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Sinkage

Definition

Very slow evaporation of residual solvent from fresh paintwork. This causes widespread sinkage of the paint surface, which can result in loss of gloss (haze) and also in localised edge markings/mapping. (see ‘Edge marking’).

Causes

  1. Drying time too short and/or excessive film build of filler or entire paint system
  2. Body-filled areas are too thin or not sufficiently sealed
  3. Swelling of solvent-sensitive substrates
  4. Incorrect quantity of hardener used for body filler and filler
  5. Incorrect paint system used for TPA substrates
sinkage
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Beigefallen
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How to avoid

  1. Keep to recommended film builds and drying times. Drying with infrared equipment will prevent sinkage of the paint film as the lower paint layers are dried first.
  2. Apply a sealing coat in appropriate film thickness (approx. 50 µm).
  3. Before painting, carry out a solvent test with acrylic and/or NC thinners. Sand feathered edges and surfaces carefully (body filler with P80/P150, primer filler/filler with P240 according to technical data sheets). Do not apply body filler to old, solvent-sensitive paintwork (leave a bare metal transition area). Apply filler in thin coats (for sealing) and allow longer flash-off times between coats. Use products with mild solvent properties (for example, waterborne fillers).
  4. Keep to specified mixing ratios.

Repair

Thoroughly sand down affected areas. Refinish using the recommended undercoats and/or topcoats.