My mother and I always picked lots of blackberries. It was something that we both enjoyed doing. My mom made the best blackberry jam. Over the years she would change the recipe a bit, sometimes only using honey, and sometimes using sugar. When I was little she used pectin also, but not with the honey. Usually she would leave out the pectin, and just use sugar instead. I often would help her, but I never made it on my own.
I looked up a few recipes, it seemed that many require the same amount of sugar and berries, 4 cups for instance of blackberries, and 4 cups of sugar. For this batch of blackberry jam, organic sugar was used and no pectic. In order to make the jam thick it was boiled it a little longer than usual. There were lots of blackberries so much jam was made!.
In addition, I made seedless blackberry jam also using a food mill, which turns and smashes the berries and the seeds are separated.
After that I cook the blackberries down a little more to make sure they are thickening, and then pour into sanitized jars. I sanitize the lids, bands, and the jars, and use directly after sanitizing. Which I did with the dishwasher, it has a “sanitize” setting.