1. Wash the grapes well in cold water, then pick the grapes off the bunch and squeeze them out of their skins into a stainless steel saucepan. It’s fine if a little skin stays stuck to the pulp. Set aside the grape skins. You will be using them later.
2. Place the saucepan of grape pulp over a medium heat, cover it and bring it to a gentle boil.
3. Cook for about five minutes, stirring occasionally.
4. When the grapes have broken down to a mush, remove them from the heat.
5. Place a large bowl in the sink and set the sieve over it. Pour the grape pulp into the sieve and using a wooden spoon, push down the pulp through the mesh.
6. Add the grape skins to the pulp now and bring it to a boil, stirring occasionally. Boil for two minutes. You’ll soon notice that it’s now a dark purple thanks to the colour of the grape skins.
7. While the jam is coming to a boil, warm the sugar in a 65°C oven.
8. Then, gradually add the warmed sugar to the grape pulp, stirring in one cup at a time. Bring it back to a rolling boil and cook, stirring constantly, until the jam is ready (see notes on how to check when it’s ready below).
9. Enjoy!

How to check if your jam is ready:

• Temperature Test – if the temperature (using a candy thermometer) shows 104ºC, then the jam is ready. Make sure that your thermometer is placed vertically and the bulb is covered with the jam. The bulb should NOT touch the bottom of the pan.
• Spoon Test – this is similar to how you test a sugar thread consistency. Take a cool metal spoon and dip it into the boiling jam mixture. When you lift the spoon, if the jam runs off the spoon like a syrup, then the jam needs more cooking time. But if it is heavier and drops like slate/sheet off the spoon, you know that the jam is ready.
• Refrigerator Test – this is one of the most popular methods. Keep a plate in the freezer and remove it when you’re ready to test. Then, pour a small amount of the boiling jam onto the frozen plate and let it sit in the fridge for few seconds. If the mixture gels/mounds and wrinkles when you push it with your finger, it’s ready. If it’s runny, then continue to cook the jam for few more minutes until it resembles the conditions outlined above when retested.