Summary: Pigments with the same Color Index name but appearing to be a different hue is confusing for the consumer. Abiding by the Color Index name seems to triumph over the simple visual evaluation of identifying a hue. Part 2 explores the many uses of cadmium, aside from being a pigment, and how it has an impact on the environment we all share.
Cadmium-based pigments are ideal to use when opacity and high heat situations are required. Cadmium is born of a lengthy processing method that relies on acid and heat to yield this important metal. Given both the time and energy involved in the production of cadmium, the high cost of this pigment is not surprising. Cadmium is used to modify other metals to make them easier to solder, to impart strength, to provide nuclear shielding, electroplating, corrosion resistance, a part in cathode-ray tubes, a substrate for semiconductors, and lest we forget, the subject of this article, pigments for a wide variety of applications.
Cadmium pigments have so many useful properties. How many other pigments can be used to color plastics with a very small percentage of colorant, withstand temperatures of over 3,000 degrees C., and remain bright and colorfast throughout their useful lives?
In artist pigments, cadmium is combined with other elements to make cadmium sulfide, cadmium zinc sulfide, and cadmium selenide to obtain a range of colors that starts with a cool yellow, moves to warm yellow, and orange, and ends in a light, medium and dark red. (Note: Some manufacturers employ even darker hues of cadmium that appear maroon or somewhat purple. Grumbacher produced a color called Cadmium Black in acrylics years ago. Cadmium Green does not count. It is a mixed yellow-green color.) The broad range is all accomplished with manipulation of the number of additives and the processing of the ingredients. Cadmium lithopone pigments came later in the pigment manufacturing process. However, the addition of barium sulfate is part of the co-precipitation method not just to bulk the finished cadmium pigment with an extender. However, some artists find cadmium lithopone pigments lack the intensity that is found in cadmium sulfide colorants.
This kind of super pigment status is bound to have a negative side. Cadmium as a metal is highly toxic. However, in most applications around a typical home, cadmium is bound to other chemicals or substrates and is not available to contaminate the user. Many art websites contain the plea of concerned artists/parents who have eliminated cadmium paints from their palette and substituted “safer” ones. Cadmium does not enter the body via undamaged skin so even if one has horrible studio and cleanup practices, cadmium should not enter by skin contact. Using cadmium pigments with spray equipment is strictly forbidden. As with any spray method, the paint gets deposited into the air, and spent material that does not adhere to the targeted spray area falls as a fine dust that creates an inhalation hazard.
Make no mistake in interpreting what I am writing. Cadmium pigments and ALL other colors need to be used with proper care. They are chemicals that demand our understanding and safe handling. Using good studio practices, artists can avoid harming themselves and still employ all the available colors. However, we can choose to eliminate some of the most harmful pigments for peace of mind and especially in situations where children or pets could easily encounter cadmium or other pigments and be contaminated by them.
The toxicology community that deals with art materials have indicated that when handled safely, cadmium does not pose a threat to an artist’s health. Cadmium does not exude fumes, nor does it stealthily find other easy paths (skin, eyes, nose, etc.) unbeknown to us when using the pigment that can contaminate our bodies. I still fully understand why some artists are abandoning the pigment. We all want to be comfortable with the materials we are using. I just want to be clear that for those who use cadmium pigments or any other pigments for that matter in a responsible way, the materials do not assure that we will create a hazardous situation in our studio space. The reason I would refrain from using a pigment is more out of a concern that I have to be extra extremely careful handling and disposing of waste or that I might inadvertently contaminate my work area. I prefer to focus on making art rather than learn and practice all sorts of special cleanup measures when dealing with moderate to highly toxic materials.
As I have stated and written about repeatedly, the focus and efforts we put into studio safety should be on the use of solvents that do find stealthy pathways into our bodies and have cumulative effects on us.
The vigilant artist who has eliminated cadmium from their paint box, satisfied that their household is safe from cadmium contamination, unfortunately, has not eliminated two major sources of potential cadmium intake; their household refrigerator and the nearest open window. Unless you live next to a zinc mine, smelting operation, or a plant that performs lots of soldering, all of us are most likely taking in cadmium by ingesting it in the foods we eat, the water we drink, and the air we breathe. Cadmium likes to bind itself in the soil and is absorbed by plants and animals that eat vegetation grown in the soil. Nearly all foods contain some trace amounts of cadmium. However, it is found in higher concentrations in leafy vegetables, potatoes, shellfish, and mammalian filter organs. (kidney and liver) According to the Agency for Toxic Substances and, Disease Registry, the average person takes in about 30 micrograms of cadmium from food per day and the body absorbs only about 1 to 3 micrograms of that 30-microgram input. Air and water vary in cadmium content by location. Smoking provides an added dose of cadmium.
Cadmium is a regular part of the fabric of modern living. Of all the cadmium produced industrially, only 11 percent of it goes toward pigment manufacturing. Eighty percent is used in nickel-cadmium battery production. Cadmium released into the air from burning coal, mining, fertilizers, and other sources influences human health around the globe. The effects of high levels of cadmium contamination on the human body can range from nausea, vomiting, and headaches and may eventually lead to kidney disease, joint inflammation, high blood pressure, and cancer.
One of the most publicized cases of cadmium poisoning occurred in Japan in the 1970s. Citizens of a particular area had their water supply contaminated by the waste products of a zinc refining plant. Drinking the water caused the citizens a great deal of bone and joint pain and was called itai-itai by the local population. This translates to “ouch-ouch” disease and sadly downplays the horrendous seriousness of the toxic effects of cadmium ingestion.
Returning to the issue of Cadmium Yellow Deep, given the Chemical Index Name, it will never likely be relabeled as Cadmium Orange Light. Further, looking back at artists who describe the colors on their palette, I have never come across anyone who reserves a place for Cadmium Yellow Deep. Their workhorse warm yellow is usually Cadmium Yellow Light or Medium and their cool yellow is Cadmium Lemon. (One of the rare instances when food names are linked to pigment names.)
I think I have covered cadmium pretty much from soup to nuts, both of which probably contain some trace amount of cadmium in them. Years ago, while on a trip to London, at a suggestion of a colleague, I dined at a restaurant named – Rules. The restaurant opened for business in 1798 making it the oldest dining establishment in London. I was intrigued while sitting at a table in Rules that it opened a year after John Adams was inaugurated as the second president of the United States. When ordering my meal, I was encouraged to try traditional English food, so I requested the Steak and Kidney Pie. Not only was I getting a trace amount of cadmium from the kidney meat, the concoction tasted like it had been ordered but had been left inadvertently in a food warmer since the restaurant opened in 1798.
Previously Published in
Grammar of Color
Volume 4, No. 1