Glass On Metal, Volume 13, No. 6, December 1994
by Woodrow Carpenter
On the back cover you will find an announcement for a lead free opalescent enamel. More than three years of work has gone into its development. If a few simple procedures are followed consistent good results are obtained.
When fused directly onto copper it should be fired at 1500 degrees F. for approximately 4 minutes. It will appear as a well cleared transparent flux. Opalescence can be produced by reheating at 1500 degrees F. for approximately 1-1/2 minutes. The time is critical. If too short no opalescence will develop and if too long the opalescence will vanish. The preferred procedure is to refire for 1400 degrees F. for 3 minutes. The opalescence develops as the ware cools. Those who prefer to coat one side at a time can fire the first side at 1500 degrees F. for 2-1/2 minutes, cool, pickle, coat second side and fire at 1500 degrees F. for 4 minutes. Then refire as above to develop the opalescence.
On silver first apply a good coat of flux made for silver. Then apply the opalescent enamel and fire at 1400 degrees F. for 2-1/2 - 3 minutes. As it cools the opalescence will develop.
Enamelers who like to fire high can do so to obtain different colors from the dissolved copper oxide. Then refire at 1400 degrees F. for 3 minutes or at 1500 degrees F. for a short time as described above.
The announcement also includes an enamel to be used as opalescent lumps. Again, certain procedures must be followed for best results.
1. Dip the lump into a solution of Klyr-Fire or other adhesive.
2. Place onto a fired enamel surface and allow to dry.
3. Fire at 1400 degrees F. for 2-1/4 to 2-1/2 minutes. Lump should be well rounded and quite opalescent.
The lumps have thermally reversible opacity. If refired at 1400 degrees F. for 1-1/4 minutes they will become quite opaque. Further refiring at 1400 degrees F. for 2-1/4 - 2-1/2 minutes will change the opacity to opalescence. Of course too much fire will flatten out the lump so it will be more of a domed disk. If opalescence is lost, refiring for a shorter time will bring it back. With judicious firing considerble latitude is obtainable.
Link to Opalescent Enamels in ThompsonEnamel.com