Swelling

Definition

Very slow evaporation of residual solvent from a freshly painted paint process. This causes widespread swelling or sweating of the paint surface. Problem can lead to a reduction of gloss (hazing) and in small areas, edge zone marking (see chapter on "Edge-Zone Marking").

Causes

1] Drying time too short between layers in a complete process and/ or too high a film thickness of the filler coat within the process.

2] Filled areas are too thin or are not sufficiently isolated.

3] Swelling of solvent-sensitive substrates.

4] Incorrect quantity of hardener in Body-Filler or Filler coats.

5] Incorrect process when finishing over NC or TPA substrates.

How to avoid

1] Always keep to recommended film thickness and drying times for each product. Where possible dry with infrared as this dries from the lower layers first.

2] Apply isolating coat in sufficient film thickness (circa 50 µm).

3] Before painting, carry out a solvent test with acrylic or NC Thinners.Sand feathered edges and surfaces finely (Body Filler with P80/ P150, Primer Filler with P240 – refer to technical information sheets). Do not apply Body Filler over old paintwork which is solvent sensitive (better to apply to bare metal). Apply sprayfillers in thin spray coats and allow a good flash-off between coats (to isolate). Use products with mild solvent properties (Waterbased fillers).

4] Only use specified mixing ratios.

5] Use Finishing Process S8.

Repair

Thoroughly sand back, or remove the affected area. Refinish with the correct primer and/ or Top Coats.