Place a small amount on the mixture on the plate. The cold plate will help cool the mixture instantly and give you a good indication if the jam is ready.
You may need to do this once or a couple of times depending on how soon you start checking.
If the blob of mixture you placed on the plate wrinkles when you touch it with your fingers - you know its there.
Just when you are ready to take the jam off the heat add a teaspoon of butter and you will notice that all the foam on the top will dissolve and give you that glossy golden shine.
Let the Jam cool for about 20 mins before you pour it into a warm sterilized jar leaving 1/4 inch of the top.
Use a clean sterilized knife or spatula to move the jam a bit - this will remove any air pockets.
Clean the rim of the jar with a clean paper towel.
Top the lid and screw on rings (that come with the canning jars)
Place a piece of wax paper on the top before you place the lid on tightly.