@ #26 SwingCheese: Yes, you can use an additive and then do a water bath for low-acid vegetables; often that additive is vinegar (acetic acid) or lemon juice (as mentioned by several commenters above, lemon juice is a common additive for canning tomatoes).

More commonly, the jar didn’t seal because you did not wipe off the rim before placing the lid on it, or because of a defect in the rubber of the lid, or because the jar was tilted too much in taking it out of the canner and some of the jelly got under the lid before it could seal. (Rubber deteriorates with age, so if you found a box of lids your grandmother left in the back of a drawer, don’t use them for canning.)

The National Center for Home Food Preservation has a wonderful website that gives excellent info on all aspects of canning if you don’t have a Ball Blue Book. (Also a lot about freezing and dehydrating.) I’ve recently started pressure canning meats, and that site along with my canner’s manual have been great.

Lots of people have used water bath canning (as opposed to pressure canning) for low acid foods (vegetables, meats). Some of them died from botulism poisoning, but not all. It’s kind of like drunk driving: Lots of people do it and don’t kill anybody, but it’s still a really bad idea.

The problem with tomatoes is that different varieties have different levels of acidity, and not all varieties have enough. Adding lemon juice according to a tested recipe will compensate, provided it is bottled lemon juice of known acidity. The key is whether it’s a tested recipe, such as you’d find in Ball’s Blue Book or the website mentioned above.

I think some people do but it’s taking a risk for spoilage and botulism.

I’ve been canning wine jelly for years …but before you attempt any jelly you should read a little about it. Trent says to just boil it, but you kind of need to know if it is going to jell before you put it in the jars. Following his instructions (which are the ones probably in the pectin package)I’ve had jelly not jell, or be overly soft and I’ve found with wine, it doesn’t always want to jell in that time frame and additional boiling is sometimes needed. Find a book on canning or research online to see jelling tests…one is how it looks when it pours off the stirring spoon it should ‘sheet’ or ‘break’. Or place a dab on a plate and let cool. If it is jelled and no longer runny it will then jell in the jar. And if your jelly is still runny in the jar 24-48 hours after it is cooled, you can re-process it with some additional lemon juice and, pectin and sugar, which has always worked for me. But I hate having to open the jars and redo all that work! Luckily jams aren’t so touchy.

So you can make a just tomato spaghetti sauce (adding the lemon juice) and add the other veggies/meat/whatever after you open the jar.

According to the USDA guidelines and recipes for canning they only list pressure canning for spaghetti sauce (either with or without meat).

I’ve seen some recipes that add lemon juice to spaghetti sauce for water bath canning to make it more acidic. Once you start adding fresh veggies to the tomatoes (onions, garlic, mushrooms, peppers) it brings down the acid level and, again, there’s the risk of botulism if it’s not processed correctly.

I was going to echo what others said about jars that don’t seal. They can definitely be refrigerated and used that way, and you can also try re-sealing them with new lids(I did that while canning tomatoes a few years back and all was well).

This is the second time you’ve given bad info about canning (I remember a post on canning salsa where you said you could can spaghetti sauce in a water bath, which is dangerous). I’m not sure what the cause is, but you should really try to make sure your info is accurate before you post it.