Recipes

• Follow instructions carefully: If recipes says to "boil hard for one minute", use a countdown timer.
• Decide what measurements you will use. Do not mix decimal and imperial.
• Measure the ingredients: Ensure that the right amounts are used, as fruit, pectin, acid and sugar have to be present in the correct amounts for jam to "set".
• Never reduce the amount of sugar: Jam made with reduced sugar will not form into a gel.
• Do not double a recipe: This can cause under cooked conditions. If longer, caramelized flavour.

Mould

• This can occur if the cellophane seal cover is applied while the mixture is too hot. The wax disc is fitted when the jam is about 180°F - 81°C but the clear seal when the product is cold. If still hot when fitted condensation will trap water and cause mould.
• Loose lid or clear cover.

Fruit

• Always use fresh, slightly under ripe fruit. As fruit becomes ripe the natural pectin content decreases and the setting ability of the fruit is reduced.
• Finely chop all fruits as this gives a larger surface area allowing the flavour and pectin to be released quickly.
• Wash all fruits where possible. Oranges, apples, may have been sprayed for pest control or to aid keeping. Lemons are "waxed" to prevent spoilage, "unwaxed" can be purchased, but still wash.
• When making jellies with currant fruit the complete sprue can be cooked as the straining will only extract the juice, then the stalks can be disposed of.

Cloudy Jelly

• Juice was not properly strained. Jelly is best left to drain through a very fine jelly bag not a sieve. Do not try to squeeze the juice.
• Pouring jelly mixture into jars too slowly.
• Allowing jelly mixture to stand before potting.
• Fruit used is extremely high in pectin (if jelly sets too fast, air bubbles are trapped in it, giving a cloudy appearance).

Sugar crystals in product

• Misread recipe (too much sugar).
• Mixture cooked for too long, reducing the liquid to sugar ratio.
• Cooking the mixture too little. When sucrose is boiled in acid fruit juice to make jelly, some of it is "inverted", or broken down, to dextrose (glucose) and levulose (fructose). Sugar would probably crystallize from most jellies if it weren't partially inverted during the cooking process. Too little cooking results in insufficient sucrose inversion. This is rarely a problem in jellies made without pectin since they require fairly long cooking time.
  However, sugar may crystallize from jelly made with added pectin because the boiling time is too short to bring about much inversion. So ensure that when using added pectin, the sugar is well dissolved.
• Crystals that form at the top of jam that has been opened and allowed to stand are caused by evaporation of the water.
• Needle-like crystals in grape jelly may be tartaric acid, the natural substance in grapes from which cream of tartar is made. To prevent formation of tartrate crystals in the jelly, let the extracted juice stand overnight in refrigerator, then strain through two thickness of cheesecloth to remove crystals.

Jam too soft

• Under cooked
• Made as a too bigger batch. Do not double the recipe.
• Too much juice in mixture. For jellies ensure that the juice is measured and the right amount of sugar to juice is added as the recipe.
• Too little sugar, do not decrease the amount in recipe.
• Made with a great excess of sugar.

Vinegar problems

• Too soft: Vinegar products which have had insufficient cooking, to ensure complete takeup of vinegar. Cook until a spoon trailed across the bottom of pan is not filled by a back run of liquid.
• Fruits too tough: fruits such as damson and plums require pricking with a fork too allow the vinegar to penetrate.
• Shrinkage in jar: Poor airtight seal, poor potting leaving to much airspace as stored products settle.