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Jam Making: A Guide

Julie’s Jamstravaganza

If you’ve never made jam you should give it a go. I’m not going to lie and say it’s stress-free as it involves boiling hot liquid, glass and uncertainty, but with the right preparation it’s fine. The results are always something to be proud of and even the ones that won’t set are delicious in natural yoghurt.

You will need some jars (4 x 375g jars per 1kg of fruit), waxed and cellophane discs (widely available in supermarkets, Woodies, etc) if you don’t have lids, tea towels, a wooden spoon, a large metal spoon,  a large wide saucepan, a saucer,  a potato masher and lemons (for strawberry/blackberry jam), a funnel or jug, and the same amount of sugar as berries.


  • The jars can’t have had anything pickled in them as the glass holds onto the vinegary smell. Kilner jars are great, but make sure they’re 100% glass, not plastic if oven -sterilizing them. I had a Dali moment the first time I did this. To sterilize them wash them in hot soapy water and place upside down on a baking tray in a 120c oven for 15 mins or through a hot cycle in the dishwasher.  Include lids if you have them. Leave the jars upside down on a clean tea towel with any lids until you need them.
  • Put the sugar in an ovenproof bowl(s) and warm it up in a 180c oven  for 15 mins.
  • Put a saucer in the freezer so you can test the jam on it later.

Here comes the science part. Pectin is what sets the jam. It’s in some fruit more than others. So if you have a low pectin fruit (strawberries, rhubarb or pears) you can mix it with a high pectin one (gooseberries, apples, plums or blackcurrants).  Blackberries, raspberries and apricots are medium pectin. Over-ripe fruit is always low in pectin.

Acid draws out the pectin and prevents the sugar crystallizing so fruit low in acid (strawberries and blackberries) should have lemon juice (2 lemons per kilo) added at the beginning.

I”ve provided three basic jam recipes below. Don’t be afraid to mix it up. My garden is full of fruit bushes that were bought in Aldi and Lidl and they need very little looking after. With the awful summers we’re having I’d recommend putting strawberries in pots or hanging baskets as slugs demolish them on the ground.

Strawberry Jam

  1. Prepare everything as above. Hull the fruit and only wash it if it’s very dirty. Place 1kg (or whatever you have) of strawberries with juice of 2 lemons (adjust accordingly if less strawberries) in a large pot over a medium heat. You can mash it up to be as smooth/chunky as you like.
  2. Bring to the boil for 2 mins until the juices flow.
  3. Take off the heat and add the warm sugar, stirring to dissolve it
  4. Put back on the heat and boil for about 10 minutes, stirring from time to time to prevent sticking. Scrape any pink froth off the top with large metal/slotted spoon to remove impurities.
  5. Take out your cold saucer and spoon a little on to it. Let it cool for a minute and then push your finger through it. If the jam wrinkles then it has formed a skin and has set.  You can also lift some out with your wooden spoon and let it cool a little. Then let it run off. If it trickles into a thin stream it’s not ready yet.  Another option is to use a sugar thermometer to see when the jam is at 105c. If, after potting, it seems like the jam isn’t setting  you can always throw it back in a saucepan the next day and boil it up again (taking care to re-sterilise your jars). It’ll be a darker colour and reduced but still fine. Or you could just leave it and call it a coulis or jam gravy or something. NO-ONE NEEDS TO KNOW.
  6. Remove the pot from the heat and pour/spoon into jars. Use a towel to hold them when hot. If there are large pieces of strawberries in it let it cool for 10 mins to prevent them rising to the top. If it’s smooth it’s ok to cover straight away. Cover with lids or wax discs (waxed side down) and cellophane secured with rubber bands.

Raspberry Jam

As per above but leave out the lemon juice and there’s no need to mash them. Just put them in the pan, bring to the boil, cook for 2 mins until juicy and then add the sugar and carry on.

Variation: adding some chopped bramley apples at the start increases the pectin level and tastes delicious. Just make sure you have the same amount of sugar as the raspberries and apples combined.

Gooseberry Jam

As per above but add water to the top and tailed gooseberries in the pan. This is my mum’s recipe and she adds 1/3 pint water per pound of gooseberries and you could include a few tablespoons of elderflower cordial if you have it.  Bring to the  boil and then simmer for about 10 mins to soften. Then add the sugar but don’t stir (she says stirring this jam encourages crystallization).  Still scrape any scummy froth off the top though. After about 20 mins of boiling the jam should be ready.

Do you make jam? What”s your favourite jam recipe?


  1. Just in time for blackberry season! Really useful, thanks Julie. I don’t like strawberry jam or strawberry anything except strawberries, but I could happily live on raspberry jam, eaten with my fingers from the jar.

  2. Thanks foodface. Fingers are indeed nature’s cutlery. I’ve since found out that you can get bottled pectin as easily as in Tesco (it’s defo on their website anyway). Good luck! J.

  3. Can’t get the waxed discs anywhere tried Woodies, Dunnes, Euro store, Inspiring Ideas, Homestore & More to name a few