Follow steps 1 through 4 of Canning Instructions, using four pint-size jars.
Meanwhile, enclose cloves, peppercorns, allspice, celery seeds, mustard seeds, and bay leaf in a double layer of cheesecloth and tie tightly with string.
In a blender or food processor, whirl tomatoes, bell peppers, onions, and garlic, a portion at a time, until smooth. Pour purée into a 10- to 12-quart pan. Add spice bag, salt, brown sugar, and vinegar.
Measure volume (see "Sunset's Canning Tips" below). Bring to a boil over high heat, stirring occasionally. Reduce heat to medium-high and stir often until mixture is thick and reduced by 1/2 and liquid no longer separates from solids (spoon some into a small bowl to check), about 1 3/4 hours. Lift out spice bag and discard.
If desired, whirl ketchup, a portion at a time, in a blender until very smooth.
Follow steps 5 through 11 of Canning Instructions, leaving 1/8 inch of headspace in each jar and processing jars for 15 minutes (see Notes).
Sunset's Canning Tips:
Add butter to jams and jellies to prevent foam from forming during cooking. If you omit the butter, skim off the foam before ladling jam or jelly into jars. The recipe will yield about 1/4 cup less.
Measure all the sugar into a bowl before beginning the recipe. Many canning recipes call for a large volume of sugar to be added when a mixture is already boiling; measuring ahead simplifies this step and prevents mistakes.
Use a ruler to measure volume. Some recipes call for a mixture to be reduced by a certain amount. To ascertain this easily, insert a clean, wood ruler into the pan before cooking and measure how far up the mixture comes. Then cook as directed until it has reduced by the percentage specified. For example, if uncooked mixture measures 4 inches in pan and recipe says to reduce by half, cook it down to 2 inches.