Paintwork Question

[ktnez99]

My Z has had “work” done recently and the rear quarters have now been covered with reptilian-like bubbles. I’m wondering how these have been caused as they are only on the rear quarters and nowhere else. Here’s a close-up photo to show you what the top of each rear quarter looks like.

 

[RickyBobby]

Hopefully this helps explain it

Common Causes for Post-Respray Bubbling:

• Moisture Contamination: Water trapped in the paint or on the substrate during application creates "osmotic" blisters.
• Improper Drying: Solvent gets trapped when new coats are applied before previous layers have fully evaporated/dried, especially with low-quality thinners.
• Surface Contamination: Grease, dirt, or wax was left on the panel during preparation.
• Humidity/Temperature: Painting in high humidity or in extreme hot/cold conditions.
• Low Film Thickness: Thin, uneven layers of primer or topcoat can weaken the paint structure.

 

[Duncodin]

I've had that many times when I've rushed a job.

I see that on filler or pimer that has been wet sanded and not allowed to dry fully before primer/paint. Sealed in the moisture vapourises expands and you get little bubbles

 

[ktnez99]

Both interesting responses, thanks. I had the car painted about 5 - 6 years ago and this bubbling only appeared directly above where the rear top struts required welding. Nowhere else on my car nor at any other time since the car was painted and during the 5 - 6 years since. Would this have appeared before the welding was done? The rear quarters were not removed so the welding took place from under the arches where this bubbling is and from the boot area where the boot lid was removed.

 

[Duncodin]

You never mentioned welding. I don't know what car it is or how close the welding was to painted body work but yes paint will blister if there's a lot of heat from the weld. Also sparks from the mig welder can fly some distance landing on paint but in my experience such sparks would cause tiny burn dots on the paint not blisters. Or maybe after the welding sone paintwork needed redoing quickly.

 

[ktnez99]

@Duncodin Yes, welding of the two rear top struts. What I can’t figure out is if the bubbles were due to the paintwork, wouldn’t they have appeared during the past 5-6 years? The welder failed to cover the car up; for example, there’s paint on the driver’s inner door card splattered all over which needs removing as well as a catalogue of damages. So, imagine the two rear struts of your Z - yes, it’s s Z3 I’m talking about - were cut out and replaced without protecting the body of the car from welding sparks, heat, etc. then that’s what happened to my Z.

 

[Paul Rice]

I have similar on the roof of my MGB started to appear last year some 14 years after its full re spray