You don't need a jam thermometer to make this delicious blackberry jam.

Reader Sam Dixon reveals the secret to making simple blackberry preserve without a jam thermometer.

I developed this blackberry jam from a recipe for raspberry preserve that I already had. The fruits contain similar amounts of natural pectin and so need the same amount of help to thicken.

You can make a big batch and pour it into jars, but I usually just make a small amount to fill a sponge cake or for a special brunch.

blackberry jam


1. Weigh out twice as many blackberries to caster sugar and place in a very large pan.

2. Add a couple of tablespoons of lemon juice to help the preserve thicken.

3. Bring to boil and then let simmer without stirring for 20 minutes.

4. Do the fridge test. Dollop a little of the jam liquid on a cold plate and put in fridge for five minutes. If it sets then it’s ready. If not, keep cooking and testing every five minutes.

5. If you’re using jars, rinse them with hot soapy water and dry in a hot oven while preparing your jam. When it’s ready, pour in and screw the lids on tightly.


  • Horace Coker

    I agree. The traditional ratio of 1:1 is the best. I spice mine up a bit (also bramble jelly) with juniper berries, cloves, cinnamon and cardamom.

  • Horace Coker

    Well thanks for that but it doesn’t work. There isn’t a symbol for Disqus in the way that you describe but something else that doesn’t allow a comment to be made.

    How are you?

  • super stevens

    Just saw you were there so I just wanted to talk. Yes you can still have an access on Disqus. Next to each album there small icons on the left like “Share on Facebook” the last one is comment on Disqus. You can do so for any other pages as well : greatest artists, guitarists, singers…
    For blackberry jam, I never tried to make it as I am lazy at cooking. I prefer eating it! 🙂

  • Horace Coker

    Haha! What are you doing here?
    I can’t access the comments section on RS. In fact I thought it had been shut down.
    Can you possibly help? When I log on to the RS site there is no mention of Disqus anywhere

    Do you like making blackberry jam?

  • super stevens

    Hey Horace! Did you give up with Rolling Stone?

  • Jools

    Have always used the rule 1lb of fruit to 1lb of sugar. But searched for blackberry jam recipes yesterday and tried this one. I should have stuck to my tried and tested rule. This jam is very tart as there really is not enough sugar in it for my, nor my family’s taste, so beware, if you like sweet jam don’t use this recipe.
    I only made 3lb so not a total disaster.

  • Horace Coker

    Why no comments?