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Unknown - Bubbling paint on a GRP bodied classic car

On 4th February 2015, HJ wrote:-

"The problem is Osmosis, common on boats. Moisture has got behind the gel coat. Expensive specialist job to repair and definitely not covered by insurance. "

In response to an enquiry about "Bubbling paint on a GRP bodied classic car" described thus:

"My 1974 GRP bodied classic car was perfect in summer time, and used regularly. When wet weather came in I used two car covers, one soft breathable, and one waterproof, to keep off worst of rain and bird droppings etc.

To my horror the paintwork has bubbled up badly, little humps about 3mm diameter, 1mm high."

IF this is osmosis (which implies that the enquirer is incorrect in referring to "paint") I'd say the enquirer needs to stop using those covers.

Boats are MUCH more exposed to this hazard, since the hulls are continually immersed. They hardly ever show significant osmotic blistering on the topsides, unless its somewhere rainwater is trapped.

If its osmosis it seems very likely the covers are trapping rainwater or condensation against the gelcoat.

Air movement (wind, with maybe some fans inside and/or under the car, if possible, will dry out the structure, and may cause the collapse of some of the blisters.

With boats, a severe case may have the gelcoat stripped, the laminate washed and dried out, and then re-painted with a high-build epoxy/mineral water-barrier coat. That'd be uneccessary on a car, and an acceptable cosmetic appearance would be much harder to achieve.

Asked on 10 February 2015 by edlithgow

Tags: classic cars accident damage used cars honest john classics hj kit

2 answers

peter moss    on 14 January 2017

Yes tell me i owned a Scimitar it had more pimples than a hookers bum !

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