This section is from the book "The Gardener V2", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The following is an excellent method of making Quince jam, and a very simple one: - Take 12 lb. of Quinces, pared and cored; cut them into small pieces; put 12 lb. of white sugar into a preserving-pan, with about a quart of water; set the sugar and water on the fire; when they come to the boil, put the Quinces in gradually without taking off the pan; let them boil until the fruit is all soft and of a bright-red colour. Be sure to take off the scum as it rises. A little essence of lemon or cloves will improve the flavour. This jam, if properly boiled, will turn out of the jars when wanted, and may be cut with a knife.