I have entered only my own designs and hand knit items for the past 5 years. So I understand a bit about how the fair thing works.
County Extension Office
It's really helpful if you can contact your local county extension office and even go in for a visit. I have lived in 3 different county in the last 5 years and I always go to visit the new office. They are a good resource for livestock and poultry, gardening and diagnosing garden pests ad blights, canning, etc. Everyone I have met has been very nice and truly wanting to help.
They will be the ones responsible for the entries and the judging at your fair. They may not actually take in the entries or do the judging but they will organize it. They also should have some information about canning and preserving.
I would ask if they have a copy of last years Fair brochure for you to see. It will list all of the catagories that you can enter. This will help you to decide when you are canning which things you would like to enter. You may also discover catagories for other hobbies that you might like to enter.
You can ask if they have a list of the things the judges will be looking for durin the judging. I have not ask for this yet but I plan to do so very soon.
I am a professional knitwear designer so I know the types of things that the judges 'should' look for when judging the knitting and crochet catagories. Notice I said 'should.' Sometimes they get judges who really don't know what to look for in well prepared items. They just pick things they like and that look good. It's not always fair but I still enter.
I think I am going to do a search online to see if I can find a list of things that judges should be looking for with home canned entries. I want to have a fair chance of placing and the best way is to find out what elements most fair judges would look for. And what things are the no no's.
Off of the top of my head, I can think of a few things I heard people talking about at last years fair.
1. Good color of contents
2. Correct head spacing
3. Good ratio of liquid to contents
I don't think the judges at the fairs that I have entered opened any of the canned jars. I'm pretty sure that they just go by what they can observe about the jar and contents.
I hope this helps. Maybe someone else with more Fair experience with canning entries will post and give us more information.
Good Luck to you and I hope that you do enter things in your county fair. It is great fun to do. It makes going to the fair so much more exciting. I can hardly wait to get there and see if I placed in any of the catagories that I have entered. Any place/ribbon is exciting but if you pull off a blue ribbon or a best in show so much the better. It is so fun to walk around and see all of the other wonderful things that people have done and you can glean great ideas from them.
Well...maybe they didn't come in as a link but at least you can copy and past the urls and get to the pages.
I think our extension offices should be able to give us some info that will help too.
Please let me know what you have decided to hopefully enter as you are canning. Then we for sure have to list what we entered when the Fair time comes and then post if we place at all.