Serge is a name given to a class of twill woven goods with a worsted warp and either woollen or worsted weft, dependent on the specific type.
In the 18th and early 19th C they were generally produced in relatively loose textures required for linings of coats and cloaks. For such applications a fabric which is fairly soft is required so it will conform to the outer garment without making it too stiff.
Some pieces were milled to give them more body and were used for applications requiring more body, but not the density of Kersey or Broadcloth, such as the sleeves of soldiers working jackets, where flexibility was more important than density.
Later in the 19th C some denser types were produced for outer garments, again either all worsted or worsted and woollen, particularly as an alternative to woollen broadcloths for wear in Tropical climates.
Specific Types include:
Common Serge: Coarse quality with woollen weft used for linings of soldiers’ clothing.
Milled Bay: A coarse serge which has been milled, causing the woollen weft to shrink and cover the warp to some extent. Used to give a similar appearance to a more substantial cloth but without the weight, density or expense.
Shalloon: A fine all worsted used for linings in high quality clothing.
Foreign Service Serge: A more densely woven serge produced in the second half of the 19th C, with a woollen weft, heavily milled, used for Soldier’s Frock tunics for working wear and for hot climates.
Khaki Serge: Similar to the Foreign Service Serge but with a mixture Khaki weft.