1. Juicy fruits, such as strawberries, mulberries, etc., should not be gathered after a rain, otherwise it will be difficult to get the juice to form a jelly owing to excessive moisture.
2. Jelly will be clearer and finer if fruit is simmered gently and not stirred during the cooking.
3. Too much sugar will cause jelly to crystallise, and will also make it soft and liquid. Fruit will contain more sugar in a dry, hot season than in a cold, wet one; therefore, instead of using equal quantities, only three-quarters of a pint of sugar should be used to one pint fruit juice.
4. If not enough sugar is used, the jelly will be tough.
5. Jelly must cook rapidly, but not hard.
6. Over-cooking produces a gummy consistency.
7. Crystallisation is due to stirring, too rapid cooking, too much sugar, or storing in a warm place.
8. Too much water in cooking the fruit will injure the quality of the jelly.
9. Jelly will be clearer if juice is allowed to pass through a heavy flannel or felt bag instead of muslin. The process can be simplified by turning the fruit into a colander or straining it through a piece of butter muslin and then through the bag.
10. Do not try to hasten the process of straining by mashing the fruit or forcing it through the bag.
11. In making jelly fruit is as a rule never peeled, as the skins contain a large percentage of pectin.
12. Fermentation is due to storing in a warm, damp place, or not being cooked sufficiently.
13. The best way to keep jelly is to pour hot melted paraffine wax on top after the jelly has been poured into the glasses, and then to adjust the covers. (Paraffine wax can be bought at any chemist, and a sixpence worth will cover several dozen jars.)