Composition ornament ("compo") is a mouldable thermoplastic compound, consisting of powdered chalk mixed with collagen (hide glue), resin (pine rosin) and linseed oil; worked either by hand or more usually pressed into moulds to produce decorative work. It's now most commonly seen as part of
gilded picture frames, but was in use for many smaller decorative mouldings from the later part of the
Baroque
The Baroque (, ; ) is a style of architecture, music, dance, painting, sculpture, poetry, and other arts that flourished in Europe from the early 17th century until the 1750s. In the territories of the Spanish and Portuguese empires including t ...
period.
Compo recipes
A basic compo recipe can have many variations.
Some understanding of what each ingredient is doing helps when adjusting the basic recipe, starting with the four essential ingredients:
*
Whiting gives body.
*
Pearl glue
Animal glue is an adhesive that is created by prolonged boiling of animal connective tissue in a process called rendering. In addition to being used as an adhesive it is used for coating and sizing, in decorative composition ornaments, and ...
acts as a binder.
*
Linseed oil makes the mixture soft.
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Rosin
Rosin (), also called colophony or Greek pitch ( la, links=no, pix graeca), is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene comp ...
makes the mixture elastic.
With optional ingredients, including:
*
Venice turpentine
Turpentine (which is also called spirit of turpentine, oil of turpentine, terebenthene, terebinthine and (colloquially) turps) is a fluid obtained by the distillation of resin harvested from living trees, mainly pines. Mainly used as a special ...
prevents cracking.
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Glycerine
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
tempers the glue.
*
Zinc oxide
Zinc oxide is an inorganic compound with the formula . It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement ...
prevents formation of mould.
History
Composition is widely accepted to have been developed by Thomas Jackson in London around the late 18th century. His son, George Jackson, continued the business. His company, George Jackson, still trades today and supplies composition ornament made to the original methods and recipe.
References
{{Reflist
External links
Example piece in the Science Museum Group's collection
Sculpture materials