Add the sugar to the grape mixture and stir until dissolved; add lemon juice

Bring to a boil, reduce to simmer; stir constantly (skim foam, if necessary)

Jam should be set in about 15 minutes

Fill jars with hot mixture, leaving ¼ inch heasdpace

Wipe the rim clean, centre lid on jar and screw to fingertips tight; do not over tighten

Store in fridge for up to three months, or process

Scale all ingredients into TM bowl on R(reverse); set time for 25 minutes, temperature to 100F and speed to 2

Place teatowel over machine to avoid any splatter; check for set after 20 minutes (cook 5 minutes longer, if needed)

When set, fill jars with hot mixture, leaving ¼ inch heasdpace

Wipe the rim clean, centre lid on jar and screw to fingertips tight; do not over tighten

Store in fridge for up to three months, or process

Fill canner 2/3 full; bring water to a boil

Use canning tongs to place jars into hot water; cover canner and bring to a boil for 10 minutes (start counting the 10 minutes when the water starts to boil)

Turn off heat, remove lid, let the jars sit in water for 5 minutes before removing

Place jars on a heat-proof surface with canning tongs undisturbed for 24 hours

Check seals to ensure jars have sealed properly; store in a cool, dark place

Temperature: apply enough heat to the fruit and sugar to raise the temperature over the boiling point of 212 degrees and alter the structure of the sugar; jam reaches its ideal set point at 220 degrees (a beeping thermometer is great!)

Sugar: if you reduce the amount of sugar in your recipe too drastically, you may not be able to get your jam to the set point

Plate Test: take an ice-cube tray (or a frozen plate ready for this test) from the freezer); place a small dollop of jam on it

After a minute, gently prod the puddle of jam with your finger; if a surface skin seems to be developing a certain solidity, it is done (If it is runny, keep cooking a bit longer)

Sheet Test: (This is the one Grandma Maude taught me.) Using a wooden spoon, stir the jam and lift it up side ways, or horizontally over the jam and watch the jam drip off of the spoon

If the drips come together in a fall of the spoon separately, the jam needs to be cooked longer; if the drips join together in a "sheet" or a thick wide drop, the jam is finished