Wade Blocker on tue 28 dec 99
Tom,
The following is from Robert Fourniers book: " umber is a natural
hydrated iron oxide with some manganese oxide. Allied to ochre and sienna.
Calcined as burnt umber." Use it as a glaze ingredient as you would Fe
oxide. Test it, using small increments until it gives you the color you are
looking for.
Burnt umber molecular weight 284.98. Hope this helps Mia in sunny ABQ
Ivor and Olive Lewis on sun 19 nov 06
Dear Friends,
Burnt Umber has been mentioned as a colouring additive in recent days. =
There seems to be some misunderstanding about its composition.
My first edition of Frank Hamer's Dictionary says nothing about it but =
Kurt Wehlte in "The Materials and Techniques of Painting" lists it as a =
clay substance of indeterminate composition containing Hydrated =
Manganese and Iron oxides.
I have used it to give a dark almost grey black metallic finish on raw =
clay but never to colour a glaze.
Since it contains Manganese it should be treated with a measure of =
respect.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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