No, per the guidelines they are not considered safe to use. You risk broken jars, weak or no seals, wasted food, and a real mess in the canner.

You never process partially filled jars. Air remains trapped in the jar and allows bacteria growth and oxidation of the food. Fridge storage only and ASAP use.

Have you checked out all the resources provided by NCHFP including the FAQs there? Most all basic questions are covered in detail if needed.

tomatoes, chunky in their own juice

Do you mean Crushed Tomatoes? Or what? Whole or Halved packed in tomato juice or with no added liquid? Raw or hot packed? They have very different processing times. And don't forget the added lemon juice or citric acid.

Dave

Here is a link that might be useful: NCHFP

Should the 3/4 full jar be pitched now? It has been about 2 weeks since I did that one. I am doing crushed tomatoes, no added liquid, hot packed with lemon juice. Printed the recipe and keep it on the counter while working with the 'maters.

Yeah that one needs to be tossed. And disposed of with great care, preferably unopened. It has had plenty of time to turn risky. Avoiding this issue is why a specific amount of headspace is given for each recipe.

Dave

For many years, people used any jar that could seal. Personally, I've used and still use any jar that the rings will fit correctly. I realize that the jars may not be as strong, so I don't pressure can in them. I'm teaching my grandchildren to use the actual canning jars, but I'm still using some of them. More and more of my 'mayonnaise' jars are disappearing and mayonnaise doesn't come in the right jars any more.
I will eventually not have any 'non' canning jars left, but at this point I'm using them and understanding the caution.

My partial jars go in the frig and that helps to decide what's going to be for dinner the next few days.

I know I'm not 'right' in doing this, so don't give me the riot act.

I know I'm not 'right' in doing this, so don't give me the riot act.

Nah, wouldn't think of it. The mess one has to clean up when one of them breaks is lesson enough. :-) Been there, done that, got the T-shirt !

Dave

Not sure whether this tip is helpful here.

If one has a partially used jar - whether it is a cook-in sauce or a jam or almost anything either commercial or home-made, there is a way to re-seal it without it going off or becoming mouldy.

Place the partially-used jar into the microwave and run for one minute on full power. Whilst doing this, wash the lid, rinse under running water and shake off to dry. Do NOT use a drying cloth as this could add contamination..

The moment the microwaving is done - as soon as the minute is up, hold the jar with a cloth to avoid burning your fingers and screw on the top. If it is the type of top with a safety button, you will hear that ping in, creating a partial vacuum up to about ten minutes later.

By doing this, you are sterilising the top of the product and the air and it can be kept, not in a fridge, but in a cupboard and can be forgotten about until you next want to use it six months or a year later - it works and is safe every time. I've never had a recurrence of mould since using this technique.

Chris.