Janet Kaiser on wed 21 may 03
For anyone in the UK who is concerned about lead (and/or cadmium) and
possible "leaching" from a glaze or more correctly "metal release", they
should ask for proof the ware has been tested and found to meet British
Standard BS6748. Lead and cadmium are the only two which are required to be
tested.
There used to be a rule-of-thumb test that potters using lead-based glazes
could try on each kiln load, sparing the expense of laboratory testing more
than absolutely necessary. I do not remember the exact method, but it used
white vinegar and a potassium sulfide? or sulfate? mix for comparison. Not
a lemon in sight!
Some local councils do spot-checks on the work of production potters,
irrespective of what ingredients the maker claims are or are not in the
glaze and/or the decoration. A pot is bought (often anonymously, without
divulging who the buyer is or for what purpose) and subjected to testing.
Testing uses hydrochloric acid (see below) and takes a couple of weeks. A
certificate is issued for that pot, much as a M.O.T. is issued on a car...
In other words, the car was technically sound and road-worthy the day it
was tested, but the testing body cannot be responsible for subsequent days.
The council can take punitive action against any potter found to be in
breach of any of the numerous codes of practice and certainly if they are
found to be producing work which does not meet the above British Standard.
I expect there are European standards in the pipeline, but I do not know
what... They are still sorting out more important issues like the
definition of an "island"! (No, don't ask :-)
Anyway, it is local government which is responsible for seeing the
manufacturing regulations are being adhered to. The Trading Standard
Authority can become involved if retailed work poses any threat or danger
to customers. Only one of many reasons why reputable retailers ask potters
for a clear statement about the glazes they use and usually require they
include a written statement to that effect when they sign their consignment
agreement. If either lead or cadmium are used, the gallery will require
proof of BS certification. They will/should also ask for regular updates
which proves the maker is keeping on the ball...
The only exception is work that could never be used for culinary use...
Now, even a potty could, in theory be used to serve mulled wine or citrus
summer cup and a platter which has been made to hang on the wall for purely
decorative purposes could be taken down to serve viands garnished with
juicy orange and lemon slices... Even some "non-functional" teapots could
in theory be used to serve tea and a wall tile could be used as a cutting
or serving surface, but there has to be some common sense left in this
world! As Janet Hamer commented when she signed her consignment
agreement... "Even if someone sucks hard on my bird sculptures, the risk of
lead poisoning is non-existent".
Of course only lead fritts are permitted in commercial manufacturing
situations. A potter could in theory use raw lead, but his employees may
not. But I doubt very much that anything other than lead monosillicate,
lead bisillicate or lead sesquillicate are obtainable even for the most
life-weary potter... Even then, lead monosillicate does not meet British
Standards or regulations covering lead in glazes as it is too "soft". A
glaze has to have less than 1% lead content to qualify as "lead free" in
the UK so I guess that those using some untested glass cullet would
probably not conform with this standard.
Lead oxides are soluble in the bloodstream and like all heavy metals are
considered "culminative poisons". In other words, the body cannot rid
itself of any lead which enters the system. The use of raw lead is
generally banned by law in the UK but there are exceptions which are
tightly controlled by licensing through the Health & Safety executive.
Fritted lead silicates are simply powdered glass which have been
manufactured to certain standards and are certified as "low solubility" and
labelled low sol. or LS... This means that not more than 5% may dissolve in
the hydrochloric acid test mentioned above. I believe certain other oxides
can affect these properties in lead glazes (aka leaching) by increasing or
diminishing the solubility of the lead. For example, I seem to remember
copper was avoided, so it must increase solubility..?
So much for the finished ware. As for the dangers to the maker... Everyone
using these glazes should be well educated and knowledgeable about all the
potential hazards. They must implement all the basic health and safety
precautions necessary when using potentially hazardous materials in their
raw state... Masks when mixing, not exposing skin by hand-mixing, dipping,
etc. etc.
But however stable the glaze or safe the product is once fired, lead is
volatile at high temperatures, so kilns must be well ventilated and the
potter should never inhale fumes from the kiln. Even opening a kiln door
whilst the ware is still hot is considered unsafe practice and any pots
with lead-free glazes in the same kiln will be deposited with a thin lead
"skin", rendering them dangerous to use even if the lead-glazed are OK. I
do not remember the reason why, but firing lead glazes in electric kilns
has always been considered unsafe practice. The more technically minded
could perhaps explain why, although it is probably in the archives
somewhere.
Just for the record (again), I *personally* believe that a lot of
hysterical paranoia arises from the very word "lead" these days. It has
become a buzz word which will trigger a lot of ill-informed angst and
horror. Media hype and urban legend horror stories fuel the fire. Yes,
cheap travel means that lead-glazed ware which one can buy in countries
without controls can be considered dangerous. But in countries where
testing and safety rules have been in place for many years, we also have a
lot of very irresponsible people to blame for there being this perceived
problem. Some of the sloppy practices employed in the past -- whether
through ignorance or sheer bravado -- have resulted in all forms of lead
becoming an absolute no-no. On the whole, this is probably a Good Thing to
have happened, because where there is a potential hazard or danger it is
best to keep it out of general circulation, so it does not and cannot fall
into ignorant, unskilled or uncaring hands like the potter May Luk refers
to firing without a kiln vent in a working space.
However, why should the lowest common denominator be dictating our whole
attitude towards lead? Legislating to make something "idiot proof" so we
are in the absurd situation, whereby it is OK for industry to continue
using lead-based glazes, but not the responsible studio potter. But like I
say... The price is being paid for irresponsible individuals and companies,
plus the new breed of litigation lawyers with the support of public safety
and hygiene "experts" who pray on "weaknesses in the system". Lead is such
an easy target, which is just too bad IMHO.
Sincerely
Janet Kaiser
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