Prepare jars according to the water bath canning directions.

Chop plums into small-ish pieces. Leave them larger if you like your jam a little more chunky.

Combine chopped plums, sugar, and water in a large pot.

Bring to a boil slowly, stirring until sugar is completely dissolved.

Turn up the heat and bring to jelly stage quickly. (220°)

As jam thickens, stir frequently to prevent sticking. Remove from heat.

If foam as formed on top, skim it off.

Ladle hot jam into jars, leaving a 1/4 inch headspace.

Finish jars and process jam according to water bath canning instructions for 15 minutes.