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more red clay stuff



Hi all.  Hope you find the following useful.  There are several ceramic
supply houses with web sites.  If you have any trouble locating one, let me
know.

The red coloration in red clays is produced by ferric oxide.  In nearly 40
years of working with ceramics, Iíve not heard of any naturally occurring
red clay other than ferric oxide.  Red is very difficult to produce in
ceramic art using any other element other than iron.  There have been reds
of bright hue produced recently but these are less stable elements such as
selenium encased in zirconium; something not found in nature.  The red clay
(or red art clay) available at ceramic supply houses for around $8 per 50lb
bag contains 6% to 8% ferric oxide.

Now whether this is what the plants need or not, I am going to have to
leave to the biologist in the group.  I am an engineer and most of the
botany associated with plants is still a mystery to me.  So if the ferric
oxide is OK with the plants, it can also be purchased at a ceramic supply;
about $15 for a 50lb bag.  This can be added to any clay to increase the
iron content.  Chelated iron is also readily available at garden stores in
my area and mixed with the clay to improve the substrate.

My potters dictionary says laterite is a hydrated form of alumina, silica
and ferric oxide.  A specific type of laterite containing more than 50%
alumina is bauxite.  Since the largest concentration of bauxite in North
America is west central Arkansas (near Hot Springs), it is probable the red
clay I grew up around is laterite.

A useful clay referred to recently in the group is bentonite.  This clay is
used in small quantities to "flock" clays and slips (a watery clay that is
used in casting).  It is very "sticky" when wet due to itís electrically
charged molecules.  Add it to the balls you make to put in the substrate
and they wonít fall apart on you when you put them in the tank.

Finally, let me recommend "Ironite" for the substrate. It is a micro
nutrient material (mostly insoluble) with 4.6% ferric sulfate.  I found
this in the local garden centers while I was looking for the micro nutrient
mix for PMDD and Iíve read several references to it by members during the
past year.  It worked reasonably well as a substitute for the micro
nutrient mix in PMDD but I had no idea how to accurately dose it so I
discontinued its use after I obtained Plantex but it should work well in
the substrate.

I hope you find this information useful and by the way, the ceramic supply
houses sell in small quantities (1lb) although the price is higher; e.g. $1
a pound for ferric oxide in small quantities.

Regards,
Onis
k5vkq at ix_netcom.com