boat in late August or wait until the lake nearly freezes and winter sets in with freezing temps.
Maybe add in damp cold humid and snowy weather alternating with hard freezing cycles where the structure never really get to dry out.
This can result in the inward migrating moisture being trapped within the porous fiberglass repeatedly expanding & contracting.
Add in some bacteria with the migrating moisture to generate some trapped acidic guck to eat at the pocket surfaces and inbetween the material layering. Kinda get a bit complex trying to give a simple uniform answer of which particular hull will be afflicted and to what extent the affliction will present itself. Hence why some hulls get blisters and some don’t. Why some have mild cases and some have worse cases. Why some …
You get the picture.
Sooooo…. Once blisters appear the owner has a choice of how to deal with it or not which is solely their choice and circumstances.
There are a couple ways to mitigate the blister problem depending on the owner’s preferences and resources.
The clean, prep, sand, fill, epoxy barrier coating, ablative bottom paint method.
—- This generally removes the damage and cures the problem…
The give it a good long dry out in a hot dry climate, clean, prep, epoxy barrier coating, ablative bottom paint and hope this stops it from recurring or at least minimizes the problem going forward method
The dry out, clean, prep, epoxy barrier coating and hope this is good enough given the owner’s usage patterns and minimized the problem going forward method.
The pretty much leave it alone as the usage is intermittent and there is lots of time between usages to dry out method
And the ignore the issue entirely, leave the boat in the water with minimal use and only deal with it if it really becomes something that can’t be ignored any longer (although I have seen cases where the entire thickness of a fiberglass hull has degenerated into a spongy porous rotten mess which oozed water to the interior bilge…
)
It’s the owner’s choice.
Now back to the TicTac blisters…. They show up as the old embrittled antifoul bottom paint is stretched and loses adhesion as the blisters swell. Blisters swell because the bacterial growth in the entrapped moisture generates gasses and gunk… (when ‘popping’ larger osmotic blisters there is a peculiarity unpleasant stench associated with it given the age and volume of the problem).
There is no right or wrong answer to dealing with the problem and it is entirely the owner’s choice.
The owner needs to assess what extent of a problem there is to be dealt with and the anticipated usage style.
The owner has to address their budget and time and options that works for their situation.
The owner needs to understand and monitor their vessel to ensure that it is safe to use, operate and doesn’t become a hazard.
Best Regards,
Over Easy
has finally made her way across the country as well. I’ve completely cleaned her head to toe, fixed a few cosmetic issues in the cabin and got the motor back into shape. We’ve secured a slip at Herrington Harbor on the Chesapeake and can’t wait to get out in the bay. 
)
