This section is from the book "The Steward's Handbook And Guide To Party Catering", by Jessup Whitehead. Also available from Amazon: Larousse Gastronomique.
It is what remains when meat liquor is boiled down till nearly dry; it is extract of meat; it is meat gravy dried down thick enough to set solid when cold. It is improved by the cooks by flavorings of herbs, etc., added while it is boiling, and is strained and skimmed, making it a brown, stiff jelly; but that frorrj chicken and veal is not dark, and is mentioned in cooking directions as white glaze. Used to add to sauces to make them rich and meaty, and to enrich soups when the meat is insufficient; also used to glaze or varnish over cooked meats and vegetables before sending- them to table, making them glossy and tempting in appearance. "The glaze is melted like glue and applied with a brush like varnish; a glaze-pot is made on the same principle as a glue-pot. I remember some years ago getting up a dinner where the kitchen windows abut upon the pavement of Park Lane, by Hyde Park. I was engaged in glazing some hams and tongues, when I became aware that my proceedings were being intently watched by a group of street arabs, one of whom could contain his feelings no longer, but shouted to his pals: 'Hi! look 'ere, see! why, the cove in the white jacket is a-varnishing the meat' Buy glaze from the chefs in gentlemen's families; the ordinary glaze of general commerce is made from beef only reduced to a sort of glue, but a chef's stock or bone-pot in a good family contains beef, veal, and the carcasses of poultry and game, thus forming a much richer and tastier glaze than if from beef only, which is comparatively insipid.
After the soups and sauces are made from the first boilings, the pot is boiled up with all the scrap bones and meat cuttings and all other good things; it is then strained off and boiled down rapidly until it assumes the consistency of glue; it is then poured into skins while hot, or into basins and solidifies into solid essence of soup, differing from the essence of beef sold by manufacturers, in the fact that it contains the gelatine as well as the meat, poultry and game essences. You can sometimes arrange to buy this glaze from chefs at 2s. 6d. per lb., as after reserving an abundant supply for family use, the overplus is generally the chef's perquisite. This glaze dissolved in boiling water and boiled up makes splendid clear soup".