@ThomasGranmilestone card services wrote:
Hi, I am a retired analytical chemist mentoring a high school teacher in advanced chem. They are using the Raku process of glazing to show multiple colors due to the reduction cycle reactions. My question is can you provide me with the re-dox equations for the various reactions of Cu, Co, Cr, Silica, borate to form various colors.
Thank you
Hello,
The Raku process of glazing involves a fascinating interplay of reduction and oxidation (redox) reactions that create a spectrum of colors. Here are some simplified redox equations for the elements you mentioned:
Copper (Cu):
Oxidation: ( 2Cu + O_2 \rightarrow 2CuO ) (Copper turns green when oxidized to copper oxide)
Reduction: ( CuO + CO \rightarrow Cu + CO_2 ) (Copper can show reds, blues, and greens under reducing conditions)
Cobalt (Co):
Oxidation: ( 2Co + O_2 \rightarrow 2CoO ) (Cobalt oxide can produce deep blue colors)
Reduction: ( CoO + H_2 \rightarrow Co + H_2O ) (Cobalt can give a range of blue shades)
Chromium (Cr):
Oxidation: ( 4Cr + 3O_2 \rightarrow 2Cr_2O_3 ) (Chromium oxide gives green color)
Reduction: ( 2Cr_2O_3 + 3SiO_2 + 3C \rightarrow 4Cr + 3CO_2 + 3Si ) (Chromium can produce pinks and reds under reducing conditions)
Silica (SiO2):
Silica does not undergo redox reactions in glazes but acts as a glass former.
Borate (Borate compounds like B2O3):
Borate compounds are also not typically involved in redox reactions but act as fluxes to lower the melting point of the glaze.
These reactions are highly dependent on the firing atmosphere, temperature, and the presence of other elements. The actual color development is quite complex and can vary with the specific compounds and the conditions of the Raku firing process.
I hope the information may helps you.
Best regards,
Yvonne Rhodes
