Drying

Blistering

Raised bubbles and blisters on the paint surface - single or extensive. Moisture or dirt trapped between the layers pushes the paint system from the inside.

Cause

Application of varnish on acidic or reactive primer without checking chemical compatibility
Polyester putty applied directly to the reactive primer
Wet sanding of polyester putty - polyester materials absorb water and release it for years
Moisture condensed between layers with a large temperature difference between the body and the cabin
Insufficient evaporation of water-based products before applying the next layer
Contaminated air in the compressor system - water or oil entering the gun
Opened or poorly stored products - absorption of moisture from the environment before use
Too short cross-linking time between layers - insufficient chemical reaction of the hardener
Poor mixing ratio - too little or too much hardener results in incomplete hardening
Improperly mixed product - Inhomogeneous chemical reaction leads to weak spots in the layer
Painting at high relative humidity without adequate ventilation and cabin heating
No acclimatization of the cold element before painting - the cold surface condenses moisture from the warm cabin air
Failure to comply with the dew point conditions - the surface temperature of the element is too close to the dew point temperature of the air in the cabin, which causes invisible condensation directly on the painted surface

Prevention

Substrate preparation

Check the compatibility of all products before application - do not combine reactive systems with epoxy ones
Sand polyester putty only dry - never wet
After wet sanding (polyester-free products), wash the substrate thoroughly with clean water and immediately dry it with compressed air
Before painting, wait until the element reaches the cabin temperature - at least 30 minutes of acclimatization for large elements
Clean the substrate thoroughly with remover before each subsequent layer - avoid contact of hands with the cleaned surface
Apply the base only on recommended primers, interlayers and fillers

Working conditions

Check the dew point before starting work - the surface temperature of the element must be at least 3°C above the dew point
Do not paint at relative humidity above 80%
In cold and humid conditions, always allow the item to acclimate to the cabin before painting.
Drain the water from the compressor and tank regularly - preferably daily before starting work
Regularly check and replace filters in the compressed air system
Maintain a constant temperature in the cabin throughout the drying period - avoid temperature fluctuations

Application and storage

Observe the flash-off times between layers given in the product data sheet
Evaporate water-based products until they are completely matte and dry before applying another layer
Mix the products thoroughly and in the recommended proportions - use a scale or measuring cup, do not estimate by eye
Close cans tightly immediately after use - opened products absorb moisture from the air
Store products at the recommended temperature and avoid temperature fluctuations - especially in winter
Keep tools and equipment clean - a dirty gun or dirty hoses can introduce moisture into the system

Repair

Determine which layer has blistering before repairing - check by pressing gently and observing
Sand the paint system down to the layer where the problem occurred - do not cover the defect with subsequent layers
If blistering occurs at the edge of the putty or primer, it is necessary to remove the entire metal system
After sanding, dry the substrate thoroughly with compressed air - especially in corners, grooves and strips
Before rebuilding the system, eliminate the cause - check the dew point, cabin humidity and product compatibility
Rebuild the system according to the technical data sheet, observing flash-off times between each coat
Do not accelerate drying with the IR lamp too aggressively - rapid evaporation may cause the defect to recur
After repair, monitor the surface for several days - blistering may reappear if the cause has not been completely removed