| You are technically helpless in some ways when it | | | | decorating kiln temperature. This may cause blistering |
| comes to gelding. You are at the mercy of your gold | | | | of the gold or other problems. The gold emulsion |
| supplier. Preparations of gold emulsions used in | | | | supplier can make the emulsion more suitable for |
| ceramic decorating are prepared in secret. Any | | | | higher firing.So the problem is glaze control.Why do |
| technical problems relating to the emulsions used | | | | you have variation in the hardness of the |
| must be resolved by the gold vender. Also, the | | | | glaze?Remember that we are talking about fusibility |
| emulsion suppliers often adjust emulsions to resolve | | | | here.Most fine china glazes are lead based. Lead |
| problems not caused by regularly used emulsion | | | | bisilicate is a lead frit commonly used. It is make in |
| formulations.Gold and other precious metal emulsions | | | | large batches and the specific gravity of each batch |
| are used in the ceramic industry to add value to a | | | | is different. Therefore the laboratory at the factory |
| product. This is usually in the form of banding or hand | | | | must calculate the lead content of a glaze made with |
| painting. Banding can be by hand or by machine. On | | | | a particular frit batch. If the lead content is too high, |
| firing, the gold must sink to the proper extent. It is | | | | then the lead bisilicate must be cut back. If the |
| called soft if it easily abrades off with a pencil eraser. | | | | calculated lead content is too low, it must be |
| If it sinks too far into the glaze and looses its ability | | | | increased.The best control for the glaze itself is the |
| to be buffed to a fine polish, it is called hard.Hard gold | | | | FIRED specific gravity. Fire a cup of glaze, break out |
| can be caused by soft glaze. That is the glaze is | | | | a chunk, and measure the specific gravity. Use this as |
| more fusible than usual. The decorating supervisor | | | | a control procedure.To maintain better control, blend |
| tells the lab that the glaze is soft, lowers his | | | | frit batches before glaze formulation to even out the |
| decorating kiln temperature, and hopes the next lot | | | | composition. Work with your suppliers to standardize |
| of glazed ware will not cause him more problems.Soft | | | | their materials. Blend glaze batches to get the right |
| gold from hard glaze causes him to raise his | | | | glaze hardness. |