I use the water canning method. You need a large pot with a lid, a canning rack, wide mouth funnel, fresh and clean towels and a baking sheet.

Bring a pot of water to boil, and sterilize the jars (I use half-pint jars) for a few minutes (Likewise, I know people use the dishwasher to sanitize the jars. Set the sanitized jars on a large baking sheet, covered with a clean towel.

In a separate pot, boil the lids and rims.

In a large pot (I use a non-stick), bring the crushed berries, sugar, pectin and lemon juice to a boil; add the butter.

Allow to come a rolling boil for about 10 minutes; until the mixture appears gelatinous. TIP: I freeze one small plate and a couple of spoons. When the jam coats the back of the spoon, it's ready. I double-check by adding a little jam to the frozen plate, then run my finger down the middle. If it stays apart, it's ready.

Using a wide funnel, carefully ladle the jam into the sanitized jars, leaving about 1/4" of headspace (basically the space from the rim to the jam).

Seal and tight on a rim-- use care, as these are very hot! I wear an oven mitt and turn with a terry towel.

To water can, bring the pot of water back to a boil, and using tongs (I use special canning tongs) drop onto the rack and lower. Once the water comes to a full boil, set the timer for 15 minutes.

Carefully remove, with tongs. You should hear the sweet "ping" of the lids sealing each jar. Some folks say to put the jars upside down. I don't. You decide. Test to see that you have a good seal-- press on the lid. If there is no resistance, you have the vacuum seal you want. If it "gives", you either eat this within 2 weeks (and refrigerate it right away) or you can repeat the water bath for 15 minutes.

Store in a cool dry place; my jam can keep, easily for over a year. But, it's usually gone by then!