Canning 101: Why You Shouldn’t Double Batches of Jam

jam bubbles

If you’ve been canning for any length of time, one of the warnings you’ve probably heard is that you shouldn’t double jam recipes. However, no one ever really explains why it’s not a good idea. Let’s change that, shall we?

First off, it’s not recommended practice because if you double the amount of jam in the pot, it just won’t cook as well or effectively. Most jam recipes already call for you to use the widest pot you have, for maximum surface area. This large surface area leads to faster evaporation of water. Fast cooking leads to the freshest tasting, best textured jam.

However, if you double the amount of jam in your pot, you greatly increase the cooking time, because there’s so much more product in the pot that needs to be cooked down. This can lead to rubbery batches, burning and jam that doesn’t set. It can also as much as double the amount of time you spend cooking the jam.

It’s far better to make two smaller batches than it would be to try and double a recipe (unless you have an industrial stove and an absolutely massive pot).

Big thanks to Susie for her email, which made me realize I’d never addressed this issue.

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60 Responses to Canning 101: Why You Shouldn’t Double Batches of Jam

  1. 1
    Lu says:

    Another problem with doubling is that all the jars you obtain probably won’t fit into you canner!

    Though the few times I’ve doubled recipes it’s worked fine as look as I:
    1. Used pectin (Pomona for me). It won’t set otherwise
    2. Watch it very carefully as it cooks and stir more often
    3. Either use a regular pot as canner number 2, or don’t bother sealing half of the jars and just give them out as gifts for immediate consumption :-)

  2. 2
    amy says:

    Great info!! I had heard not to double any recipe for canning,( like brine for pickles etc) but I really couldn’t figure out why, and I have lately been “jamming” it up in the kitchen and I did double a few jellys and jams. My cooking time was very long. Luckly they turned out, but I agree that small batches is a better idea. Thanks again, it is so nice to have these important tips for early canners like me:)

  3. 3
    meemsnyc says:

    Thanks for the explanation. I’ve wondered that!

  4. 4
    Saille says:

    I think is really depends on whether you use pectin or not, and which pectin you use. Using commercial pectin vastly reduces the cooking time already. The directions on Pomona pectin (calcium triggered) specifically say “double away”, and I’ve had nothing but success doubling my recipes using it. Ball/Kerr pectin (sugar triggered) specifically says “do not double”. If I was going old-school and pectin free, I would not double. Longer cooking times produce a different looking end result, in the very least.

    In the end, there’s rather an art to it, if you go off-recipe. Knowing the science behind the preservation is a good start.

  5. 5
    Rebecita says:

    Yes, thanks for spelling that out! I also use pomona’s pectin, which promises truthfully that you can double freely, but I always wonder about those dire warnings…

  6. 6
    Heather says:

    I thank you and Susie. I am planning to can for the first time this year and I didn’t know about this. Whew!

  7. 7
    Bridget says:

    I love to be efficient, and so OF COURSE I tried doubling up. It wasn’t terrible, but was not a very firm set, and the fruit cooked more so it was a little darker than normal. Not bad, actually good!, but not perfect.

  8. 8
    Susan says:

    Thanks for this explanation and answering the question I have always had “But Why?”. We so often forget that there is actually quite reasonable rationales for the things we do without even thinking.

  9. 9

    I was just thinking about this… I made a marmalade that called for 2 grapefruit, but I used 2.5 since I had a half for breakfast. Between that and not having a huge pan, it took FOREVER to set. And then when I thought it had, and canned it, it was still goopy, so I had to open all the jars and re-do it. On the plus side, it tastes delicious.

  10. 10
    Brooke - in Oregon says:

    Thanks once again for giving us more detail in the HOW TO and WHY! :)

  11. 11
    Sandi Garcia says:

    Okay then — that explains why my first attempt at marmalade is a bit iffy although I used the Blue Chair grapefruit-lemon recipe and followed it to the letter, but I’ve got to think that this would be considered a double batch. I used the large copper jam pan and was a bit anxious that it would not be large enough — it was, but it took FOREVER to cook down and while it set it is very solid and I guess rubbery is a good word — it has a wonderful deep pinkish-orange color. It gave me 12 jars and a little bit to taste. It is definitely grapefruit and VERY tart to boot. I should have cooked in 2 batches, but I was just following orders. While we are on this subject — can it be fixed? I have read empty the jars out, add water to thin, reheat and reprocess. Could I add a bit more sugar at this time as well? I would love to hear any remedies as I sure don’t want to toss out 3 days work. I’ve even read where adding a bit of whiskey just before processing would be a help. Any ideas would be welcome.

  12. 12
    Catherine says:

    I’m echoing Lu’s comments above: not much sense in doubling a recipe if you have to wait to can it in two batches. Then you’re dealing with keeping half of the batch warm (and bringing it to a boil again) while the 2nd batch is in the canner. If you’re making multiple batches, the most efficient way to do it is to prep the fruit all at once but measure it out in separate bowls, one for each batch. Cook one batch and while it’s in the canner you can get the next batch right into the pot to start cooking down. That keeps the process moving along and gives you time to wash dishes in between.

  13. 13
    Evalyn says:

    I’m happy to know that. Previously, my only explanation was: “that’s what my mother told me.” Since I turned 61 this years, it’s nice to have a different sort of explanation.

  14. 14
    Granola Girl says:

    Oooh! so that is why the blackberry jam didn’t set this year. Thanks for the info.

  15. 15
    Kathleen says:

    Thanks for that explanation. It makes so much sense when you think about it!

  16. 16
    Arlene says:

    I have to admit that I am one of those that will double a recipe and not think much about it, but to be fair, I do have huge cooking pots, including some that take two burners per steel pot and that I have second stove that gets cracked out for the summer kitchen and to help with canning/fall processing.

    The house stove is a electic and my “summer stove” covered on the deck just off the kitchen is propane and I also have a small wood stove outside for maple syrup time..

    I like small batches for some things, but for others, I like the old fashion darker/richer flavors that slow simmers for a long time give.

  17. 17
    Jewel says:

    Well THAT’s why my quadrupled batch of strawberry balsamic jam didn’t set! Luckily it it is still delicious- thanks for spelling it out for those of us who avoid commercial pectin!

  18. 18

    [...] Marisa @ Food In Jars has another wonderful canning tutorial: Why you can’t double that jam recipe. [...]

  19. 19
    Jaclyn says:

    Now that you’ve posted this, its got me thinking about the opposite. This upcoming growing season will be my first time doing jams and preserves. I was planning on doing a few half batches of recipes to have a nice variety and not be totally overloaded with jams. Is it ok to cut recipes in half?

    • 19.1
      Marisa says:

      In most cases, it’s perfectly fine to cut recipes in half. Just keep in mind that the cooking time might be a bit shorter than called for in the recipe, because you don’t have as much volume in the pot.

  20. 20

    Thanks so much for this article! I’ve always wondered why you’re not supposed to – and also wondered why when I DID ANYWAY the jam came out wrong. Now I get it!

  21. 21

    [...] loss of quality.  With few exceptions, jams and jellies do not multiply well when cooking as Marissa at Food in Jars explains (I won’t steal her post – be sure to check it out as she’s [...]

  22. 22

    [...] more with no-pectin-added jams, so I tried this recipe.  I committed a jam-making sin and doubled the recipe, but it didn’t seem to do any harm, although the cooking time was longer.  I was really [...]

  23. 23

    [...] four pints of strawberries.  I was doing two batches, but it’s important when making jam not to simply double a recipe… unless you are super comfortable canning or you have a really wide pot, you’ll find [...]

  24. 24

    [...] off, it’s not recommended practice because if you double the amount of jam in the pot, it just won’t cook as well or [...]

  25. 25
    Marmalade says:

    Thank you for posting, I cant count the times Ive wondered about this very topic!

  26. 26
    Hillary says:

    Doubling can be done with a little bit of practice and a large copper pot. The trick is in simmering the fruit in the sugar for a moment and letting it macerate in the refrigerator overnight. The following day, turn the mixture into a sieve and boil the juices and sugar alone until they begin to jelly, and then add the fruit and proceed as usual. (Very important with this method, do not stir the boiling syrup or the mixture will candy.) I do not use commercial pectin, have “Mes Confiture” by Christine Ferber for a recipe guide, and I always use the inversion method to seal the jars.

    Incidentally, thank you Food in Jars for the recommendation of “Putting Up” and “Putting Up More”. They have opened the door to heritage pickling recipes in a way that I did not think possible.

  27. 27
    Leslie says:

    I am new to canning (just made my first batch of strawberry jam earlier this evening) and am wondering about a couple things.

    1. Can I use less sugar than indicated in the recipe or will that affect how the jam sets up? I had a bit of extra jam and while it was very good it tasted very sweet (at least when I licked my fingers).
    2. If the recipe says to expect about eight half-pints, could I make four pints instead? Would that affect the processing time? How much headroom would need to be left in the pint jar?

    Many thanks for your guidance!

    • 27.1
      marisa says:

      Leslie, reducing the sugar will effect the set if you’re working with a traditional jam recipe (which most of my are). If you’re really interested in reducing sugar amounts, I recommend that you look into Pomona Pectin. It allows you to reduce the sugar and still have the jam set up.

      You can certainly make 4 pints instead of 8 half pints. Jams and jellies get between 1/4 and 1/2 inch headspace, no matter the size of the jar.

      • Leslie says:

        Excellent. Thanks so much for the quick and very informative reply. LOVE your blog. Sorry I missed you at Linvilla over the weekend. I know they cancelled the Peach Festival because of the extreme heat.

        • marisa says:

          I was bummed that they canceled the festival, but it would have been crazy to have gotten lots of people out in that heat.

  28. 28
    Jan says:

    Thank you for that information. I had heard many years ago that you cannot make two batches of jam at the same time. I just never knew why.

  29. 29
    Liz St. says:

    I was going to have some friends over tomorrow to can a few recipes. One of the recipes only yields 4 half pints and all the others yield 8. So naturally I was going to double the one that yields 4…does that mean that I really cant do that? But you mentioned doing one batch, then the other. One of the gals is bringing the fruit already prepared…should we only cook half, can that and cook the other half? But all 8 could fit in the canner…Im confused! Also, are you not allowed to fill say 10 jars, process 8 of them for the 10 minutes and then process the others? Can they not sit on the counter, waiting to get processed? Sorry for so many questions! Just beginning this summer and I thought I was doing everything right :(

    • 29.1
      marisa says:

      Liz, without seeing the recipe, I can’t tell you whether you’ll be able to get good results from doubling the recipe that only yields four half pints. If it uses conventional pectin (as opposed to depending solely on temperature to achieve set) you might be okay to double it. This post was more referencing risks in doubling already-large batches.

      As far as the serial processing that you brought up, yes, it can be done. When I end up doing something like that, I tend to lengthen the second processing time a little bit to compensate for the fact that the jars sat out for a few minutes.

      • Liz St. says:

        Thank you so much for responding! Hopefully we will be okay…the recipe is for rosemary peach jam but I think we are all planning on using it on top of meat so if it doesnt set perfect, it will be ok :) We are also making strawberry lemon, strawberry jalapeno and jalapeno…we will be busy but it should be fun!

  30. 30
    lora says:

    For whatever it’s worth, I am a new canner and I have doubled batches many times (even tripled) and only had a problem once, when I had to cook a pear-vanilla jam much longer than was stated. I use Pomona pectin exclusively and I do have a large, broad jamming pot.

  31. 31
    Julie says:

    Boy I wish I would’ve read this a couple weeks ago! I’m relatively new to canning and just discovered your sight in June. I made my first jame – a blueberry ginger recipe I think I got from you! Well, it was two make a couple nice bottles but I thought I could knock out about 8 so I quadrupled the recipe. Duh! Why change things when you’re trying it for the firs time? Needless to say my quick Saturday afternoon project left me in the kitchen all evening . . . cooking blueberries! It turned out delicious but what a chore and what a mess! Next time I will do individual batches . . . that’s my new canning mantra . . . follow the recipe and the good advice. Thank you for the great tips – I’m really enjoying being notifed about your updates on Facebook!

  32. 32

    [...] has a great post about why you should not double jam [...]

  33. 33

    [...] We’ve used the Complete Book of Small Batch Preserving,  by authors Ellie Topp and Margaret Howard, a lot this season (a lot) because we love how each and everything we’ve tried turns out.  The only thing we’d have to say is the recipes yield only a handful of jars at a time.  For many, this works well because it allows you to try something new on a small-scale to determine if you really like it.  While, for others (like us), they are too SMALL.  We hate seeing a half full water bath canner.  So, we often double, triple, and sometimes quadruple the recipes.  While, you’ve probably heard warnings against double batching because it will compromise cooking times, throw off consistency, and leave you with a poor tasting product; we are here to assure you this is not the case for the salsa and chili sauces from this book.  In fact, the cooking times were not increased and we can assure you the consistency and taste was spot on each time.  Where you should be careful not to double batch recipes is when making jams and jellies.  Food in Jars explains why in this post. [...]

  34. 34

    [...] has a great post about why you should not double jam [...]

  35. 35
    Angela says:

    I appreciate the comments about double batching issues. However, is there an answer as to why when a recipe is mixed and cooked in the SAME process and the entire mixture is cooked to 220 (single or double batches), it does not set? The pot is 7-12qt in size. Why is it that when you are cooking to a specific temperature rather than only cooking a specific time (ie 1 min most typically with single bathes – i understand the evaporation and quick cooking issue with that method versus cooking to a certain temp) it should react differently? For example, a common method is to combine your powdered pectin to your fruit, just before the mixture boils, add the sugar and then cook to 220. remove from heat and pour, seal and process. Why would this method be different for a single, double or triple batch? I just don’t understand. Please help.

  36. 36
    Amber says:

    What about non-jam/jelly recipes? Is the general rule of thumb just that you can not double any recipes for canning? I’d like to try making spiced honey for instance, and the recipe makes only 3 8 oz jars. I would like to double it but I’m not sure if it will turn out as it should or not. Ingredients are honey, lemon slices, cloves, and cinnamon sticks. Now I’m wondering about everything though – stocks, meats, vegies, fruits – can they be doubled?
    Thank you SO much!!!

    • 36.1
      Marisa says:

      The no-double-batches rule really only applies to jams and jellies. Anything that doesn’t need to achieve set is okay for doubling. Your honey should double just fine.

  37. 37
    Emily Davis says:

    This explains a lot to me.
    Apparently I need a big batch preserving book for jams. lol
    Hugs,
    emily

  38. 38
    Debbi says:

    So if it doesn’t set can within 24 hours can you pour it back in a pot and cook it again or should you just pour it and try again?

  39. 39
    Wanda says:

    I don’t double but often x 7 recipes.
    They always turn out and I just keep warm
    And reboil prior to canning second batch
    I find I can use low sugar recipes and
    This way only need 1/4 of the pectin required
    If I did 7 separate batches

  40. 40
    Nancy says:

    You said that it was OK to cut a recipe in half, I think. And there were some questions about recipes that sounded very small to begin with.

    I was wondering, if those very small recipes had already been cut in half to make a small batch, would it work to double them, becuase then you would really be restoring it to a “normal” size recipe?

    I know it’s probably impossible to say without knowing the recipe. I tried this last night with a recipe that said it was going to produce 4 cups. I should have questioned that output based on the amount of ingredients. It turned out to be a typo, and should have said 4 pints, so when I doubled it I ended up with 4 quarts of blackberry syrup, instead of blackberry preserves.

  41. 41
    Linda says:

    I need advice about Pear Jam, Most of the recipes that I see on line are mostly pears, sugar, water and lemon juice with NO PECTIN… I like my jam with “Small Spreadable chunks” so I have to cook it between 30 to 60 minutes. Some web site state that Pectin must be used with Pears??? I am confused….if pectin needs to be used with pear jam then why are there so many recipes for pear jams WITHOUT the use of pectin.
    Will pear jam sit with or without the use of pectin???? Very confusing information out there on the web. What is your opinion? to use or not to use pectin with pear jam???
    Recipe I am look at is approx. 8 cups pears, 4 cups sugar, little bit of water and small amount of lemon juice. How much pectin would I need to use IF I NEED TO USE PECTIN AT ALL???
    Thanks

    • 41.1
      Marisa says:

      Linda, pear jam can be made with or without additional pectin. However, pears are fairly low in pectin naturally, so if you cook them into jam without added pectin, the resulting jam is going to have a softer set than it would if you used commercial pectin. But either way is safe. If you want to use pectin in the recipe you’re quoting, there are a couple of ways you could go. You could whisk 3-4 tablespoons of pectin into the sugar before you combine it with the fruit. You could add two packets of liquid pectin towards the end of cooking. Or, you could use Pomona’s Pectin for a lower sugar version. In that case, follow the directions on the packet.

      Just one more thing. I don’t recommend adding water to the fruit before cooking. When you make jam, you’re trying to cook as much of the water out of the fruit as possible. When you add water, you increase the cooking time unnecessarily. Instead, stir the sugar into the fruit prior to applying heat. The sugar will help the fruit release its juice and you’ll have enough liquid to cook without anything additional.

      • Linda says:

        Ok, so if I cook my very small chunks of pears until I think they are “soft” enough I would add the “liquid pectin” just prior to removing the pears from the heat? Should I let the pear cook maybe a minute longer after adding the pectin?
        Ok, NO water….got it…
        I think I understand that since I have to cook the pears for a pretty long time to get them soft enough …for me….LOL, like I said I like small chunks but I like for it to be spreadable.
        Correct me if I am wrong, I “would NOT” add powder pectin with the sugar while cooking because I have to cook the pears soooo long to satisfy me…..lol

        Thanks for your help and advice,

        • Marisa says:

          Linda, you need to boil the pears for at least a couple of minutes after adding the liquid pectin, to activate it. No matter what set you’re shooting for, if you use powdered pectin, it should go in at the beginning of cooking.

          • Linda says:

            Hey Marisa,
            I don’t want to keep bothering you but what would you do if you wanted pear jam without a bunch of extra spices, just plain pears and sugar, maybe spoon full of lemon juice, pat of butter to keep from foaming? ( with or without pectin, liquid or power pectin)
            If you had to make a recipe to get the kind of jam, tad chunky, smooth but spreadable, how would you make it?
            There are so many recipes out there and all of them uses extra spices. I just want a clean, tasteful pear jam.
            Thanks
            Linda

            • Marisa says:

              Linda, I would just combine the fruit, sugar and lemon juice (I don’t do the butter pat thing, but you certainly can) and cook it until it’s thick enough to your liking. I don’t have the time to write you a recipe for this. Use your judgment.

        • Bettie Waddle says:

          When I made pear jam, only 2 pints, I added about 1 cup of applesauce. It didn’t really affect the taste, and I didn’t have to use very much pectin.

  42. 42
    Sharon says:

    This morning it occurred to me that maple jelly would be more convenient in some cases instead of maple syrup. I found two recipes, one with pectin and the other with carrageenan. The second recipe said that pectin would not work with maple syrup. Is that true?

  43. 43
    Sandi says:

    I don’t want to double a recipe, but I would like to use points instead of half pints. How can I do this?

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