Take 6 of the tomatoes. Quarter them, and place in large pot.
Bring pot to a boil.
Use potato masher to crush the tomatoes to release the juices.
Lower heat to a steady boil.
Stirring the pot frequently, continue quartering and adding the remaining tomatoes as you quarter them.
When all tomatoes are in, let the pot boil for a further 10 minutes.
Tomatoes at this point should be juicy and soft.
Remove pot from heat. Let cool a bit if desired.
Strain the tomatoes a batch at a time to remove the skins and seeds. You can do this by pressing through a sieve or strainer, or passing through a food mill.
Put strained juice into a pot.
Bring juice to a boil, then reduce heat to a medium simmer, uncovered, until sauce reaches desired thickness.
For a thin sauce, reduce volume by one-third. For a thick sauce, reduce volume by one half.
This can take hours depending on the quantity of sauce you are using. The wider the saucepan or pot you have it in, the more efficient your evaporation rate will be. Aside from that, there really is no magic bullet to date to do this.
When the sauce has reached your desired thickness, you can proceed to can it.
ACIDIFY: To each 1.5 litre (quart) jar that will hold tomatoes, first add EITHER 3 tablespoons of bottled lemon juice OR ¾ teaspoon citric acid.
SEASON (Optional): To each 1.5 litre (quart) jar, optionally add 1 ½ teaspoons of either salt OR non-bitter, non-clouding salt sub.
SEASON (Optional): Add up to 1 ½ teaspoons of dried herbs. Suggested is either all of one or a mix of the following: dried basil, dried oregano, dried thyme, or Italian seasoning. Dried marjoram would also be acceptable.
SEASON (Optional): Add a fresh, well-washed, unblemished basil leaf to each jar.
Ladle hot sauce into jars.
Leave a generous 2 cm (½ inch) headspace.
Wipe jar rims.
Put lids on.
Process in a water bath canner.
Process jars for 50 minutes; increase time as needed for your altitude.
Tomato sauce in 1.5 litre (quart) jars. www.healthycanning.com