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LEAD IN BRITANNIA METAL FITTINGS
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Copyright (c) 1997. All rights reserved. Lead in Britannia Metal Fittings, By Gene Larson The question of whether or not to use
lead or lead-bearing alloys such as britannia
metal in ship model fittings has long been controversial with model
builders. Under certain conditions, something definitely occurs to fittings
that can be traced to their lead content. Whether this
"flowering" of the metal, which can partially or even totally
destruct a fitting, is the result of an electrolytic or chemical or other
action is still to be determined. However, purchasers of fittings, either
in kits or individually, should be aware that there is considerable
latitude applied to the definitions of "lead free" and "britannia." I thought it would be interesting to
compare what several people in the ship model fittings business might say
about what "lead-free" and "britannia"
mean. These comments report the results of telephone inquiries. Photo: Notice the characteristic
tell-tale white powder on anchor and on the deck beneath the stock on this
model of a French fishing boat. Courtesy Old My
interest began during a conversation with William J. Lewis, president of
Boucher Ship Models which recently closed its doors in Dana
Wegner, curator of ship models for the United States Navy, told me that
modelers in his shop use R-8 from Ney Products.
This material contains tin, antimony, copper, and essentially no lead;
R-8's lead content should be no greater than 0.05 percent. Wegner reported
that R-8has held up well even under the extreme conditions some of their
models encounter in various displays around the world. Specifications
provided to contractors who are building ship models for the United States
Navy state that "lead or lead-bearing compounds are not suitable for
any component" of a model. When
Model Shipways was owned by John Shedd in Bogota, New Jersey, they cast their own kit fittings in
a white-metal material which had a high lead content; I witnessed John
dumping old, nearly 100-percent lead automobile tire weights into his
molten casting material. Model Shipways was acquired by Model Expo,
recently of The
last leading American kit manufacturer I contacted was Robert L. Hammer at BlueJacket Shipcrafters in When
asked, Ron Mayer, at Ney Products, explained that
their D-1casting metal in fact does contain 4 percent lead. He claims lead
eases the casting process since it helps the alloy pour better. He told me
that britannia typically contains 92 percent tin
and 8 percent antimony, but that it is impossible to remove all traces of
lead. I asked if it was all right to call D-1 britannia, and he
hesitatingly said yes, but added that it may not be called lead-free. Mayer
asserted that there has not been a problem with D-1 as long as it was kept
out of corrosive environments much stronger than those found in ship model
display conditions. From an environmental view, Mayer added, D-1's
4-percentlead content causes no inhalation problems, but ingestion should
be carefully avoided! Mayer
provided a little background on britannia.
Historically, britannia pewter, or Cornish tin, contained
1 to 2 percent lead. The tin was naturally high in lead content and the britannia product historically was never lead-free.
Currently, "lead-free" means less than0.2 percent lead, and the
United States Food and Drug Administration requires that eating utensils
contain less than 0.01 percent lead. Mayer added that britannia,
nowadays, is considered to have less than 0.05percent lead.
The
weight of metal fittings in a given ship model kit is relatively small, and
the increased cost to provide low- or nearly lead-free fittings is well
worth the investment to insure that the parts will remain stable. However,
some manufacturers have commented negatively on the high price of D-1 britannia metal for fittings. In addition, some have
commented that it can only be cast a limited number of times before it
becomes unworkable to the point that waste cannot be continuously returned
to the pot to save cost. Both Hammer and Mayer say this is not a problem if
some virgin material is consistently added to the melting pot, but this
adds to cost.
D-1
britannia metal with its 4-percent lead content
is far more stable than some white metal fittings currently being marketed.
I have worked with English kits, for example, whose numerous fittings
contain as much as 52 percent lead. The manufacturers state they have received
no complaints about degradation of their components. A possible explanation
for this is that most English kits produce large models which are intended
for radio control which are not usually cased. It has been suggested that
lead-bearing fittings on ship models displayed in cases are more prone to
degrade than those on uncased models. Advertisements
that say "lead free" or "britannia"
may not always be totally correct. The best approach is to carefully
question the manufacturer of cast fittings regarding their lead content -
then make your own decision. ---------------------------
Additional
Thoughts, by Joe McCleary Pewter may or
may not have lead in it depending on how old it is. Modern pewter must be
lead free because it can be used to make eating and drinking vessels. But
other than being lead free, modern pewter can contain anywhere from 85 to
96 percent tin, with the remaining ingredients being copper, bismuth, and
antimony. Webster defines pewter as being any of various alloys having tin as
the chief component. My Mechanics Handbook (1904) defines britannia metal as being fifty parts antimony,
twenty-five parts tin, and twenty-five parts bismuth. Charles
Hull, in Pewter (United Kingdom: Shire Publications Ltd., 1992)says that
the Worshipful Company of Pewterers, starting in
the sixteenth century, authorized three grades of pewter: Fine, for eating
ware, with96 percent tin, and 4 percent copper; Trifle, also for eating and
drinking utensils but duller in appearance, with essentially 92 percent
tin, 4 percent copper, and up to 4 percent lead; and Lay or Ley metal, not for eating or drinking utensils, which
could contain up to 15percent lead. I
started using printers' type metal for casting ship model parts thirty-five
years ago. Type metal also has a variably defined composition but is
generally 50 percent lead, 40 percent tin, and 10percent antimony. The lead
was a cheap base metal, tin made it harder and
kept it from corroding. The antimony made it even harder and helped to make
better castings because it expands as it cools and thus keeps castings from
shrinking in their molds. In some of my earliest models, I used my
type-metal castings alongside purchased white-metal fittings. The
type-metal fittings did not corrode while the white-metal fittings nearby
did. Some of my oldest type-metal castings still look as good as the day
they were poured. About
ten years ago, I switched from type metal to lead-free pewter, not for the
metal's durability, but so I would not poison myself as I worked. As
off-set and xerographic printing techniques replaced traditional methods,
it became hard to find print shops willing to sell worn and broken type. A
low percentage of lead has no effect on durability. In fact, I think it
makes for easier and better casting due to the "wetting and
flowing" properties of lead, which is why it was and is used in some
solders. As a bottom line, I offer four cautions. First, beware of a product name because it can represent whatever its seller wants; make him define his wares. Second, a low percentage of lead, less than 10percent, and a high percentage of tin, not less than 80 percent, will produce durable castings but users should beware of inhaling, absorbing, and ingesting fumes and filings. Third, use lead-free products if you are concerned about health and understand they are a little, but not much, harder to cast. Fourth, a small percentage of antimony will make better castings because of its hardening and mold-filling properties. |
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