Enameling (on-glaze decoration)

Enameling 

On-glaze, or overglaze, decoration with enamel colours, fixed by a subsequent firing at about 750C (1380F), gave the painter greater possibilities. Soft-paste porcelains were usually covered in lead glazes which required a second firing, while the use of on-glaze enamel pigments demanded a third. This made them very expensive to produce.

One of the most important types of ceramic decoration is the application of pigments on top of a glazed body. This is known as on-glaze enamelling. The colours are applied by skilled paintresses. Wares are decorated by very gently, sweeping brush strokes. Once the pigment has dried no further work can be done without first firing the ware. Further work can then be overlaid and re-fired.

 

THE COLOUR PASTE

All ceramic colours are oxides of metals. These are mixed with fat oil and turpentine (evaporated turpentine) to produce a paste of even consistency.

FIRING

Firing occurs in a muffle or enamel kiln which provides a closed environment capable of careful regulation. Temperatures are low 700 C - 800 C.

COLOURS

The following metallic oxides produce these colours: 

metallic oxides colour
Antimony
Chromium 
Cobalt
 
Copper
#

Gold 
Iron
 
Manganese
 
Tin
 
Uranium 

- yellow
- yellow
- blue
- green (oxidised) 
  and red (reduced)
- purple
- black
- purples and browns
- white
- yellow

# oxidised is fired with excess oxygen (air) and reduced is fired where there is insufficient oxygen.

BRUSHES

Always known as pencils in North Staffordshire. These vary in type, some having detachable sables. The bristles are usually made of sable or Caucasian squirrel.

OUTLINES

Outlines can be produced on the ware to guide the paintresses hand. 

These can be produced by

China-graph pencils - an outline is sketched which later burns away in the firing.
Printed transfers - these are applied to the piece and the paintress infills with colour.

EXTENDERS

It is sometimes necessary to keep the applied oxides wet. This is usually the case if another colour is to be painted over the first coat. If the initial coat was allowed to dry it would be removed by the brush when the second coat was applied. By incorporating an extender into the colour paste the mix is kept wet for a longer period. Substances commonly used include eucalyptus, oil of cloves, lavender and anis turpens ( a derivative of aniseed.)

 



questions / comments? email Steve Birks steveb@netcentral.co.uk