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Blisters on GFK bodywork


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#1 funformula

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Posted 09 December 2011 - 22:49

The paint on the GFK bodywork of my Reynard F3 car is covered with lots of small blisters (2-5mm)
The reason for this may be, that the car is stored in a place with sometimes high air humidity.
When I cut the blisters, there is a yellow/brown liquid inside.
The blistering only appears on the GFK parts not on the carbonfibre-monocoque.

Does anyone has the same problems or know the reason for this?
I like to paint the car in new colours and don´t want to happen the blistering again.

Thanks for all thoughts and answers.

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#2 Lee Nicolle

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Posted 09 December 2011 - 23:06

The paint on the GFK bodywork of my Reynard F3 car is covered with lots of small blisters (2-5mm)
The reason for this may be, that the car is stored in a place with sometimes high air humidity.
When I cut the blisters, there is a yellow/brown liquid inside.
The blistering only appears on the GFK parts not on the carbonfibre-monocoque.

Does anyone has the same problems or know the reason for this?
I like to paint the car in new colours and don´t want to happen the blistering again.

Thanks for all thoughts and answers.

Sure the car was not painted originally with moisture in the airline/tank? It usually shows fairly soon but sometimes not for a year or so.
A good filter/trap cleaned regularly and the compressor drained regularly is imperative for decent paint work.

#3 funformula

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Posted 09 December 2011 - 23:38

Sure the car was not painted originally with moisture in the airline/tank? It usually shows fairly soon but sometimes not for a year or so.
A good filter/trap cleaned regularly and the compressor drained regularly is imperative for decent paint work.


I own the car since 1994 and it shows no signs of blistering until 2005 when i stored it in the current place, which has a high level of air humidity sometimes.


#4 Greg Locock

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Posted 10 December 2011 - 01:31

Do you know what paint system was used?

#5 Wolf

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Posted 10 December 2011 - 02:35

I think this might be the problem of moisture absorption (I seem to recall older glass-fiber boats used to suffer from it)- polyester resin (which might have been used in GFK bodywork, but carbon tub would've been made with epoxy resin which AFAIK doesn't suffer from this problem) was said to be quite suspectable to it.

p.s. I have encountered a minor occurence on our family boat below the water-line, and we sanded, buffed, &c the affected area and applied a thin coat of epoxy based enamel (as sort of gel-coat substitute) which seemed to prevent any further occurence (and that was over 20 years ago)

#6 ray b

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Posted 10 December 2011 - 03:23

boat pox or fiberglass pox

funny it only strikes certain year boats
the older 50-60's boats seldom have problems
thick gel-coats and heavy layups used then

70-80's boats it is much more common
esp on thin layups with thin gel-coat [resin prices follow oil]

I have heard where the boat was made matters
lots more problems in wet humid areas then dryer ones

are both sides of your glasswork painted ??
drying a few weeks in a hot dry place can help
and repaint BOTH sides

newer vinylester resin is claimed to be better then poly


#7 Magoo

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Posted 10 December 2011 - 14:58

Your description paints a picture of disappointingly uniform blistering over the entire vehicle, rather than localized in particular areas. If so, the technical name/description is osmotic blistering aka laminate hydrolysis. It is due to two things: 1) H2O molecules are small and 2) it is virtually impossible to remove all the air voids created in fiberglass layups. So into these voids water and water vapor are drawn in capillary fashion along the glass fibers. As this moisture creeps in it combines with the water soluble materials in the layup left behind after the original catalyzation. (Acids, glycols, other nasty stuff). This acidic solute, or crud if you will (the polyester vinaigarette you discovered) collects in the voids because the H2O molecules are small enough to get in, but the crud molecules are too big to go out -- producing the characteristic pustules or boils which swell and fracture the paint surface. The only fix is to completely strip, seal, and refinish with current & proper materials, in which case it will not come back.

#8 funformula

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Posted 10 December 2011 - 22:14

Thanks for the response.

Today I´d been told that the reason may be the use of Diethylentriamin (DETA) in the 2K Laminate. In the GFK-Laminate producing business there were problems with blistering since about 4 years.
The blisters are filled with a yellow/brown liquid (same as on my car) and appear about 6 months after producing the part.
BUT: My car was built in 1991 and the GFK bodyparts don´t show signs of blistering until 2005. But if the problem is caused by DETA, why not already in 1991?

@Wolf:
I also heard that boats sometimes suffer from "blistering" and that is caused because of moisture absorbtion (osmose) as you describe. But these blisters are usually filled with water and not the strange brown liquid.

I´m still confused.