How to Make Jam

I get asked this a lot: is making jam hard? People tend to assume it takes a lot of time; that every batch is unmanageably huge; that it’s scary and uses weird equipment. All this is so, so wrong. You can make jam in a skillet or saucepan in less than an hour. If you can boil water, you can make – and can – jam.

Let me explain here in detail. Readers who have been following the blog for a long time know I’ve written about this before. Nothing much has changed – it’s still a 3 step process:

  1. prepare the fruit, the jars and the lids
  2. cook the fruit into jam
  3. fill and seal the jars

Once you know how to do these things, you’ll be ready to make any kind of jam. If you want a big batch with a big result, you’ll want big pots. If you’ll be happy with a few jars, start with just a little fruit, and use smaller pots. I’ll explain the whole process using strawberries as an example, and provide notes for small batches as we go along, so if you have a small kitchen or only a quart of berries, stay with me!


a note on quantity

Make jam in small to medium batches. I never make a batch with more than 4 quarts of prepared fruit, because the quicker jam cooks, the fresher it tastes, and a large batch takes much, much longer. I’ve made jam with only 2 cups of fruit, though that, admittedly, made just one small jar for the next day’s special brunch.


STEP ONE part 1: prep the fruit

Handle the berries as gently as possible. Fill a sink or basin with cool water, add in the berries, a quart at a time. Swish them around a bit, to dislodge any sand. Pull from the water and put on towel-lined cookie sheets in a single layer.

Remove green stems and leaves. Slice berries horizontally into a large 4-cup measuring cup. Pack the berries down a little bit. For every 4 cups of berries, use 3 cups of sugar. NOTE: 2 quarts of strawberries will yield about 6 cups of packed berries, so using that 4:3 ratio, use 4 and one-half cups of sugar.

You will need a larger pot than you might think you would – when making jam, the volume of fruit and sugar will expand at least double, and as much as triple! Plan ahead, use a big pot. Wider is better than taller, because you want to encourage evaporation. For this example 2 quart batch of strawberry jam, a 4-quart pot is big enough. I have a favorite pot that I love. 

Layer the berries and sugar in a pot or kettle: fill the pot slightly less than halfway, to allow for the increase in volume when it boils. When all the berries and sugar are in place, stir until thoroughly mixed, and then let stand, covered, in a cool place (or in the refrigerator) a minimum of 2 hours and up to 12 hours, so that the sugar will draw juice out from the fruit. NOTE: I like to crush the berries when I make jam; other folks like to see intact slices or even tiny whole berries. The bigger the pieces you like in your jam, the more gently you need to stir. 


STEP ONE part 2: prep jars and lids

empty jelly jarsYou will want the jars and lids to be ready when you begin to cook the jam. You will need spanking clean jars and lids. You could put the jars through a dishwasher cycle, to have them hot and ready to use. If you’re making a small batch that will yield 5 jars or fewer, it is quicker just to boil the jars. Put clean jars in a big pot of water that will cover them completely, bring the water to a boil, and boil 10 minutes. Turn off the heat, and hold the jars in the hot water until use.

Wash the flat lids in warm soapy water, and set them aside on a clean towel. NOTE: yes, just wash them. Lids have changed! Have some clean flatweave (lint-free) dishtowels ready. Have clean screw bands ready, but it’s not necessary to heat them. Just make sure they’re not rusty or bent.


STEP TWO: cook the berries

Make sure that there is plenty of liquid in the pan before you begin to cook. Add lemon juice and a bit of butter. NOTE: for a 2 quart batch, use 1 tablespoon lemon juice and a half-teaspoon of butter.  The butter is added to the fruit to reduce foam-up, which increases the yield of jam. You can omit it if you hate the idea. Start with medium heat, and stir often at the beginning, so that no sugar will stick and burn on the bottom. Adjust the heat to bring the mixture to a violent all-over boil, and keep it there. When the color and/or texture changes, begin to check if the jam is ready.


how to tell when jam is done

As the jam cooks, the texture of the liquid will change. Spoon some of the liquid (not the pulpy fruit) and hold the spoon up above the steam. Let it drop back into the kettle from the side of the spoon. At first (see left) it is light and thin. As it thickens, one drip will thicken into two, and if you cook it more, it will sheet off the spoon in a glob (see below). For my jam, I prefer the texture somewhere between the middle and the right picture.

Courtesy of National Center for Home Food Preservation, the photo depicts the Sheet/Spoon Test in determining whether jam or jelly made without added pectin is done.

A more tactile test is the freezer test, which I call “The Wrinkle Test”. When you start to cook the jam, put a saucer or small plate in the freezer to chill. When you think the jam may be ready, put a little dab of the hot stuff on the chilled saucer, and put it back in the freezer for 1 minute. Take your jam pot off the heat while you do this so it doesn’t cook down further. When the minutes are up, check the jam: when you push at it with your fingertip, do little wrinkles show on the surface? If so, it’s ready. If not, it needs to cook a bit more.


STEP THREE part 1: fill the jars

Line up your hot sterile jars on the counter near your kettle. Put a funnel in the closest one, and ladle hot jam into the jar just past the bottom of the funnel. Generally you’ll leave one-half inch of headspace.

Be careful! That jam is boiling hot, and will act like napalm – don’t let it get on your skin. Carefully move the funnel to the next jar, and repeat, until all your jars are full. NOTE: I always prepare 1 more jar and lid than I think I’ll need, just in case. Better to have one sterile and ready, than to run out of space. If you have an odd bit left, you can put it in a bowl or custard cup, and just refrigerate it, planning to use it during the next week or so. In my house it would last about 2 days.

When all your jars are filled, wipe their rims with a clean damp cloth. Particles of food on the rim can mean that the jar won’t seal right. Cover each jar with a flat lid (rubber gasket down). Attach screw bands to each jar only until a point of resistance is met – that’s finger tight. Don’t screw them down as far as you can get them to go! 


STEP THREE part 2: seal the jars

As you start cooking your batch of jam, have your big water kettle ready, too. For a big batch of jam, 9-14 jars, you’ll need a big 20-quart kettle. For a medium batch of 5-7 jars a smaller 12 quart pot will do well. For a tiny batch, just use a deep saucepan. Fill the pot with about six inches of water, which will level out at 2 inches over the tops of the filled jars, once they are all in there. Start to heat this water while the jam cooks.

When the jars are filled and the lids and bands on, put them in this hot water one by one. A jar lifter is the perfect tool – don’t try to use tongs, and never handle a hot jar only by its lid or band; this can break the seal. Place the jars one by one in the water in the kettle, spaced evenly. The water should cover the jars by 2 inches – if it doesn’t, add more hot water until it does. Cover the canning kettle, and bring it to a rolling boil. Set a timer, the jars need to be processed in boiling water for 10 minutes. If the water stops boiling, bring it up to a boil again and re-start the timer.

After 10 minutes of boiling, remove the jars one by one from the kettle of water. Put them upright on clean dry dishtowels on your counter with 1 to 2 inches of space between each jar. Leave the bands alone! Don’t touch them, because it can interfere with the seal. Let the jars cool naturally. You will most likely hear a series of cheerful POPs as the lids snap sealed.

After the jars have cooled for 12 hours or so, test the seals. The simplest way is to press on the center of each lid. If the center of the lid does not flex up and down, the seal is complete.


canning tools

Most hardware stores, some grocery stores, and just about all Targets and Wal-Marts carry canning supplies, including jars, lids, and some great tools. Invest in a set of canning tools once, and you’ll use them for years and years. The most common utensil kit available these days comes from Ball (the jar maker) and includes a funnel for filling the jars, a lid-magnet to retrieve lids from hot water, a headspace gauge and airbubble popper, and a jar-lifter, all for about $10. I highly recommend this kit. I also love my special canning ladle, which has a large capacity and can pour in any of 3 directions. I use a silicone blossom trivet on the bottom of my pot so that water can circulate underneath the jars, though my mom used to use a clean waffle weave dishcloth for the same purpose.

2 Responses

  1. […] Process: How to Make Jam […]

  2. […] the preserves to the boil again, stirring often, and cook until it passes a jelly test. (see How to make jam for information on the jelly test). In my kitchen today, it took about 10 minutes more. Remove […]

  3. […] How to make jam  (updated) […]

  4. Thanks Maurita!! I will be reading your blog from now on!

    • I’m so glad! This may be the longest post on my blog … most of them are shorter.

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