Does anyone know what the chemical composition is of yellow enamel
for ceramics, eg kitchenware?
I ask because I cannot differentiate by visual testing, AU gold
enamel from any other.
I don;t know the chemical compostion of the yellow enamel you
enquire about. However, Thompson enamel co. used to make a marvelous
yellow enamel called Forsythia. It got its name from that flower.
Forsythia enamel had spent uranium as one of its properties. I have
a jar of it, and was concerned about the fact that it had uranium
(spent or not) in it, and contacted Bill Helwig (now deceased), at
Thompson. Bill assured me that there was nothing to be concerned
about—that it had no radio activity. Non the less, I have never
used it for jewelry, and have limited its use to some large wall
enamels that I make. Beautiful color, but was dropped when Thompson
made the switch from lead bearing to lead free enamels.
Alma
In ceramics, enamels, and glass AU is used to create Reds, rose,
pink and purple.
Luster’s (dissolved metals in resinous base) leave a microns thick
metal coating, which looks obviously metallic, or if very thin
iridescent.
Many recipes will make yellow enamel/glazes: Red iron oxide with
rutile, manganese with salts of Zirconium, others used in various
proportions-Vanadium, cadmium, nickel, lead and of course most
famous but no longer legal- uranium (yellow cake).
I am an avid potter who likes to make my own glazes. (OK OK so my
sister taught me!) best regards, Cecelia
Au is not a glass colorant that makes yellow. It is used to make
"gold ruby", which is pink red.
Selenium and (historically) uranium make the most intense yellows.
Iron is also commonly used; the color is less intense.
There is a lot of common ground between glass colorants (my own
personal area of knowledge), ceramic glazes and enamels. But there
are differences too. Temperatures, firing times, fluxes, atmospheric
conditions are all different. These will all affect the final colors.
Rene Roberts
Problem with yellow uranium (and green) glasses and glazes is they
are seriously poisonous - more so than lead. Most enamel glasses have
borax added to keep the liquidus point low but they dissolve in
acids quite readily so shouldnt be used for things that hold
foodstuffs. The same applies to lead oxide glazes and enamels.
Beautiful colours though, arent they? The outside of the Albert Hall
is built of radioactive glazed bricks, caused all sorts of bother
when they acid cleaned it a few years back.
Nick Royall