A blanket is a piece of soft cloth large enough either to cover or to enfold a great portion of the user’s body. It is usually used when a person goes to sleep or is otherwise at rest. It traps radiant bodily heat that otherwise would be lost through convection, helping to keep the user warm. Many children and adults use a blanket as a comfort object. Many types of blanket material, such as wool, are used because they are thicker and have more substantial fabric to them, but cotton can also be used for light blankets. Wool blankets are warmer and also relatively slow to burn compared to cotton. The most common types of blankets are woven acrylic, knitted polyester, mink, cotton, fleece and wool. Blankets also come with exotic crafting and exotic material such as crocheted afghan or a silk covering. The term blanket is often interchanged with comforter, quilt, and duvet, as they all have similar uses. Blankets have been used by militaries for many centuries.[6] Militaries are some of the biggest single consumers of woolen blankets. Military blankets tend to be coarse grey, with thick fibers of over 20 microns. Special blankets known as baby blankets are used to protect infants from the cold. Small children (and some adults) may also use a blanket as a comfort object. Blankets may be spread on the ground for a picnic or where people want to sit in a grassy or muddy area without soiling their clothing. Temporary blankets have been designed for this purpose.