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Blisters and bubbles on your car's body spell the end for the paint in that area.
The good news is that we can strip blisters back to bare metal, refinish them, and repaint them to a standard indistinguishable from a factory finish.
It's best practice to respray the whole panel to fix paint blisters because slight variations in application technique, paint thickness, and environmental conditions during drying can result in noticeable differences between the repaired area and the surrounding paint (which is why some smart repairs look so bad!).
Having said that, localised paint blister repairs on a car can work if the paint is flat and there isn't any underlying corrosion.
Why do paint blisters happen?
Paint blisters happen when air or material gets trapped behind the paint, pushing the paint layer outward. The blister might look more like a bubble, worsening over time and with heat due to the metal expanding.
Old and new cars are susceptible to paint blisters, but for different reasons. Rust is a prevalent cause of blisters in older cars. As the metal corrodes, it expands, pushing the paint outward. Improper body filler application or inadequate surface preparation during previous repairs can also lead to blistering.
Newer cars can have errors in the factory painting process that cause blisters, such as contamination or improper paint mixture. Bird droppings and tree sap can also damage modern clear coats and cause blistering.
Are paint blisters a major concern?
Paint blisters are a valuable diagnostic tool, alerting us to underlying problems that might go unnoticed until more severe damage occurs.
Car paint blisters tell us that the coating is failing, but the reason for failure could be local, such as a stone chip or a poor previous repair. These are not a concern.
More systemic problems, such as widespread corrosion, give us more cause for concern, but there's always a fix, so don't worry too much.
Repairing paint blisters on a car
Longmynd provides car body paint repairs that fix paint blisters for good. Here's what you need to know about repairs:
The wrong way
A favourite technique of car dealers (some might call them unscrupulous dealers) is hitting a paint blister with a polishing compound and rotary machine to flatten it and make it near-invisible to the naked eye.
Unlike scratches, polishing out a paint blister is a temporary fix. It only works for blisters not caused by underlying corrosion—hitting a corrosion blister with polish will rip through the paint and make the problem look 100 x worse.
The correct way
The correct way to repair car paint blisters is with new paint.
However, to prevent recurrence, we must investigate and address the root cause instead of just refinishing the surface.
There are two checks we'll do:
- Run our hands over the paint to 'feel' for the blister and reveal any underlying texture changes to the metal and primer.
- Take paint depth readings to check for over-polishing and compounding, previous repairs, and signs of a poor factory finish.
However, most of the diagnosis is based on experience – the blisters we've seen before and the hundreds of repairs we've made.
We'll then perform a repair. This will be either:
A complete refinishing of one or more panels, stripping the finish back to bare metal and repainting to factory standards.
An isolated repair to the blister area, using tape to create a repair zone and removing the affected paint to replace it with new.
We prefer refinishing the whole panel because it provides a uniform finish and is not a noticeable repair.
The repair process
For a complete panel respray:
Step 1: Prep
We'll clean the entire panel thoroughly and sand down the affected areas, removing all paint and primer from blistered spots. If rust is present, we'll remove it completely using mechanical or chemical methods.
Step 2: Priming
All bare metal receives a high-quality primer for the entire panel. The primer is allowed to thoroughly dry, sanded smooth, and the surface is etched slightly – this provides an ideal surface for new paint to adhere to.
Step 3: Painting
We mix paint to match your vehicle's colour code and spray multiple thin coats of base colour, allowing each coat to dry thoroughly. OEM paint is typically 125um thick (~5mils) – we aim to replicate this plus 10% for quality's sake.
Step 4: Clearcoat
Once the base coat is dry, we apply clearcoat in multiple layers to protect the paint and produce the correct finish. Most cars have a gloss finish, but we can also use a matte or satin clearcoat, depending on the finish.
Step 5: Curing
We let the new finish dry naturally or use UV LED to cure the paint in the case of photo-sensitive paint finishes. UV curing significantly speeds up the delivery time and hardens the paint beyond a natural drying cycle.
Step 6: Polishing and finishing
The last step is polishing the newly painted panel to create a flawless finish. Depending on the car's condition, we can also give the rest of the car a one-stage polish to make it appear as though the old and new paint are the same.
Summing up
Don't tear your hair out over paint blisters on your car. They are repairable by refinishing the panel or, in some cases, via a localised repair. The main challenge is ensuring the new and old paint matches perfectly.
We repair car paint blisters and other defects on new and old vehicles.
Contact us to get started.