Modelling clay

Modelling clay is any of a group of malleable substances used in building and sculpting. The material compositions and production processes vary considerably.

Ceramic clay

Ceramic clays are water-based substances made from clay minerals mixed with other raw materials. They are baked at high temperatures, in a process known as firing to create ceramics, such as terra cotta, earthenware, stoneware, and porcelain. Paper clay produced by pottery clay manufacturers is any of these clay bodies, to which a small percentage of processed cellulose fiber has been added. When kiln fired, the paper burns out, leaving the clay body. Consequently the firing temperatures and glazes selection should be the same on those used with the clay body.

Oil-based clay

Oil-based clays are made from various combinations of oils, waxes, and clay minerals. Because the oils do not evaporate as does water, oil-based clays remain malleable even when left for long periods in dry environments. Articles made from oil-based clays cannot be fired, and therefore are not ceramics. Because the viscosity of oils decreases as temperature rises, the malleability is influenced by heating or cooling the clay. Oil-based clay is not soluble in water. It can be re-used and so is a popular material for animation artists who need to bend and move their models. It is available in a multitude of colours and is non-toxic.

Ice cream

Ice cream (derived from earlier iced cream or cream ice) is a sweetened frozen food typically eaten as a snack or dessert. It is usually made from dairy products, such as milk and cream, and often combined with fruits or other ingredients and flavours. It is typically sweetened with sucrose, corn syrup, cane sugar, beet sugar, and/or other sweeteners. Typically, flavourings and colourings are added in addition to stabilizers. The mixture is stirred to incorporate air spaces and cooled below the freezing point of water to prevent detectable ice crystals from forming. The result is a smooth, semi-solid foam that is solid at very low temperatures (<35 °F / 2 °C). It becomes more malleable as its temperature increases.

The meaning of the phrase "ice cream" varies from one country to another. Phrases such as "frozen custard", "frozen yogurt", "sorbet", "gelato" and others are used to distinguish different varieties and styles. In some countries, such as the United States, the phrase "ice cream" applies only to a specific variety, and most governments regulate the commercial use of the various terms according to the relative quantities of the main ingredients, notably the amount of cream. Products that do not meet the criteria to be called ice cream are labelled "frozen dairy dessert" instead. In other countries, such as Italy and Argentina, one word is used for all variants. Analogues made from dairy alternatives, such as goat's or sheep's milk, or milk substitutes (e.g., soy milk or tofu), are available for those who are lactose intolerant, allergic to dairy protein, or vegan.

Play-Doh

Play-Doh is a modeling compound used by young children for art and craft projects at home and in school. Composed of flour, water, salt, boric acid, and mineral oil, the product was first manufactured in Cincinnati, Ohio, U.S., as a wallpaper cleaner in the 1930s. When a classroom of children began using the wallpaper cleaner as a modeling compound, the product was reworked and marketed to Cincinnati schools in the mid-1950s. Play-Doh was demonstrated at an educational convention in 1956 and prominent department stores opened retail accounts. Advertisements promoting Play-Doh on influential children's television shows in 1957 furthered the product's sales. Since its launch on the toy market in the mid-1950s, Play-Doh has generated a considerable amount of ancillary merchandise such as The Fun Factory. In 2003, the Toy Industry Association named Play-Doh in its "Century of Toys List".

History

Origin

The non-toxic, non-staining, reusable modeling compound that came to be known as "Play-Doh" was originally named Rainbow Modeling Compound. It was a pliable, putty-like substance concocted by Noah McVicker of Cincinnati-based soap manufacturer Kutol Products; it was devised at the request of Kroger Grocery, which wanted a product that could clean coal residue from wallpaper. Following World War II, with the transition from coal-based home heating to natural gas and the resulting decrease in internal soot, and the introduction of washable vinyl-based wallpaper, the market for wallpaper cleaning putty decreased substantially. McVicker's nephew, Joe McVicker, joined Kutol with the remit to save the company from bankruptcy; he subsequently discovered that the wallpaper cleaner was being used by nursery school children to make Christmas ornaments.

Clay

Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Clays are plastic due to their water content and become hard, brittle and non–plastic upon drying or firing. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Depending on the content of the soil, clay can appear in various colours, from white to dull gray or brown to a deep orange-red.

Clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties, and many naturally occurring deposits include both silts and clay. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm.Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger.

Liberty Bell

The Liberty Bell is an iconic symbol of American independence, located in Philadelphia, Pennsylvania. Formerly placed in the steeple of the Pennsylvania State House (now renamed Independence Hall), the bell today is located in the Liberty Bell Center in Independence National Historical Park. The bell was commissioned from the London firm of Lester and Pack (today the Whitechapel Bell Foundry) in 1752, and was cast with the lettering "Proclaim LIBERTY throughout all the land unto all the inhabitants thereof," a Biblical reference from the Book of Leviticus (25:10). The bell first cracked when rung after its arrival in Philadelphia, and was twice recast by local workmen John Pass and John Stow, whose last names appear on the bell. In its early years, the Liberty Bell was used to summon lawmakers to legislative sessions and to alert citizens to public meetings and proclamations.

No immediate announcement was made of the Second Continental Congress's vote for independence, and thus the bell could not have rung on July 4, 1776, at least not for any reason related to that vote. Bells were rung to mark the reading of the Declaration of Independence on July 8, 1776, and while there is no contemporary account of the Liberty Bell ringing, most historians believe it was one of the bells rung. After American independence was secured, it fell into relative obscurity for some years. In the 1830s, the bell was adopted as a symbol by abolitionist societies, who dubbed it the "Liberty Bell." Similarly suffragists adopted the bell as a symbol, calling it the "justice bell."