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Comment by Norm Stuart on June 3, 2019 at 7:03pm

Many of us occasionally use reliable commercial Cone 04 metallic glazes with creating either a shiny gold or shiny silver color.

I've adapted a recipe. Sorry,  the bad news is it's leaded (like similar commercial glazes).

The tile in the middle is my reference recipe Leaded Gold.The tile on the left is a "Silver color" created with twice the amount of cobalt oxide.

The tile on the right has 3% added Lithium Carbonate, displaying the distinctive crackle of Clay Planet's "Aztec Gold".

I had hoped to replace the lead in these recipes with bismuth, but in short that's not possible.

Bismuth melts at a lower temperature than lead and when the vapor condenses last back onto the ceramic it turns the shiny metal color from the manganese into a shiny bismuth black.

My imagined understanding is the cobalt, nickel and titanium all create a dark and imperceptibly crystallized surface onto which the manganese vapor redeposits. The glaze may need to be alkaline with soda ash, pearl ash or lithium to reflect gold or to have a glassy enough surface to appear metallic. Who knows if that's a good guess.

There appears to be a way to make an unreliable Cone 04 metallic gold glaze without lead, similar to the unreliable Spectrum gold glazes. Half 3134 Frit, Half Manganese Dioxide, and something like 5% soda ash, or lithium carbonate or pearl ash, all suspended with bentonite. I'll work further on the percentages. By comparison it's disappointing, but it does not have lead - just manganese which toxic enough.

Adding more than double the cobalt turns it black as does adding any iron. Why all the Cone 6 gold glazes use Red Art Clay is a mystery to me, it doesn't help this recipe.

Here's the original recipe on the left and my pretty close lead bisilicate frit recipe I'll try next, now that the lead frit is back in stock.