One pound of raspberries equals one pound of sugar. Which means equal quantities of both fruit and sugar. This recipe makes approximately 1.5 pounds of jam.
1lb granulated sugar or jam sugar with added pectin
Put the fruit into a large pan and mas it with a spoon or potato masher. Heat gently until the fruit starts to boil. Add the sugar and simmer over a low heat. Stir until the sugar dissolves. Once the sugar has dissolved boil rapidly until setting point is reached. Transfer to sterilised jam jars and seal.
There are various ways to test if your jam has reached setting point. The one I use is extremely straight forward and is called the wrinkle test. Spoon a little jam onto a cold plate. Allow the jam to cool and then push it with your finger. If the jam has reached setting point it will wrinkle on the top. If the jam shows only slight wrinkling, boil for a few minutes longer and test again.