Professional Services & Supplies
" It is a paradox of the porcelain enameling industry
that it is less expensive to produce good ware
than to produce an equal quantity of bad ware."
Beneath you will find a comprehensive outline of major enamel defects and their possible causes,
which is mend to simplify
troubleshooting your enameling operation.
Defect | Appearance | Possible causes |
Back-ionization | Localized heavy orange peel |
+ Excessive film thickness + Too high gun voltage + Guns too close to work piece + Low relative humidity of ambient + Poor earthing + High powder receptivity + No AFC used |
Black specks | Blisters or circular holes |
+ Iron contamination + Poor steel quality + Over pickling + Contamination with organic materials + High humidity in furnace + Incompatible enamel combination (2c/1f processes) |
Chrome contamination | Black specks enclosed in a yellow halo |
+ Scaling from firing tools + Scaling from furnace furniture |
Dimples | Slight depressions in enamel surface |
+ Oil or water spots from compressed air line + Contamination by dust from ambient + Contamination by sulphate depositions |
Faraday cage | Burning off due to thin spraying in the angle of sharp corners |
+ Too high charging potential (kV) + Poor product design + Poor particle size distribution of enamel + Excessive amounts of reclaimed enamel |
Gun spitting | Raised areas, sometimes discolored |
+ Powder accumulation around gun tip + Poorly maintained guns + Using compressed air with too high dew point |
Poor powder adhesion | Localized fall off of powder |
+ Poor powder charging + Too many large powder particles + Poor powder storage + Too low charging voltage (kV) + Excessive gun-to-ware distance + Excessive powder recycling + Vibrations / shocks + Interval between powder application and firing |
and the reference book by Silvano Pagliuca and William D. Faust :
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Porcelain (Vitreous) Enamels and industrial enamelling processes, 2011
Ditmer Trading & Consulting BV is a family owned company,
which was founded by Ronald Ditmer in 2007.
We are specialized in providing worldwide know-how, technical services
& equipment to the porcelain (vitreous) enameling.
Ditmer Trading & Consulting BV
Palissander 141
3315MP Dordrecht
The Netherlands
Phone :
+31-78-6169877
e-mail : info@ditmer.nl
Please feel free to contact us for assistance with your (powder) enameling challenges via the form below.