David Hendley on wed 24 jul 02
Boron will make copper red glazes go towards blue.
If the copper red color is fully developed it's not very
noticeable, but if the red fails what you are left with
can look blue.
Boron is supplied by Gerstley Borate or a frit in many
copper red glazes.
Magnesium can also tend to make copper red glazes have
a bluish hue. It is usually added to the glaze by dolomite
So why use copper red glazes containing boron and/or
Because they supply other desirable properties, such as
earlier sintering and melting, and a high coefficient of
expansion, which reduces crazing in the fired glaze.
----- Original Message -----
Sent: Wednesday, July 24, 2002 4:50 PM
Subject: BLUE COPPER RED
> Does anyone know what causes copper reds to come out more of a blue color
> with only slight red tints? I am using an old glaze i have used a lot but
> a new kiln, and it never came out blue in the old kiln, except for a
> tints of blue. I know it was on extremely thick, so maybe there was too
> copper for a red; but other than that i am trying to find an explanation
> go back to a different copper red i used at one point. Any ideas?