John - Is your commercial burnish gold product:
a black colored Gold Sulfide (with or without bismuth or other fluxes),
or colloidal gold in a resin?
ionic gold in a red sulfonated oil?
or a different product which doesn't firing?
I've previously tried gold leaf, but I haven't found the right cone. Too hot and I just end up with a pink glaze, yet too cool and it doesn't stick to the previously fired glaze. Palladium leaf fired too hot does create a beautiful iridescent surface. I've assumed I can't use anything other than gravity to hold the gold leaf in place, or can you place a layer of something over the gold-leaf which would fire-off?
I'm under the impression that gold lusters are somewhat more durable, due to the thin film of Rhodium which floats on top of the gold. But admittedly even this gilding can be removed with a eraser containing grit.
My understanding of gold or palladium luster is that various metal ions are attached to sulfonated oil (by mixing acidic gold chloride and other metal chlorides with Turkey Red Oil or sulfonated laurel oil). This gold product by itself would be Gold Dodecylmercaptide, but I believe Bismuth, or Vanadium (also attached to sulfonated oil) are also added as a flux to help the gold adhere to ceramic, along with the sulfonated Rhodium metal for hardness and durability. But maybe this is just the formulation for "Brught Gold" using the Rhodium to create a "metal mirror".
Most of this information is from declassified military research from WW-II when America was cut off from gilding technology known only by German ceramic makers (it was needed for war electronics). I don't have much information on anything newer as ceramic luster manufacturers don't make a habit of publishing their trade secrets.
The only other technology I've seen referenced uses the inclusion of up to 2% organic silicon molecules in the mix. The organic silicon molecules burn-out to silca intermixed with the gold, interfering with the conductivity of the gold thus making it safe for microwave use. It's not mentioned, but I seems like the intermixed silica in the gilding could also impart a hardness and durability to the gold layer? Any ideas or experience would be appreciated.
We recently saw some beautifully gilded porcelains in the Neuschwansten museum, probably made with fired gold mercury amalgam, but even these very thick gold coatings had been scratched and worn through with use. Yet, so far as I know, any glaze placed over gilding just give you that expensive pink glaze.
I've tested the bright and premium from them in the past. The premium has a higher gold content.... more durable and a tad less "bright".
Personally I like less "shine". Hence the use of the burnish gold. (It is hard to find other than from majore ceramics dinnerware manufacturers. I got exposed to burnish gold many, many years ago when I was doing glaze development consulting for a major archetectural ceramics company. ( http://www.sherlewag...oe11-25gp-pl/?f= )
I am currently using a burnish gold material from a commercial level supplier...... very high gold content. But very expensive and a huge minimum purchase.
Personally I'd go for the Premium. "You get what you pay for."
Here's the burnish lustre: