Paint blistering

[Shedding]

I bought a car (privately) in Spring last year and the paint looked pretty good although I could see from signs of masking at the window rubbers that the offside had been repainted at some point. Late last year, the outside temperature was down to -10degC and that seems to have caused some blistering on the offside rear quarter and the front wing. I presume this means it will need stripped and painted again but what could have caused this? Is it just poor paint preparation / conditions or am I going to find body filler (it sounds like metal when I tap it)? Since the door hasn't blistered, does this imply that the paint is OK or might this blister later?

I was going to have some paint work done anyway as the front bumper has some light scuffs so I guess this just increases the work scope. Any idea how much prep and paint for front bumper, and offside in metallic black might be?

Thanks for any help.

Edited by Shedding on Friday 5th January 15:00

[cpszx]

I had something like that appear on my car last year, which i <i>think</i> turned out to be tree sap that had been wind blown across the car. It felt like braille.

I used a little wd40 first just to check if it was errant oil or grease from following something, but in the end, hot soapy water did remove it, as long as it was rinsed while still wet.
If left to dry again, it turned into larger water marks.

I would have a go with something like that first to make sure it's not as serious as you think.

Otherwise, it does look like bad prep and layers were not left to dry correctly beforehand, so moisture has pushed itself out, imo.

[jeff666]

It's micro blister,

a very common problem due to either moisture in the airline when being painted, cheap primer usually celly that has been wet flatted, or a car cover put over the car shortly after it was painted.

It does tend to be the primered areas that go, the rest of the panel will be ok, it will need to be stripped back to bare metal to make sure it doesn't return.

[Shedding]

Thanks for the replies. It's definitely something happening with the paint rather than something being splashed onto the car. I'll look to getting it repainted in the summer by which time I hope anything else which might show will have done so.

[lufbramatt]

As above probably moisture trapped in the primer/ filler under the top coat. I had a bumper on an old car that did the same thing due to it being painted in cold weather. Turns out the bumper had been painted in the cold workshop rather than the heated spray booth, the rest of the car was fine.