First, If you look under Resources at the top of the page, you will find a list of casting companies.

Second, purchase Thompson Enamel Workbook - which is filled with all the scientific information you need to proceed with metals and enamel.

They give you an extensive break down of metals suitable for enameling and their combinations of alloys and compatibilities.

Third - Opaque enamels work well over gold, but normally are used only for accent. Why waste the precious gold if you can't see it? If you want a gold look - use gold foil -

Transparent enamels are usually used on gold so that you can see the shimmer of the gold underneath.  I believe 18 kt. it the preferred choice. 

Gold is frequently alloyed with silver, copper, zinc, platinum, palladium, cadmium, nickel etc. to decrease its cost, increase its hardness or to change its color. Normally only the alloys with silver, copper, and occasionally platinum or nickel are used for enameling. Each of the alloy will hae a different solidus point, coefficeint of expansion, modulus of elasticity, oxidation characteristics. etc.  The color of transparent enamels applied over the alloys will be affected by the change in oxidation characterisitcs and the amount of oxides dissolved.

Both transparent and opaques wil be affected by the change in expanion and modulus of elasticity of the metal. Additions of copper increases both the modulus of elasticity and expansion. Additions of silver reduces the modulus of elasticity oand increases the expansion far more than copper additions.Thus as copper additons increase enamels with expansions in the lower ranges should be eliminated and total thickness of coating should be reduced.

As silver additoins increase it is wise to use higher expansion enamels, however the lower modulus of elasticity resulting from the silver additions make the system a little more firgiving as to thickness of application and range of permissible expansions Even though an enamel color works well over gold there is no reason to assume it will work on a gold alloy. And one which fits a gold-silver alloy may chip off a gold- copper alloy. The reason is not an an alloy which is no good, but an enameler who selects enamels by color with no attention to the primary properties, firing temperature and co-eficient of expansion.

Many proprietary casting alloys contain a small amount of zinc as a deoxidizer. It also produces a fine grain casting. If the zinc additions are appreciable, the solidus temperature will be reduced quite rapidly. As little as 4% zinc lowers the solidus point enough to prohibit the use of normal enamels used on copper. More than about 27% zinc prohibits the use of any enamel normally available.

I just purchased what is called Pink Silver - a combination of silver, copper and 3% zinc - Thompson believes I might be able to get away with that percentage if I don't fire too many times . We shall see.

Depletion guilding is used for Sterling Silver to bring up the fine silver to the surface in order to enamel on it. Nitric acid also does the same thing- 

[blockquote]Julie B said:

Hello!

I was just wondering if depletion guilding the 18K gold would eliminate the zinc issue?

Best Regards,

Julie

[/blockquote]

Hi Julie,

I am not sure my reply went through, so I am going to answer again -

I spoke with Rick McMullen at the Enamelist conference about your questions on gold and zinc - he works almost exclusively in gold and has his gold made up without zinc. You might consider that!