Composition and Toxicology
Shoe polish consists of a waxy colloidal emulsion, a substance composed of a number of partially immiscible liquids and solids mixed together. It is usually made from ingredients including some or all of naphtha, lanolin, turpentine, wax (often Carnauba wax), gum arabic, ethylene glycol, and if required a colourant, such as carbon black or an azo dye (such as aniline yellow). It typically has a specific gravity of 0.8, is negligibly soluble in water, and is made of between 65 and 77% volatile substances—usually naphtha. The high amount of volatile substances means that the shoe polish will dry out and harden after application, while retaining its shine.
Lanolin, a hydrophilic grease from wool-bearing animals such as sheep or goats, acts as both a waterproofing wax and a bonding agent, giving the shoe polish its greasy feel and texture. It prevents the naphtha from evaporating until the polish has been spread and buffed into a thin film on the leather surface. An essential ingredient in shoe polish is a thickener; without this, the polish would be too runny, making it difficult to use. Gum arabic, a substance from two sub-Saharan species of the acacia tree, is commonly used to increase the viscosity of the product.
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