Poisons

and

Horological Materials.

By David Bodley-Scott M.B., B.S.,D.R.C.O.G

This page is based on an article by David Bodley-Scott M.B., B.S.,D.R.C.O.G and published in the BHI's Horological Journal in July 1989. In view of it's contents, I have included most of it's text. It is very long but worth reading! Although it was written in 1989, it is still relevant today.

Today we are increasingly aware of pollution and poisons. Whilst others attend to the environment, it is time we looked at our workshops. I am not suggesting that hazards are lurking in every corner, but many materials we handle have over the years been in one poisoning scare or another.

Lead

Few repairers will not have handled lead at some time or another, as a metal it is fairly inactive, but when powdered and breathed in, or converted to a compound and taken in my mouth, it can gradually accumulate in the body as a poison. Red and White leads have been used since Egyptian times and was also used in white painted dials. As a glaze it has been used to coat enamel watch and clock dials, especially in nineteenth century France.

Lead in petrol can also be a problem as some repairers still use petrol to clean oily movements.

Arsenic

The connection between Arsenic and horology is a tenuous one, but many of those repairing bracket clocks have unwittingly handled copper arsenide, the green dye Scheeles Green that was used for dying the silks backing the frets of the bracket clock cases. This dye was popular in the Eighteenth Century for colouring papers and textiles. Poisoning can easily occur if damp encourages mould that can react with the dye to produce Tri-methyl arsine. This is what is supposed to have killed Napoleon.

Mercury

Mercury is another slowly accumulating poison, early signs are headache, lassitude, loss of appetite, indigestion and pallor. Later it can lead to excessive shyness, irritability and mental deterioration. Shakiness makes the hand illegible and the eyes and kidneys are damaged. In horology, we encounter mercury in barometers, compensated pendulums and miniature watch batteries. It has long been used in the dangerous process of Fire Gilding. The Gold was dissolved as an amalgam in mercury, painted onto the base metal of the clock cases and then heated to vaporise the mercury leaving the gold coating the base metal. The air filled with poisonous mercury vapour. Most watch batteries are now Silver oxide, but the older batteries contained mercury. These batteries must be disposed of carefully to ensure that they are not swallowed by children or animals!

Other Metals

A number of other metals can produce a short lived illness called metal fume fever if they are heated to a temperature above their melting point. Silver, Nickel, Zinc, Copper, Cadmium, Tin, Aluminium and Antimony have all produced this disorder. It is not fatal, but the symptoms of nausea, thirst, headache, exhaustion and aching limbs are most unpleasant.

Cyanide

Potassium Cyanide is described as a cleaning agent by most of the older instruction books, though it rejuvenates gilded work a treat, it really has no place in the workshop today. Even in very small quantities it is rapidly fatal. As it is so toxic, it poses problems of disposal and should be inactivated by hydrogen peroxide before being thrown away.

Skin Problems

We have looked at some of the more dramatic effects of familiar substances, I shall now turn to a few that affect the skin.

Nickel is used in alloys for buckles, bracelets, watch cases and cheap costume jewellery, in particular earrings for pierced ears (though in the UK it is now being phased out THS 1996). Perspiration contains salt which can react with the nickel causing severe dermatitis at the point of contact. A tell tale red weeping patch on the wrist points to the recent use of a watch or bracelet made from nickel.

Leather is tanned with Chromium and sweat leaches this out to cause a chrome dermatitis beneath the watch strap.

Ammonia is used by all of us, it can make you choke and your eyes run. If the liquid enters the eyes it can burn and scar the outer coat of the eye, so strong solutions must be handled carefully. Dirty clock parts are often scrubbed in ammonia solutions, if the worker does not wear gloves, he will develop painful cracks in the skin which can take a long time to heal. Any cleaning solvents can remove the protective waxes from the skin and cause sores and cracks which can then easily become infected.

Horologists use a variety of reasonably safe brews in which to clean clock and watch parts, some of these are water based containing ammonia, soap and at times extra solvents such as acetone or oleic acid. The non-water based ones are made up in toluene, white spirit or sometimes xylene. Xylene typically turns into a white deposit if discarded into water, it has been replaced with toluene, or white spirit in most cleaning compounds. Ammonia gas is passed through the solvent to form a saturated solution of ammonia in, for example toluene. Once exposed to the air, ammonia slowly evaporates. Unfortunately the ammonia cannot be replaced in the workshop by simply adding "880" ammonia as this contains water. The only answer is to bubble dry ammonia gas through the spent cleaning solution. The rinses are simply pure solvent in the form of toluene, white spirit, or Xylene, a lubricating rinse contains not oil but a substance that deposits an ultra-thin layer on the parts.

I cannot leave the skin without mentioning Silver as a potential poison. Silver salts are present in the silvering compounds used for clock and barometer dials. Quite rightly, the containers are labelled as poisonous and the salts should not be ingested.

Solvents

Solvents are found in many cleaning solutions throughout many industries. Carbon tetrachloride damages the liver leading to jaundice, liver failure and death. Ether is explosive and inflammable. Benzene ( Benzol in Germany and the USA) can cause leukaemia. To save confusion found in many books, I must emphasise that Benzene is different from Benzine, otherwise known as petroleum ether. Benzene was often used in production of motor fuel, solvent for rubber and the rapidly expanding cellulose industries. It was here that it caused many deaths from poisoning. Acute benzene causes headache, excitation, flushed face, giddiness, incoherent speech, pins and needles leading finally to narcosis and death.

Development of moulded plastics lead to the extensive use of Chlorinated Hydrocarbons - Ethyl Chloride, Tetra-Chloro-Ethane and Carbon Tetrachloride, all of which attack the liver. Recently ICI have developed a modern so called safe Chlorinated Hydrocarbons, Di-Chloro-Methane, Tri-Chloro-Ethylene, Per-Chloro-Ethane, Tri-Chloro-Ethane, and the CFC Tri-Chloro-Fluoro-Ethane, all of which received a good report from the 1984 British Health and Safety Executive. Unfortunately, we are now faced with the toxic effect not on us but on the atmosphere. The CFC's are causing holes in the atmosphere, and are being banned and replacements introduced.

Radioactivity.

When luminous dials and hands became all the rage in the first decade of this century, women dial painters would lick their brushes and rapidly absorbed dangerous quantities of radioactive Radium 226. This compound causes bone cancer. It has been common practice for watch repairers to scrape off old cracked radioactive luminous paint from watch dials and hands and repaint with Tritium which emits less harmful Beta particles. Intact skin is a barrier to Alpha particles, but if the dusts of the old luminous paint is inhaled it enters the body and can be absorbed. Professor Derwent Mercer, recently Chairman of the BHI, advised that if such work is unavoidable, The hands of the watch or clock should be scraped while immersed in oil and the scraper left submerged in the oil to prevent the particles entering the air being breathed.

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