Yes...this is a lot of sugar. A LOT. But, as I always say, when you make it at home, you know exactly what goes into your food. You can cut down on the sugar, down to about 4 cups, depending on how sweet your fruit is, and how sweet you like your jam. The 6 cups in this recipe will give you a result of a store bought jam.
The lemon juice and sugar will do a wonderful job of breaking down the berries. This is also called macerating (mass-er-ating) if you're wanting a fancy term!
At this point, if you don't have a stick, or immersion blender, I would go on and put these through the food processor or a regular blender to puree these down to a smoother consistency. You can make it as smooth as you want, or, if you like some chunks of berry left, leave it as chunky as you want! I have a stick blender, so I started cooking my jam down, and planned to blend it during the cooking process.
As your jam cooks, it will foam. Don't worry! This is supposed to happen! Just take a spoon and skim it off, and continue to cook the jam.
As the jam cooks down, it will thicken and release pectin, which is what will help it set up as it cools. The jam should cook anywhere from 30 minutes to about 1 hour, on medium heat. I know that isn't very helpful, but there are a lot of variables that can change how your jam is going to turn out; the humidity of the day you're cooking, the ripeness of the fruit, the heat on your stove...you get the idea. I like to do a variation on my spoon method to test my jam; I'll dip the back of a spoon which has been in the freezer for 30 minutes, into the jam, and once it has cooled for a minute, run my finger through it. If the jam stays parted, I consider it ready to be ladled into the waiting (still hot) jars.
Conversely, and a more commonly accepted method, is called the "wrinkle" method. Before starting the canning process, put three or four heatproof saucers into the freezer. When you feel like you want to test your jam, to see if its ready to pour into your jars, take a saucer out of the freezer, and spoon a little of the jam onto the plate. Let it sit for a minute, then push at it with your finger. If the surface of the jam wrinkles, then it has set, and is ready to ladle into your jars. If it is still liquid, then let it boil for another five minutes and try again!
My spoon method:
Here is my wide-mouth funnel. I tried for a couple of years without one, and it is possible, of course, but it is so much easier with one! You want to keep the rims of the jars clean, so you can get a vacuum seal after you process the jars, so having a funnel sit on the inside of the jar, makes life easier!
I like to fill my jars up to the first ring. This will leave about 1 inch of headspace, for processing. If you have too much, or too little headspace, you may not get the vacuum seal after processing.
Even with the funnel, you still may get a little mess on the rim. No worries, with a very, very (did I mention very??) clean towel, wipe the rim of the jar, and continue on your way!
I have a magnetic wand that I run in the dishwasher sanitizing cycle with the jars, to get the lids and rings out of the hot water. If you don't have one of these, use the sanitized tongs to get the lids out of the hot water!
Don't be afraid of canning, it is really easy and not nearly as scary as it seems! And, if you have some jam that doesn't set up to the jam consistency you were wanting, that's no problem either! It's just a lovely syrup for ice cream, waffles, or pancakes! You were totally going for that consistency, right?? Right? No one else has to know!