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I made blackberry jam last night, the first time I've ever tried making jam!  It seemed to work okay but I think I left it a bit long as it was pretty solid when I tried to spread it this morning!  Tasted good though  ;D

So, is there a foolproof way to make jam so it's just right or is it always hit and miss / experience?

Also after reading the thread about mould on jam, can anyone direct me to a good source of how to prepare jars and what to do?   I'll admit that I washed the jars, boiled them, bunged them in the oven and then used them!  But I only made a few jars so I figured they wouldn't last long anyway.  :D

Next question, what can I do with quite solid jam?  I know I could make jam tarts but what else?

THANKS   ;D

Judging the setting point comes with experience, I'm afraid, and berries are difficult anyway because the amount of pectin in them varies.  Although I'm told you can do clever things with a thermometer I've never bothered.  I use two "eye" tests.

The first is a drip tests.  Put a wooden spoon in to the pan, and lift it out, holding the bowl of the spoon vertical.  When jam is getting to a set the juice tends to tear rather than drip.  It's easier to see than describe.


The second is a plate test. Put a thing layer of juice about an inch long on a cold plate.  When you push your fingernail through it, the juice will wrinkle rather than flow out of the way.

If it's gone really solid, try adding it to apple crumble, or as the base for a steamed pudding.  Keep trying though because home made jam is far nicer than shop bought, and there are so many different mixes you can use.

I made apricot and mango for the first time this year, and it's very nice.

We made our 1st jam this year.The 1st batch wouldnt set but thanks to some great advice we reboiled it and used Certo which you can buy in a bottle from Sainsburys.Our 2nd batch we made using sugar with added pectin and this was a great success.I think if you use certo or the sugar with added pectin it makes making the jam idiot proof and you don't have to boil for very long.

Thanks to advice from EJ, I have just corrected some solid strawberry jam. For two 1lb jars, I made a sugar syrup (half pound sugar and a splosh of water - prob about quarter pint) , added the solid jam and gently heated through and mixed, then boiled up for a couple of mins, re-tested, and it was a much nicer set. Put in freshly sterilised jars.
I am not sure if it will keep as well as when first made, but it is such an improvement that it won't hang around very long.

Jam making is fairly straightforward as long as you follow some rules.
Fruit varies in water, pectin, acid and sugar content, and as these are vital for the setting process, there will be some differences in each batch of fruit you use.
Use good quality fruit, only just ripe if possible. Don't use bruised fruit.
Prepare it, weigh it and make a note of the weight.
Wash it thoroughly, and cook it well before adding any sugar. Cook it in as little water as possible, a pressure cooker is ideal, or it can be microwaved in small quantities.
If the fruit is low in acid, add the juice of a lemon to every kg before cooking. The fruit should be soft, and some such as blackcurrants need to be checked that the skins are soft before the sugar is added.
The cooking brings out the pectin in the fruit, You can test for pectin by putting a few drops of the juice in an egg cup, letting it cool, and, well away from the cooking area, add a few drops of methylated spirits to your sample. After a couple of seconds, the juice will have formed a jelly-like blob which will hold its form when tipped out onto a plate. Don't do this anywhere near your main pan, and don't add it back to the fruit. If your sample doesn't form a firm blob, there isn't enough pectin there to set the jam, so cook a little longer and re-test - you can add more lemon juice to help the process.
Only then add the sugar, and use the same weight as the fruit, so if you had 1kg of fruit, use 1kg of sugar. For fruits with a high water content such as plums, strawberries etc, add only 95% sugar. It's better to cook these a little longer to reduce the water content, before adding the sugar . I use granulated white sugar and have found no difference at all between beet and cane sugar.
Stir the sugar in to dissolve it and then using full heat, bring the jam up to 104 degrees centigrade  and hold it there for around three to four minutes. It may take around 10 to 15 minutes to bring the jam up to this temperature depending on the amount of jam you are making and the size of the burner on your cooker.
Use the largest burner with the highest heat output. Place the pan centrally on it before starting.  Stir slowly to avoid the jam catching at the bottom of the pan.
Use a stainless steel pan with a very thick bottom, 10mm plus is a good thickness to distribute the heat well, and the pan should overlap the edges of the flame if you are using gas. Don't move the pan during cooking or when you are filling the jars, jam causes nasty burns.
Use new jars if possible with new lids. Jars can be sterilised by washing thoroughly and heating in the oven up to 120 degrees C for five minutes, then turn the oven off and leave them there until required - this is best done at the start so they have time to cool down a little before you use them. Lids can be steam sterilised. They should be kept in a warm place prior to use, this makes the sealing compound pliable. I only use new jars and lids, so won't try to advise on re-using old ones or using the cellophane jam covers.
The advice given by silverbirch on drip tests and plate test is a good way to check, the drips do have a jagged appearance when the jam is ready and hang on the ladle.
You could ladle out the jam into the jars direct, or via a jam funnel, or into a pyrex jug then use this to pour into the jars. Keep the jam at over 90 degrees whilst doing this to ensure it's above sterilise point. Don't try to tip the pan direct into the jars, it's dangerous.
Leave a small gap of about 6mm between the jam and the top of the jar. Put lids on straight away, and  tighten. As the jam cools, the air gap will contract, causing the lids to depress and form a firm seal.
I don't use commercial pectin, it's expensive and not necessary if the fruit is handled and cooked properly in the first place.

Edited to add: On sealed jars, if you shake the jar of jam, or turn it upside down before it's cooled right down, this may help to mix any condensation on the underside of the lid back into the jam. This would ensure that the jam at the top carries the same level of sugar and may help prevent mould growth.