Bring 8 cups of water to a boil and add 10 lbs of tomatoes, a few at a time.
Blanch the tomatoes for 30 seconds.
Drain and put tomatoes in ice water to make peeling easier. Peel and cut the tomatoes.
Put the tomatoes, three finely chopped onions, and two chopped green peppers into the same pot.
Make a spice bag with mustard and celery seed and add them to the pot.
Add all the other ingredients (brown sugar, salt, ginger, cinnamon, allspice, cloves, nutmeg, and white vinegar) and carefully mix.
Bring to a boil, occasionally stirring to prevent anything from sticking to the bottom of the pot.
Reduce heat and simmer uncovered for 60-75 minutes. Cook longer or remove earlier when the mixture has thickened.
Remove the spice bag.
Use a ladle and funnel to put the relish into sanitized canning jars. Leave about half an inch of space at the top of the jar. Too much or too little space risks breaking your canning seal.
Remove air bubbles with a knife or spatula and seal with sanitized lids.
Place jars into a boiling water canner. The water should be at least one inch over the top of your jar lids and already simmering when you add the jars.
Let jars cook for twenty minutes and carefully remove.