Hanington: The science of modeling clay — and Play-Doh

In third grade, our art teacher gave every student a stick of gray modeling clay to make a "lithograph" plate with — you press a flat square piece, engrave the smooth side, rub on a layer of paint and print as many reproductions as you want.

It was somewhat equivalent to linoleum block printing, but didn't need sharp tools to carve. That was my first time using the malleable clay, and I use it to this day when I want to take a photo of a product for AHV to put online — the clay props up the object ideally. Positioning something round under the microscope to get a picture for a report is a snap when you set it in position with modeling clay.

I usually buy the plasticine clay at the Utrecht store at 1025 E. 2100 South, Salt Lake City, whenever I travel there because we use the material at AHV to not only to prop things up but to hold high voltage wires and large components down for temporary bread-board circuits. We used to use Duct-Seal because it was cheap but found out the hard way it was electrically conductive to high voltage arcs and could catch on fire.

Plasticine was invented in 1897 by William Harbutt of Bathampton, England. Harbutt, an art teacher in Bath, England, formulated the non-drying clay for his sculpture students. He created a non-toxic, sterile, soft and malleable material containing approximately 65% gypsum, 10% petroleum jelly, 5% lime, 10% lanolin and 10% stearic acid. It is rather ridged when first used but softens somewhat after time is spent working it. Phycisists classify clay as a non-Newtonian fluid because it does not follow Newton's law of viscosity — that is, it has viscosity that varies dependent on the stress applied.

Before plasticine came along, ordinary clay material dug from ground deposits, was naturally water-based and artists found it very difficult to work with because it just dried too fast. The new material, plasticine, was made from hydrocarbons and clay-like minerals, allowing the item being created to be set aside in a dry environment for long periods without drying out. Of course, items made from the oil-based clay cannot be fired and thus are not really ceramics. But they do serve as an artist's medium because they can be worked in very fine detail. Because of this, oil-based clays are also suitable for the creation of large detailed objects from which sturdy molds can be made. Examples of this include designing life-size prototypes of such diverse objects as automobiles or boat hulls.

Harbutt received a patent in 1899 and commercial production started at his factory in Bathampton in 1900. The original plasticine was gray, but four colors were added later. The original plasticine factory was destroyed by fire in 1963 and replaced by a modern factory building. The Harbutt company produced plasticine in Bathampton until 1983, when production was moved to Thailand.

After World War II, another clay-like product made its appearance as an art medium for children. What we now call Play-Doh was originally first manufactured in Cincinnati by the Kutol Co. as a scrubbing cleaner in the 1930s at the request of Kroger Grocery, which wanted a product that could clean coal residue from wallpaper.

With the diminished use of coal heating after the war, sales of the rubbery material dropped, leaving the owners of Kutol scrambling to find another use for their product. According to legend, Joe McVicker, nephew of the owner, joined Kutol and had some thoughts on what to do, seeing a newspaper from a teacher about making art projects with the wallpaper cleaning putty. They eventually came up with the name Play-Doh after discarding the longer "Rainbow Modeling Compound."

Play-Doh was then marketed to Cincinnati schools in the mid-1950s, with the result that prominent department stores gobbled it up starting in 1956. s promoting Play-Doh aired on influential children's television, such as Captain Kangaroo and Romper Room, starting in 1957. In 1958, Play-Doh's sales reached nearly $3 million. By 1965, General Mills bought the Play-Doh producer.

Play-Doh's current manufacturer, Hasbro, says the compound is primarily a mixture of water, salt and flour, while its 2004 United States patent indicates it is composed of water, a starch-based binder, a retrogradation inhibitor, salt, lubricant, surfactant, preservative, hardener, humectant, fragrance and color. A petroleum additive gives the compound a smooth feel, and borax prevents mold from developing.

More than 2 billion cans of Play-Doh were sold between 1955 and 2005.