Put the figs in a large stockpot. Sprinkle them with the baking soda and cover with the boiling water. Allow the mixture to stand 15 minutes, then drain and rinse figs in three changes of cold water and drain.
Combine the three quarts of water and the four pounds of sugar in a large stockpot. Bring to a boil and stir to dissolve the sugar. Cook for 10 minutes. Every few minutes, skim the foam that forms on the surface and discard. Gradually add the well-drained figs to the boiling mixture, taking care to keep the mixture boiling. Continue boiling the figs until the fruit is tender and transparent, about 2 hours. Remove the figs from the boiling liquid with a slotted spoon and place in shallow pans. Continue cooking the syrup until it is the consistency of honey, then pour the syrup over the figs making sure that the figs are entirely covered with the syrup. Let the figs stand overnight.
Pack the cold figs, stems up, in sterilized pint jars. Fill each jar with syrup leaving 1/4-inch headspace. Seal the jars with two-piece metal screw down lids and process in boiling water 15 minutes (see water bath processing below). Tighten seal completely and cool.
Water Bath Processing for Figs
Fill a water-bath canner with about 6 inches of water. For cold figs, heat water to very hot but not boiling. Arrange filled jars in the canner slightly apart and cover jars with at least 1 inch of water. Bring water to a gentle boil and begin timing. Boil 15 minutes, remove jars, and cool.
Makes about 12 pints