True to my intentions last weekend (Blueberries, Blackberries and Decoupage), we did actually make and can blackberry jam this week. I'm not going to tell you the technical details, the whys and the how-to's of the canning process, because there are much better instructions available online (National Center for Home Food Preservation) then I could give you. Not to mention that our jam making was a bit of a comedy, so you probably don't want my advice anyway.
First of all, you should start with a good recipe for jam. Unfortunately I don't have one to give you. If you have one, please let me know, because the one we used was distinctly mediocre. It probably should have been intuitively obvious, but a ratio of 6 cups of sugar to 5 cups of blackberries yields a jam that is much, much too sweet. It did gel nicely, thanks to all that sugar and the pectin we added. Unfortunately the pectin also has a strange citrus-y smell that I'm not crazy about. The jam is not bad, but it's nothing to write home about. It's edible, and it's ok on peanut butter and jelly sandwiches, but it just doesn't have much flavor other than sweet.
Second, make sure you and your jam making team are on the same page. My husband and I just aren't a great team in the kitchen. There's a reason that we generally consider the kitchen his and I stay out of the way, and it's not only because he is a good cook and I don't enjoy food preparation all that much. It's also because we have completely different attitudes towards cooking. He is a very creative chef with a tendency to figure things out on the fly and alter recipes as he pleases. I like to read the directions at least once and maybe twice before beginning, have all my materials prepared and ready and execute each step precisely. It's not really a great combination in practice. Especially when trying a completely new technique that has lengthy instructions that threaten dire food poisoning if you mess up. We got through with a lot of patience and courtesy for each other and the occasional gritting of teeth, but let's just say it didn't flow.
Third, it's hard to work with boiling water and boiling sugary jam with an almost four year old daughter underfoot. I had dreadful visions of parents tripping, hot sticky liquids splashing, and widespread third degree burns. We ended up chasing her out of the kitchen to go draw pictures of us making the jam. Which she did, but it wasn't the wholesome family project we were hoping for. She did help me affix the labels to the jars once they were cooled the next day but I think she felt left out. She won't eat the jam, either.
All in all, it goes to show you there's a learning curve for everything. All in all, I would consider our first efforts at canning a reasonable success, despite the comedy. We did actually make jam. We did manage to preserve it in glass jars which we sterilized and sealed in a boiling water bath as instructed. All the lids "popped" and became concave as the instructions described, which means we correctly drove the air out of the jars creating a vacuum that (along with the sugar and acid in the jam itself) will prevent the growth of bacteria. The 8 pounds of blackberries we picked are no longer in danger of spoiling. We have many half-pint jars of blackberry jam sitting in the pantry now and they look very pretty. I estimate that it will probably take us about a year to eat our way through it, which I suppose will take us right up to next year's blackberry harvest so that we can try again. You know, I can't wait!