Composition ornament ("compo") is a mouldable
thermoplastic
A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains as ...
compound, consisting of powdered chalk mixed with
collagen
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
(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 Western Style (visual arts), style of Baroque architecture, architecture, Baroque music, music, Baroque dance, dance, Baroque painting, painting, Baroque sculpture, sculpture, poetry, and other arts that flourished from ...
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 acts as a binder.
*
Linseed oil
Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colorless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...
makes the mixture soft.
*
Rosin
Rosin (), also known as colophony or Greek pitch (), is a resinous material obtained from pine trees and other plants, mostly conifers. The primary components of rosin are diterpenoids, i.e., C20 carboxylic acids. Rosin consists mainly of r ...
makes the mixture elastic.
With optional ingredients, including:
*
Venice turpentine prevents cracking.
*
Glycerine tempers the glue.
*
Zinc oxide
Zinc oxide is an inorganic compound with the Chemical formula, formula . It is a white powder which is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, Zinc metabolism, food supplements, rubbe ...
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