These are beads, droplets or even large globules, socalled “curtain effect” which have run vertically down the panel.
1. The nozzle on the spray gun was too large.
2. The spray technique was not suitable for the material. The material application was too wet because the gun was too close to the object or the spray movement was to slow.
3. The coats of paint were applied too thickly.
4. The flash off time between individual coats was not long enough.
5. Thinner or hardener was too strong for the particular spray conditions. This happens particularly when spraying small areas, or in low spray temperatures.
6. The paint was mixed too thin.
To avoid the formation of runs it is necessary to observe that the spray guns, application technique and the adjustment of the paint materials are suited to the spray conditions, i.e. use correct hardener and reducer to suit the existing conditions. Where necessary use a smaller nozzle with better atomization and faster thinners.
Small runs can be removed once dry with a paint nib plane. Then rub down with P 1000 - 1200 paper and finally polish with fine polishing paste and high gloss polish. Large areas of “curtaining” must, however, be completely sanded down and refinished.