LEAD IN BRITANNIA METAL FITTINGS
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
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.
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,
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.
Photo: The starboard running light on this model of a United States
Coast Guard vessel is all but unrecognizable with lead "sickness or
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.
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.