SC - Re: Tudor greenware - Lead poisoning?

[RANDALL DIAMOND]

Meliora wrote:
>>>However I was taught yesterday that lead glazes (which were the usual
means of creating a green glaze) made with raw materials (lead, silica etc.)
were dangerous as the lead leeched out during the glaze firing process.
But, if
the raw glaze elements were fired together first to form a glass and then
ground and added to water and a binder and then used to form the glaze
(process is called frittering), then the tableware would be safe.

Is there any evidence that 15th Century English would know about lead
poisoning, or know how to stop it happening?  I assumed not, as a form of
lead powder was used in face powder in late 16th Century England, but I
thought I should ask anyway.<<<

NINETEENTH century folks mostly didn't have a clue about lead
in ceramics.  Also "greenware" in ceramic terms is unfired clayware;
"Tudor green' ware" is a very limited production technique of ceramic
ware produced, as you say in Surrey, from the late 14th century.
"Frittering" is what I do to wisteria blossoms with a batter and oil;
"fritting" is the accurate potter's term.  I understand how these
terms can be misheard by a beginner.  Among other things, I have
done a bit of ceramic work.  You can see some of  my work in
the December 1992 issue of CERAMICS magazine where they
chose me as "Artisan of the Month".  I (apparently uniquely) paint
copies of Renaissance masterpieces on  plates with underglazes.

Generally the flux (pun intended) over lead in modern ceramics
is very much overblown as far as the dangers, at least the extent
of danger, that is, IMO.   The problem arose with a lot of popular  and
very cheap import ware which had lead overglazes.  These were
definitely dangerous to eat from due to a high, high lead content,
but they really were not made to eat from.  It is a lot like how much
junk you have to stuff in lab rat to give it cancer or how bad and
dangerous asbestos is  (they have admitted they really overplayed
the dangers). The lead oxide (PbO) does not create the green
colour in the glaze, it is the agent that produces the evenness of
the coating of the shiny vitrification of the surface, the "glaze".  It
acts as a fluxing agent.  The colours come from other powdered
minerals mixed in with it.  This is a basic "overglaze" as opposed to
"underglaze" which are pure minerals in a liquid slip, which when fired
have no vitreous sheen.  A clear finish can be added over it in a
second firing.  The importance of glaze is that it seals the porous
nature of plain fired clay (bisque or "biscuit" fired) to moisture; a very
good characteristic for food containers.  It won't "soak up" food tastes
and odors like plain terra cotta clay ware will.  The outgassing of the kiln
for lead glazed pottery is noxious, but generally the other "safe" glazes
are nasty too.  This is akin to the use of mercury to gilt silver.  Just
even
to THINK about doing period giltwork will have the EPA on your back in
a heartbeat!  I know, I am a silversmith too.   You would need a major
chemical laboratory facility to legally do it.   The primary danger of lead
glazes is that they leech out into your food and beverages if you use
these impliments DAILY and can cause health problems.  This is the
same problem that contributed significantly to the deterioration of the
Roman Empire; they were poisoned by their lead water piping to the
extent of severe mental disorders and birth defects.  Modern "food
safe" glazes have absolutely no lead in them and you have been
misinformed that fritting with an overglaze can make them safe.
They can't.  Lead and food are irresolvable.  This is unfortunate,
as the replication of period ceramics really can not be exactly
duplicated in appearance with food safe modern glazes.  I once
made absinthe, growing all the necessary herbs and such for an
entry in A&S.  Period as hell, but also likewise as illegal.  But even
I won't make ceramic food vessels with a lead based glaze.  I have
plenty of lead oxide; it is commonly used in modern NONFOOD art
cermaics like Raku.  Our mundane society is just too litigation happy
to even chance an accurate reproduction being inadvertantly used
and some jerk has his lawyers sue me for everything I have on the
CHANCE that the lead has caused him some harm or might do so
20 years down the line.  That is why I like the SCA; it is more rational
most of the time than "normal" mundane society IMO.

>>>Has anyone looked into this form of pottery?  All extant pieces seem to
be
food related, bowls, cups, goblets and pitchers/jugs with the except of one
incredibly beautiful "bleeding cup".<<<

Oh yes, there is nothing special about it.   It is virtually the same as
ALL the other European ceramics dating from around the 9th
throught the early 14th century, especially ware for the commoners.
Look at the paintings like those of Brugels and you will find many
examples from many European cultures, but most of them are
going to have been manufactured in France or Italy at that time.
The REASON thet you hear specifically of "Tudor green' ware" is
that the state of English pottery making was far, far behind the
French and Italians.   The use of lead glazes over buff ware at
this time in Surrey is the FIRST use in England of glazes since
Roman times.  The reason that so many of the items are food
related is that the  relatively simple process was entirely too
crude to utilize in the growing sophistification of Renaissance
ceramics.  "Art" quality pieces for the nobility were mostly imported
and were in the tin oxide process developed in Italy called "majolica".
Artistic English ceramics largely did not exist until the mid 16th
century with the rise to popularity of a blue glazed ware we know
as "delft".  England became a major producer and exported it
throughout the 17th century until it was replace by pocelain ware.
Also the stuff was made in quite large quantities to satisfy the
demand among the commons; much more was made than the
more costly "artsy" and elegant gaudy stuff for the nobles.
The "Tudor green' ware" was also not restricted to just green.
They also had lead glazed yellows and rich browns.  It did not
last very long as it was surplanted by the spread of majolica
as the secret processes of the Italians spread around Europe
in the 16th century.

Majolica, both period and modern, differs from other glaze
techniques in that the entire piece was coated with a thick
coat of tin oxide, which is a very nice white glaze.  They then
painted the coloured designs on it with very diluted coloured
slip suspensions that would sink INTO the white glaze upon
firing.  This process results in very pastel intensity colours and
is difficult to master.  Too thin an application of colours and it
washes out to nothing; too thick and it will cause bubbles and
pits.  Modern special glazes have been compounded but
they look different from period techiques.

I hope you will enjoy your pursuit of ceramics as much as have
I.   It is a wonderful and useful thing to learn and many nice
reproductions are feasible.  Just use good judgement and
document the period techiques, but explain why you used
modern substitutes in making your items.  If judges have a
problem with this, I hope they have decide to use period lead
based ceramics themselves.  I am a firm believer in "evolution
in action".

Akim Yaroslavich
"No glory comes without pain"