Put 2 small heatproof plates or saucers in the freezer to chill. See Note 6.
Wash the apricots and pat dry. Remove any minor blemishes then cut them in half and remove the stones.
Place the apricots in a large, wide saucepan and add the lemon juice and water. See Note 7.
Bring to a simmer over medium heat, stirring occasionally with a long-handled wooden spoon. See Note 8.
Cover the pot and cook, stirring frequently, until the apricots are tender and cooked through, 10-15 minutes. At this stage, if you prefer less chunky jam, you could blend it using a hand-held stick blender. Take the saucepan off the heat to do this.
Add the sugar to the apricots and stir constantly, without boiling, until the sugar has dissolved.
After dissolving the sugar, increase the heat and bring the fruit to a boil to cook the liquid off. Continue to cook, uncovered, stirring occasionally to make sure the mixture does not catch and burn on the bottom of the pan.As the mixture reduces, stir frequently. At this stage, the jam requires your attention so do not venture too far away from the stove. Remove any scum that forms with a spoon.
When the jam looks thicker, after boiling for about 20 minutes, (See Note 9), turn off the heat and put a small amount of jam on a chilled plate. Let it stand for a minute to cool then push your finger through the jam. If it wrinkles, even slightly, it is ready. If it is still quite liquid put it back on the heat for a further 5 minutes and check again.
You can also use a thermometer to check for setting point. To use this method, you will need a sugar thermometer. Clip the thermometer to the side of your pan. When the thermometer reads 104 C (220 F) the jam is ready.
When the jam reaches setting point, remove the pan from the heat. If there is any scum on the surface of the jam, remove with a spoon or add a teaspoon of butter and stir well. It will dissolve the scum.
Let the jam stand for about 10 minutes to allow the fruit to settle. This will ensure that any pieces of fruit will be evenly distributed throughout the jam. Without standing, the fruit will rise to the top of the jar.
Stir the jam and carefully ladle it into the heated, sterilised jars. You need to be very careful. A splash or spill from hot jam would result in a serious burn. I recommend that you wear clothing with long sleeves. Additionally, this is not the occasion to have children nearby. Immediately seal the jars tightly with sterilised lids.
The jam will still be liquid when you ladle it into your jars. It can take up to 48 hours to completely set. See Note 10.
When cool, remove any spills from the jars and label with the date and name. Store the jam in a cool, dark place. When using the jam, always use a clean, dry spoon to avoid contamination. After opening a jar, as a further precaution, store it in the refrigerator.