Curling / Lifting / Swelling / Wrinkling / Crimping / Paint Crazing

The material surface becomes wrinkled or swells. This appearance is also seen when, for example, acids or paint strippers come into contact with coatings.

• Sources of defects:
  • The substrate has not been properly dried. The risk of dissolution by subsequent materials is possible here.
  • The trapped solvent penetrates into fresh coating from below when heat is applied.
  • The material is hard or attracted on the surface and there are residual solvents in the substrate. When fresh solvents hit such surfaces, it is easy for them to penetrate the coating and drive a reaction in the substrate. Here the solvent from the last applied coat penetrates the middle coat and gets into the substrate, this process is called diffusion, and the solvent attacks the underlying material, thus increasing the volume and the material starts to puff up, curl or wrinkle.
  • Vulnerable old coatings such as 1-K NC or TPA (thermoplastic acrylic paint) are overcoated with systems that contain a lot of solvents.
  • The possible build-up of stress between two systems in the wet-on-wet process.
  • Excessive film thicknesses in the subsequent application, the high solvent content pulls into the lower gelled layers and attacks the material.
    2-component systems in the gelling phase Wet-on-wet overcoating.
  • Many 1-component materials can be dissolved or dissolved with solvents. Similar to graffiti, which could be removed with solvents (no recommendation – observe environmental protection regulations!!!), the coatings are attacked and the coating decomposed. In this condition, they can be removed with a solvent-soaked cloth. Depending on the substrate, complete removal may be possible (dense substrates such as glass) or only fragmentary removal (porous stone or similar).
• Error prevention:
  • Dry substrates properly. If the ambient temperature requires it, dry individual layers with IR (infrared) and follow further work steps.
    Test substrates with the solvent test before coating.
  • Apply material thickness according to technical information.
  • If possible, do not sand through filler layers and insulation primer. At these points, solvent penetration into the substrate is favored.
    Observe flash-off times according to specifications.
  • Do NOT overcoat coatings in the gelling phase. In this case, drying and sanding must be carried out.
• Repair route:
  • Sand down to the supporting substrate and start a new coating build-up.
• What happens during crimping?
  • Solvents from the last coat are applied to penetrate the substrate and „break“ the chemical cross-linking, resulting in an increase in volume in the substrate and dissolving of the substrate. The substrate loses adhesion and „swells“.