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The Use of Chemicals in Horology: Safety issues and available substitutes
by Gordon Bolger, Ph.D, Chapter 187 NAWCC
Introduction
There are numerous applications where chemicals are used in the horology trade. A summary of the most commonly encountered, the risks involved in their use and how one can protect themselves from these risks follows. In addition, there is a section on some available substitutes to commercially available chemicals which are just as effective, cheaper and even safer.
Chemicals and Their Use (Hazards at our fingertips)
Group 1: Organic (containing carbon) Solvents
One of the most common encounters with chemicals in the workshop is with volatile organic solvents used for cleaning (i.e. Degreasing / removing oil) a watch or clock movement. The problem with these solvents is that they can be inhaled or absorbed through the skin. These solvents can take several forms and fall into the category of:
(i) Very dangerous and should not be used at all: Benzene, chloroform, carbon tetrachloride, trichloroethane, ether. The use of these solvents could possibly result in a deadly consequences.
(ii) Dangerous: Perchlorethane, trichloroethane, toluene, methyl isobutyl ketone.
(iii) Acceptable, but handle with care: Acetone, naphtha (benzine), methylene chloride, xylene, turpentine, mineral spirits (Varsol), Stoddard solvent, methyl ethyl ketone and methyl, ethyl and isopropyl alcohols.
Solvents may also be encountered while using various adhesives and paints (i.e. G=S Hypo cement contains xylene, heptane and poly-N-butyl methacrylate)
Group 2: Inorganic (not containing carbon) solvents and solids
Equally as frequently encountered are inorganic solvents (most common is water) and salts.
Inorganic solvents and salts can also be categorized according to the risks that they pose when working with them.
(i) Very dangerous: COULD BE DEADLY AND SHOULD BE USE WITH EXTREME CAUTION or not at all (find substitutes): Potassium or sodium cyanide as solids or solutions (mixing cyanide with acid liberates hydrogen cyanide an extremely poisonous gas), various acids, hydrochloride (fumes in humid air), phosphoric, sulphuric (concentrated or dilute, extremely corrosive), nitric acid and hydrofluoric acid
(ii) Acceptable but use with caution: Cleaning solutions containing ammonium hydroxide in combination with other caustic inorganic agents (i.e. sodium hydroxide or Lye as it is commonly known).
Group 3: Mixtures of organic and inorganic chemicals
(i) Acceptable, but handle with care: Water based cleaners which are a mixture of ammonium hydroxide and surfactants or soaps (Caution: Never mix ammonia based cleaners with bleach (sodium hypochorite), the result is production of hydrazine and chlorine, an extremely dangerous combination)
Group 4: Metals and radionuclides (radioactive substances)
Most metals have a low reactivity and thus pose no problems, but some are to be considered dangerous and handled with caution and include, lead, mercury and arsenic. Radionuclides, such as radium 226, used in dials, are less likely to be encountered. Lower energy emitting radionuclides (i.e. Tritium) in combination with chemical luminescence have replaced the use of radium 226. Heating silver, nickel, copper, cadmium, tin, aluminum and antimony to a temperature above their melting point can cause the metal to vaporize, the vapour being toxic.
Encounters with the more dangerous metals and radionuclides is more likely to occur when working on the restoration of older time pieces.
WHY ARE CHEMICALS HAZARDOUS?
The vast majority of chemicals that are used in horology are not compatible with living systems, that is they do no naturally occur in living organisms. As such, upon exposure at a certain concentration they will kill living cells. In short they are toxic to living entities and considered hazards.
GAINING ACCESS TO THE BODY: HOW HAZARDOUS CHEMICALS ARE A THREAT TO THE USER
Hazardous chemicals can gain access to the body in the following ways:
(i) Inhalation: Via nose and mouth into the lung: This is the preferred route of entry for solvents and particulates such as metal dust and vapours which are absorbed into the blood via the lungs.
(ii) Skin: The skin is the largest organ in the body and is susceptible to absorption of most solvents subsequent to which they can enter the blood and accumulate. Organometal complexes are rapidly absorbed in this manner (i.e. methyl mercury). Particulate substances are repelled by the skin. However if not properly washed away, they can enter the mouth and gain access to the gastrointestinal tract and subsequently the blood.
(iii) Mouth: Transfer from hands to mouth or by putting contaminated objects in the mouth (re: radium 226 and dial painters).
(iv) Exposed mucous membranes: Absorption into the eyes, does not normally lead to appreciable burdens of compound in the blood, but may lead to local irritation in the eye.
CONSEQUENCES
The consequences of hazardous chemicals gaining entry into the body is dependent on where they have entered and the amount of exposure that has occurred upon either a single exposure or repeated exposure. Chemical toxicities usually manifest themselves following single or multiple exposures. The continued use of some chemicals / metals can lead to accumulation and toxicity once a minimum level has been reached in the body.
(i) On skin localized, not absorbed into the blood: Local irritation, allergic reaction (redness, swelling and itching), drying and cracking of the skin (contact dermatitis) can result upon acute or chronic use of chemicals
(ii) On mucous membranes (eyes, lips, mouth, nasal passages, lung): In the eye, can lead to redness, irritation and swelling of the conjunctiva membrane, high exposure can lead to blindness; in the lung can lead to difficulty in breathing and an asthma like reaction; in the mouth, localized irritation can occur. The biggest offenders for mucous membrane irritation solvents.
(iii) Absorbed into the blood: Can lead to both short and long term effects with central nervous system, kidney and liver toxicity the most important; long term exposure can lead to the development of cancer of the blood, bones and a variety of other organs.
ALL OF THE PRECEDING CHEMICALS DISCUSSED CAN CAUSE ON OR MORE OF THESE EFFECTS. THE TOXICITY OF SOME CHEMICALS IS INCREASED WHEN THEY ARE BURNED (i.e. solvents)
In addition to being toxic to the user, some of the preceding mentioned chemicals are also toxic to the environment (i.e. solvents containing chlorine, fluorine or bromine can destroy the ozone layer).
PROTECTION
- Limit the use of hazardous chemicals
- Dress appropriately, wear protection if you can and make it more difficult for hazardous chemicals to gain entry into your body (i.e. goggles, rubber gloves, rubber apron, organic vapour and particle masks)
- Contain hazardous chemicals and limit their ability to gain access into your body (i.e. Wash parts in sealed containers, if possible work in a ventilated hood or provide for adequate ventilation)
- Know what you are working (consult on the Internet, obtain information from the Material Data Safety Sheet which is available from you local health protection branch). If you are not sure of what you are working with, find someone who can properly inform you of the hazards, both short and long term.
SOME SUBSTITUTIONS FOR COMMERCIALLY AVAILABLE CHEMICALS
If possible, look for substitute safer solvents / cleaning solutions (they can be less expensive and may react a little slower, but your health is worth it):
1. For degreasing use “Varsol” or oil based paint thinner, it is excellent as a degreaser for clocks and less volatile than solvents such as trichloroethane. For finer parts, naphtha (lighter fluid) is a good degreaser followed by acetone to get parts squeaky clean (i.e. hair springs, balance wheel, escape pallet and wheel). If you still want to use trichloroethane, use small quantities in a sealed container and open with lots of ventilation (i.e. oven top ventilation hood).
2. Use isothiocyanate or other novel chelating agents instead of cyanide for the removal of copper and silver from gold.
3. For washing bracelets, gold, diamonds and even shining up brass, soak items in a non-ammoniated solution containing a detergent and a complexing agent to chelate metals. A mixture of liquid dish detergent plus a soap scum remover (i.e. Sani Gel®) would work very well.
4. To remove rust quickly, dip in 50% water 50% muriatic acid (concentrated muriatic acid has a tendency to fume, the fumes are dangerous to your eyes, nose and lungs so it is better to dilute it). Once he visual rust is gone, brush the part to remove the loose rust or perform electrolysis if you are set-up to do so. Neutralize the acid in a dilute solution of baking soda and rinse the parts well with tap followed by distilled water and then methyl alcohol. Let the parts air dry or dry with warm air from a hair dryer. If allowable, you may want to treat acid cleaned parts with a silicone lubricant or oil (watch or clock) to prevent the recurrence of rust.
You may substitute vinegar or tea to remove the rust, but they take much longer than muriatic acid.
5. To remove shellac, varnish and some enamels, try using first methyl alcohol, if this doesn't work use acetone. Only use lacquer thinner as a last resort. If possible soak parts in a closed container (for Varsol and methyl alcohol, a plastic container; for acetone and lacquer thinner, a metal or glass container). Do not wipe parts with a rag soaked in the solvent, you will end up breathing all the fumes and creating a fire hazard. Do several dips with fresh solvent to be sure that all the unwanted coating is gone.
All the preceding solvents / cleaning solutions are available in your local grocery or hardware store, this means that they are cheaper than speciality solutions. However this does not mean that they are the best substitutes for the job, try them and make your decision based on experience. These substitutes are also not free of risks so always be careful and follow the package instructions.
THE QUEST FOR EFFECTIVE AND SAFER CHEMICALS FOR USE IN HOROLOGY; AN ISSUE IMPORTANT TO OUR OCCUPATIONAL HEALTH AND SAFETY
Here is what I can do for you if you are interested in additional information on the use of chemicals in the horology workshop:
(i) Provide information to help you understand how novel chemicals or chemical processes work, the suitability of their application and the risks involved with their use.
(ii) Answer questions of a chemical nature, provide information to help make informed decisions.
(iii) Provide up to date information on the potential hazards of chemicals used in the workshop in the form of Material Safety Data Sheet bulletins and inform you where to obtain the appropriate apparel / equipment to safely perform your work.
CONTACT: gordonbolger@gmail.com