Muscadine Jam

Prepare the grapes by thoroughly washing and draining them, then use a sharp paring knife to slice each muscadine in half and remove the tough skins and any seeds.
Combine the prepared grape pulp, sugar, and lemon juice in a large, heavy-bottomed pot or Dutch oven, stirring everything together until the sugar is mostly dissolved.
Bring the mixture to a full, rolling boil over medium-high heat, stirring frequently to prevent sticking, then stir in the 1/2 teaspoon of butter to help reduce foam.
Continue cooking the jam at a steady boil, stirring constantly, until it thickens and reaches the gel stage, which should take about 20-25 minutes; a good test is when the jam sheets off a cold metal spoon or reaches 220°F on a candy thermometer.
While the jam cooks, prepare your canning jars and lids by washing them in hot, soapy water and keeping them hot, then carefully ladle the finished hot jam into the hot sterilized jars, leaving 1/4 inch of headspace.
Wipe the rims of the jars clean with a damp cloth, apply the lids and rings, and process the jars in a boiling water bath for 10 minutes to seal them properly.