Bill Edwards on fri 1 aug 03
I think iron reds can be really a great glaze when
they go right, just like the phase seperation of
floating blues. I would make a hypothetical statement
here but its best to leave that one alone. I have
spent many years and countless tests looking for the
best choices in iron red. I like the color response of
Randy's Red but it has some minor durability issues
even though iron wouldnt be considered a major threat
(Food service wares)in my opinion but some color
shifts during use might be expected. Changing the
glaze formulae seems to alter the color in this
particular recipe. Re-firing some irons can make them
brighter such as what I seen in the last firing I done
where I dropped the heat down and ramped back up and
held and let it cool normally. But after several
variations in working with this method, I am still not
100% pleased. I have way too many samples of bad or
inconsistent iron oxides but the one I do use most
often has yet to be replaced by the supplier with one
of like quality. (Same story as always, they take what
they can get)Most times I feel they don't know or they
don't order from the same supplier based on costs?
Currently I believe I will buy my next load direct
from the manufacturer since I am more used to doing
business that way. I would be happy to do that if I
knew I could re-sell some of the iron since bulk
quantity comes to mind. This would be after me testing
the product and also holding the producer down by the
toe and making sure it tests out upon shipment and was
from the same lot and of course came with the product
analysis and purity of content.
Finding a good grade oxide pigment is one of the key
factors in producing bright iron reds. I am still
amazed that few have really pushed their suppliers in
providing them the content information on their
chemicals and in particular the coloring oxides that
make a huge difference in the end results of the fired
product. Consistency is rare in our work all too often
because our suppliers sell us what they consider a
bargain and thats what we drive them towards. But it
matters in the end what condition our materials are in
and it reflects in the finished product.
I have looked at the various forms of iron and their
uses and wanted to share some of this with those who
are working with ^6 oxidation iron reds and still
looking for ways to enhance what this wonderful
colorant is capable of. Maybe this will help take some
of the suspense out of iron so we can get those reds
out. Bone ash additions are supposedly another method
to get brighter reds from iron or rather the addition
of phosphorous. I will eventually test this out once I
settle on a suitable iron and a supplier that is
concerned as I am with consistency.
If I knew when I purchased samples, and if the
supplier would give me the time I would simply buy a
vast amount to last me most likely the rest of my
life. I just hate having to do that since too little
space and all too often too many other things can
happen that can cause me to lose the material I
cherished so much. Remember, It wasn't long ago I
lived through the worst flood ever and lost 3 kilns
and lots of other stuff in the water. But my main
studio is still high and dry and I don't trust putting
my goods in the flood zone any longer.
Hematite is anhydrous (without water) ferrous oxide
and yields pigments reddish in color. Limonite is
hydrous (contains water) ferric oxide. It yields
pigments that range from light yellow to dark brown in
color. Ochres, siennas and umbers are from limonite
ores. Ochre is clay permeated with hydrous iron oxide.
The amount of iron present determines whether the
color is yellowish, orangish or reddish brown. Sienna
is ochre with a high iron oxide content. Unlike yellow
ochres, which generally are opaque, siennas are more
translucent. When a limonite, like sienna, is calcined
(roasted) at high temperatures, its water content
(hydration) is eliminated and it becomes a hematite
(anhydrous), like burnt sienna. Umber is iron oxide
shaded with manganese ores. Umbers with the highest
tinting strength are those with the highest content of
manganese and iron. Calcination yields burnt umber,
converting the raw umber limonite to a red hematite.
Should anyone have a lead on sources that have been
consistent in their sales of irons and have been
willing to provide literature with their product,
would you please send me their address so I can obtain
some samples. Please use my email address so we don't
clog the arteries too much on this one issue.
It also dawned on me that I lost my Hamer Book in the
flood since it was in my truck at the time. That was a
major loss to me and now I will have to eventually
replace that as well or go crazy thinking of the
wonderful information it held for me.
William Edwards
=====
http://www.tallapoosariverpottery.com/
Bill Edwards
PO Box 267
Lafayette, AL, 36862
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