Metalworking

METALWORKING

Raw Materials

Mining for gold, silver and other metals is a leading source of toxic pollution. Mining companies often extract vast quantities of dirt and rock and then spray it with cyanide or other chemicals to leach out microscopic amounts of metal.The greatest problem comes from digging the hole, which often exposes sulfur to air and water. The result is a chemical reaction that produces acid runoff that can run out of mines indefinitely. As it goes, the acid leaches heavy metals out of rock such as lead and arsenic and can pollute water supplies.

Responsibly-mined metal is available. However, sometime claims of “green-gold” may not be accurate, so check with Earthworks or other mining watchdog organizations before making a purchase.

Environmental Hazards in the Studio or Shop

Metalworking creates an especially hazardous working environment. Chemicals and byproducts of the metalworking processes are very dangerous—if not controlled and monitored, they can be lethal.

Exposure routes
The main exposure routes for chemicals are by breathing them in (inhalation), eating and drinking materials (ingestion)-which can also happen when large particles are breathed in, brought into the throat by lung clearing mechanisms and swallowed, and by touching things (absorption). Do not eat or drink in the workshop.

Smoking
Smoking seems to react synergistically with many chemicals and dusts metal workers have been exposed to, in some cases multiplying the risk of damage dramatically-don’t smoke.

Ventilation
Consensus amongst metal workers says that studio ventilation is incredibly important. Dilution ventilation is simple— it is created by the passage of air through an open window, into the studio, and out another shop window. Although inexpensive, dilution ventilation is generally not an effective approach. The preferred ventilating method is local ventilation, which means a sucking device, slot or tube, close to the working area that is generating the dust, mist or fumes that need to be vented. A fume hood is a good example. Remember that the illusion of safety can induce one to do more dangerous things than one should. Fume hoods should be tested every time you use them with a smoke trail or soap bubbles.

Dusts
Employ the least dust producing techniques and processes possible. If possible, work wet so that particles cannot become dust in the air. Wet belt sanders are available for working metals (and other materials) and do a great job. They run cold so one can hold a piece onto them without it heating up in one’s fingers.  The sanders also keep a lot of dust out of the air. When working with silicon carbide separating discs you can use a wax lubricant which binds most dust generated into a paste and keeps it out of the air.

One of the big sources of hazardous dust is investing for casting. Investment contains 40-50% cristobolite, a form of quartz which is many times more likely to cause silicosis than standard quartz does. It is therefore very important to be careful when mixing investment, quenching a flask and removing investment. Local ventilation sucking from where you are working is necessary.

Dust collectors
Sometimes metal workers use dust collection systems intended for wood working on their polishing machines. This is fine as long as metalworking is not mixed with woodworking under the same dust collection vacuum. Hoses containing saw dust can easily ignite with sparks from metalworking or hot pieces of metal filings.

Fumes
Fumes are small particles of a material, often from metals that have been melted. These may be very tiny and can be breathed into the lungs. Metal fume fever is a real hazard with molten metals. It has numerous names, the nastiest of which is ‘the smothers’.  Metal fume fever can be caused by zinc, copper, magnesium, aluminum, copper, antimony, cadmium, iron, silver. The particles are so small (0.01-0/5 microns) that they stay in the air a long time. Casting brass is a particular culprit, often because ventilation is frequently a hood type above a casting machine and the fumes are then drawn past the worker’s face on their way out.

Handling gases
Always regularly maintain and check torch connections and hoses. Test all connections for leaks every time you change a gas in the system. Avoid oils on gas fittings (which can spontaneously combust from oxygen), keep cylinders chained up, and never twist a main valve more than 1/4 turn, so it can be turned off quickly in an emergency.

Metals
Exposure to multiple metals can result in interactions between them, which result in greater damage to health than exposure to a single metal alone. For example, the interaction of cadmium and zinc, or the ability of lead to displace calcium (a metal), which affects the nervous system. The worst metals to have around include cadmium, nickel, antimony, beryllium.

Nickel
Nickel fumes are a proven carcinogen. No amount of exposure to carcinogens is safe. Although in many parts of the world it is still normal for jewelers to alloy their own nickel white gold with a commercially supplied pre-alloy containing nickel, this practice is unsafe. As well as being a carcinogen in the form of fumes from the melt (and reticulation), nickel is proven as one of the most potent of skin sensitizers. Contact with it or its salts can cause various kinds of dermatitis and make one more susceptible to developing allergies to other metals. It dusts and filings are also hazardous. Nickel salts are commonly used in electroplating.

Avoid solvents
Do not use solvents unless absolutely necessary. Organize work processes to avoid solvent use. The kinds of solvents found in workshops have become less unpleasant than in the past. Xylene, tri-chloroethylene, methylene chloride, butyl acetate and many other toxic solvents used to be common fare in the metal worker studio. Try not to use procedures that require the use of solvents.

Benzene should be a banned substance. It is banned from many university labs as too toxic and greatly carcinogenic, also causing anemia and attacking the bone marrow. If the use of solvents is necessary, use less harmful methods first. Abrasive scrubbing can sometimes work. Then try a vegetable oil (if removing grease), then paint thinner, isopropyl alcohol, denatured alcohol, and finally acetone. Gloves and local ventilation should also be used. Use tweezers to pick things up and move them around-just like a photographer uses tongs to keep their fingers out of the chemicals.

Solvent substitution
Use water-soluble materials whenever possible. A successful substitution is a product called ‘Conductor’, an acrylic paint based copper conductivising paint for making non-metals conductive for electroforming. The previous conductivising solutions used butyl acetate and other solvents. Water based polishing compounds help reduce dependence on solvents for degreasing after polishing. Citrus based solvent replacements are useful but there are questions about their long term safety. Other methods of degreasing include steam, carbon dioxide blasting and ultrasonics.

Acids
Metal workers have traditionally used sulfuric, nitric, and hydrochloric acid, as well as mixtures of the last two as aqua regia. All are dangerous to have around. All require splash goggles, gloves, rubber aprons, fume hoods. There is very little need for concentrated acids in most metal or jewelry workshops. Pickles and etchants can be provided by using salts that form dilute acids. Electro-etching allows one to use very diluted acids and even plain salt water to etch many metals, and acid testing of metals can be replaced to a great extent by electronic metal testers. If acids are essential, use proper precautions and a fume hood. Use them diluted, use hardware store acids rather than industrial strength, and treat them with care. Hydrofluoric acid is especially dangerous and is known to cause injury. If at all possible, hydrofluoric acid should be removed from shops and studios.

Children and Pregnancy
Children are particularly susceptible to chemical exposure because of their small body size. It is our recommendation that children not be permitted into metal workshops. Pregnant women should seriously consider leaving the studio for the duration of their term, spending time designing in pencil and other media that is not too toxic. A pregnant woman transfers chemicals easily to the fetus, which is extremely susceptible to toxins. Metal dusts, solvents, other chemicals, metal salts and oxides all have potential to injure the fetus.

Comments

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