Incorrect washing and sterilizing can result in mould forming in stored preserves, so it is worth spending a few minutes making sure that your jars are scrupulously clean and properly sterilized.
The jars and bottles you use, especially if you are giving preserves as gifts, can affect the look of the jam enormously. A huge variety of shapes and sizes are available, and for that reason the recipes in this book give the final quantity of jam as a simple measurement, so you can work out which of your jars would add up to that total the best.