First, gather your ripe berries and set aside at least 1 pound to make jam. It is so tempting to eat all the berries, which is why I loved going to a YouPick farm this year. You can eat your fill and still have enough for jams, sauces, and desserts for a small cost.
Once you have your berries whether they are ripe or frozen from the grocery store (either way works) place the berries and about 1 cup of granulated sugar in a sauce pan. Mix the berries and the sugar together and let cook for about 15 minutes or on medium low heat.
Once combined smash up the berries with a potato masher. All of the juice from the fresh berries will go into the sauce pan.
Bring the sugar and the berry mixture to a full boil and then add in about 1/4 bottle of lemon juice. I like to use the actual bottle of lemon juice because the acidity levels are usually higher than just fresh squeezed lemon. Let all of the ingredients meld together for about 15-20 minutes. It is really important to let the berries, sugar, and lemon juice cook together well so it will properly set later on. If your berry mixture is too thin and runny it just means it was not cooked long enough. Error on the side of cooking longer versus shorter.
If you want to add a touch of pectin in, now is the time. Do not cook for longer than 1 minute with the pectin so be sure to add it at the very last minute (quite literally).
Once this simple blackberry jam is cooked to perfection, get out your jam jars and leave about 1/4 inch head space at the top. Use your funnel and pour the jam inside! Secure the lids and rims and wipe clean. You are now ready to give your jam a water bath for 10 minutes. Once they are done boiling in the water at least 1-2 inches high carefully take them out and let them sit on the counter uninterrupted for at least 12 hours. Check the seals and if the button gives or pops up. They are good to go.
Store in the refrigerator for at least one month. Store in the pantry for 1 year if they are properly sealed. If you do not want to mess with a water bath, this step can be skipped and you can let the jam rest at room temperature for at least 12 hours. The jam will not last as long though. Up to three weeks in the refrigerator.
