It is because you are not using commercial pectin. This is a slow cooking recipe. Requires time to cook down. Plus, using a thermometer will be best. Cook to 220 degrees for jams. It will depend upon the variety of the berries, the ripeness, the natural acid and pectin, etc.
I don't want to fuss with these types of jams. I prefer pectin. It is with added pectin that only takes one min. to boil, not this kind of jam.

There are many of these very old recipes from back when folks were either making their own pectin or using none and jams were expected to be much thinner.

But there are much easier ways to make jam and jellies now days. ;) Recipes for many different jams are included in the boxes of pectin made by various brands and you may wish to explore the many recipes offered by NCHFP linked below.

Given enough time - weeks to months - this may thicken up somewhat but if not you can always use it as a syrup.

Here is a link that might be useful: NCHFP - Jams and Jellies

Thank you both, Linda Lou and Digdirt. I feel a little silly now, having realized just how many posts there are RE: jam/jelly not setting. I've been pouring over the vast knowledge in those posts shared by so many of you experienced jammers!

I guess I'm beginning to realize that no pectin jams need more time and are, naturally, a little more variable than using the box of Pectin method. Also, I bet that it's true that traditional jams without pectin were usually a bit runnier. The recipe I used, though, at least produced some delicious tasting jam soup, which I thik is going to end up as syrup! I find that the lemon in it really lends a lot to the end flavour.

Again, thank you both for your responses! Amyjean

10 minutes seems like a fairly short time to me. I never concern myself with watching the clock - I watch the mixture instead, and test it frequently for 'jelling point'. At a rough guess, I'd say it'd be closer to 20 minutes, depending on the fruit. And it should be a full, rolling boil, not a gentle simmer. Obviously, stir often to prevent it sticking and burning on the bottom.

While the jam is cooking, keep a saucer in the fridge, then test the mixture. Put a small amount (say, half a teaspoon) onto the edge of the saucer. Wait a few seconds for it to cool down a bit, then gently push it around with the spoon. If it doesn't get wrinkly, or can't be shaped, keep cooking, and keep re-testing.

It helps to toss in a few GREEN (unripe, or only partially ripe) blackberries which have more pectin than fully-ripe ones.

Also, the lemon juice MUST be from a fully-ripe lemon to get the pectin required from it. You can also add a bit more lemon juice, allowing 2-3 tablespoons to every 2kg (4lb) fruit.

If all else fails, you can always resort to adding some gelatine to it!

Gelatin is a meat product and not considered something to be added to a processed jam. Here the ones with gelatin are meant to be refrigerated.
You can get Clear Jel, which is a modified food starch that can be used in homecanning of pie fillings and jams. That is another option for thickening up the jam. That is true, those cooked jams will be softer in texture. Jam is supposed to be more thin than jelly. Jelly should hold it's shape, like cranberry sauce out of a can. Jam will be thinner. Preserves, thinner yet.

Another suggestion for this batch if you don't redo it into a jam. A great Native American dish is putting small fluffy dumplings into the heated berry "soup" and cooking until they are done. I've seen some people use regular biscuits as the dumpling, just tear the uncooked biscuit in half before putting it into the boiling "soup". One of my favorites. Of course, you eat them immediately with some of the "soup" in the bowl with them.

Well, it's perfectly possible to produce a wonderful blackberry jam without commercial pectin. (And a good full set, not a soft set.)

Certainly no-commercial-pectin jams can result in a soft set, but those would be jams or preserves with low-pectin fruits like pears, not blackberries.

I love making jams without commercial pectin. More effort = more flavor. It's a skill that can be learned.

From my perspective, this is a poor recipe to work with, particularly for an inexperienced preserver, and I'm surprised no one mentioned that.

It's a huge batch. You have 12 pounds of product, which is far larger than is recommended for a traditional preserve.

A traditional preserve batch of this size would require far more than 10 minutes to set and would probably be overcooked before reaching the gel point. The water in the recipe is redundant. You're adding water which you then have to boil off to reach the gel point.

I would recommend doing as Daisy says. Use 1/4 underripe fruit to increase the pectin level. Cut the batch in half to reduce the cooking time. Macerate (soak) the fruit in the sugar to dissolve it (i.e. leave the blackberries and sugar in a bowl about 12 hours so the sugar liquifies). Forget the water. Use the lemon and add the pulp when you ream it. Then you'll have a preserve that will set beautifully and will have a flavor to remember.

This is a craft. It's artistry and requires devotion.

Carol

Another way is to add a few apples to the mixture. Apples are high in pectin.

Thank you all for the responses. One thing I don't understand is pectin. I thought that commercial pectin is made from apples. Why would there be much difference in using natural (i.e. from adding lemon) versus using "commerical"? I guess I realize that when adding lemons or apples or unripe fruit there is a variable in that you don't actually know exactly how much pectin is in the fruit. However, I've read that you can ruin the pectin (the source I read was talking about commercial pectin) by cooking it too long. Wouldn't this be true for the "natural" pectin found in the added lemon as well?

Also, ReadingLady, I am very much interested in "cooking the old way" for several reasons --one is just not having to be dependent on running to the store for pectin; also paying for pectin, but also, I just tend to like the idea of doing things simply and the "traditional" way. And now, from reading your post, I think you imply that jam without commercial pectin might taste better?

By the way, I appreciated the comments re: the recipe, specifically. I will use a smaller batch, no water recipe next time.

Sorry for the long post, but I am so excited to learn and "master" this art!

Once again, Thank you everyone

Pectins are made from some high pectin fruits or seeds. Pomona pectin is different as it is citrus based and needs no sugar or lengthy boiling to set. Instead, you add a tiny amount of calcium (packed with it) to it and it sets up quite well even with no sugar added. A single box of Pomona can make up to 30 cups of jam or jelly. NEVER use gelatin as its a protien base and as mentioned would require lengthy heat processing to be safe. Gelatin doesn't remain stable either, and can break down once heated too much.

I don't know if this is a idea that you would want to use but it makes terrific jam. My mother used cortland apples, I'm not sure if this was to stretch the blackberries, for pectin or because the apples were available. It basically is the only jam that I eat. I use 3 1/2 cups of berries and 1 1/2 cups of hand chopped apples. Don't use the processor because it breaks down the pectin. You can chop as fine as you like. Hope this helps.

I don't understand the science of pectin either. But I've never in my life used the commercial stuff, and have never once found it necessary. In fact, it wasn't until I got into these American discussion forums that I learned that people actually use the stuff! It does seem to be a peculiarly American thing to do. Much like the BWBing thing, which I've never done for jams and such.

Natural pectin content in fruits varies greatly. Even tomatoes have pectin in them. Unless a lot of boiling and sugar is added to help natural pectin to set, its difficult for a person just starting out to make a successful jelly or jam with no added pectin. Some don't use any added pectin, but because diabetics must watch sugar intake its not a good idea to attempt it unless you have a lot of experience. Simply boiling down apple cider to at least 1/20 of its original volume will give a syrup and possible set. Adding things like peels, seeds, septa, and any hulls that surround seed cavities can help improve a natural set. Things like pepper jelly and others with very low amounts of natural pectin will simply boil down to syrup, or scorch badly before reaching any kind of set. Many people here have just strated out trting to make a home canned food. If they follow someones very old recipe and find it to be a failure, the person may not want to try a failure again. Pectin concentrates are quite common in the US and for most fist time jelly makers its a good idea to follow a recipe exactly before attemptng to set a jelly that has no added pectin and is also low in sugar. A BWB IS necessary no matter what place on earth you live on. The UK may not think its necessary, and is perfectly safe to can without any BWB, but thats simply giving dangerous and unpredictable safety to home canned products. I push the envelope some when using a steam canner, but because the canner has a rapid recovery and most canned items are high in acid, I don't worry as much about contamination. I would NOT home can without knowing about an alternative process that is done by commercial companies, and if its possible to duplicate some of these processes. Again, all high acid foods, which, by themselves are safer to home can compared to a low acid food that requires a PC and very high over 212 degrees F heating.

Hi,
I can Blackberry Jam following the Berry Jam recipe from the Ball Blue Book every year. It doesn't have pectin added, and it sets wonderfully. It is thick, not runny at all.
Remy

Yes, there are some recipes for jams that don't need pectin. It relies on the natural pectin in fruits. Obvioulsy things like cranberries are very high in natural pectin and only need plenty of sugar to set. If your watching sugar intake, it may not be a suitable thing to do. Here, being diabetic requires me to watch all sugar intake, and avoid high sugar jams. Instead I use Splenda and a little honey, but Splenda will NOT set the natural pectin in berry fruits, so I resort to Pomona.