Lumps

Description of defect

Lumps are common enamel defects, which are characterised by rounded raised areas with typically a diameter between 3 to 12 mm.

Occurrence

This phenomena may occur at both wet & powder enameling processes.

Possible Causes

Possible causes for lumps in random order :

• Drips of enamel slip (wet)
• Dried enamel particles falling from equipment and/or tooling (wet)
• Incorrect spray gun settings (wet)
• Worn out gun needle, nozzle or packings (wet)
• Gun spitting (powder)
• Powder deposition on gun deflectors (powder)
• Incorrect fluidity of powder enamel (powder)
• Oversized enamel particles (powder + wet)