[Clayart] About making a red glaze work again.

[William Schran]

I learned many years ago that iron reds (at least the oxidation ones)
needed controlled cooling with a hold in the 1900F range. They also
seemed to work better when applied on the thicker side.
I discovered this back in the early 1980's firing a larger vase form
with an iron red glaze. The piece came out of the firing with various
shades of brown, no red. Soon after I read an article, probably in
Ceramics Monthly, about iron red glazes and finding the red color by
refiring glazed work in a bisque firing. I gave it a try and it
resulted in the glaze turning a deep dark red where the glaze was
applied thicker and lighter glossy brown where thinner. From this I
realized the glaze would need controlled cooling. Of course back then
our kilns were all manually controlled, so controlling the cooling
required being present to closely monitor the firing.
On Digitalfire I found this:
https://digitalfire.com/material/tricalcium+phosphate.Tri-calcium
phosphate is a synthetic bone ash, but the chemistry may be variable.

Bill

William Schranwschran at twc.com703-505-1617

	-----------------------------------------From: "Roxanne Hunnicutt via
Clayart" 
To: clayart at lists.clayartforum.com
Cc: "Roxanne Hunnicutt"
Sent: Saturday July 27 2024 7:52:15AM
Subject: [Clayart] About making a red glaze work again.

 My red stopped working before Covid. I still have not managed with
 different red iron oxides to get it again. Now we have contacted
Stephen
 Hill and learned his newest revision. But I’m confused by this:
 Tri-calcium phosphate is the same as bone ash?

 Is that so? Or is it a substitution? I bought some Tri-calcium
phosphate
 for the garden. What is best?

 Help me get my red back.

 Rox
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