... as I was saying.
I cannot think of any obvious yellow pigment that might be involved, although I do feel that
iron might well be involved somewhere.
Looking at the differences between bar 4 and bar 5.
MgO down 1.-7 -> 0.55, Fe stable 0.17 -> 0.16, TiO2 up 0.03 -> 1.06
Which sort of argues for Ti involvement.
Well TiFe2O5 (pseudobrookite) is certainly yellow enough, as seen in "marbled terra sigillata"
... I would love to hear of any other slip or glaze that uses pseudobrookite as a colourant, and
the conditions under which it can be reliably produced.
It would be nice if the colourant was an Mg compound. Magnesium ferrite (MgFe2O4) is a potential
candidate, but I've usually seen it mentioned as a reddish brown colour:
- as an oil colour
- as an iron-red glaze
Although the colour is described as "presenting a yellow-orange color" here:
Anybody have any thoughts on candidate yellow pigments, and why it only appears in one of the test bars?
Added: This paper suggests that getting pseudobrookite to work as a yellow ceramic pigment isn't that easy,
with a tendency to produce browns.
- High Bridge Pottery likes this