This recipe yields about 5 half-pints, but this varies depending on your fruit.
Here is a short glossary of basic canning terms:
Band: A metal, threaded screw band used with a lid to form a two-piece cap.
Boiling-Water Canner: A large pot or kettle big enough to completely immerse filled jars; used to process jars.
Gelling Point: Point at which a cooked soft spread sheets (rather than drops) off a spoon.
Headspace: The unfilled area between the rim of a jar and the top of the contents of that jar.
Lid: A flat, metal vacuum sealing lid used with a band to form a two-piece cap.
Preserves: A type of soft spread where the fruit retains its shape; the syrup is much thinner than a jam or jelly.
Processing: Sterilizing jars and their contents in a canner (a boiling-water canner, in our case) to destroy any bacteria or enzymes that may harm you.
Step 1: Gather Ingredients and Supplies
Gathering all of the necessary ingredients and supplies before you begin will save you time and make the canning process much smoother.
You will need the following ingredients and supplies:
5 cups (2 1/2 lbs) pitted plums)
1 cup water
4 cups sugar
large saucepot (3 quart capacity should be fine)
small saucepot (This is just to keep the lids in, so size isn't as important)
canner or large stockpot (This is what the filled jars will process in)
wooden spoon or wire whisk
jelly jars (a.k.a. half-pint jars)
lids and bands
Optional: You will need either a candy/jelly thermometer, or a saucer and a spoon (or both). This will be used to test the gelling point of your preserves.
It is very helpful to have canning utensils, such as a jar lifter, lid lifter, wide-mouth funnel, and headspace tool. However, if you do not have these, you can use tongs (to lift jars out of the hot water), a fork or a magnet (to lift lids out of the hot water). Just be very careful not to drop your jars!
Step 2: Set Up Your Workspace
Before you start canning, it is important to have your workspace set up so all of your supplies will be ready when you need them.
First, your jars and lids (don't worry about the bands) must be hot when they are filled - this is very important!
Keep your lids hot by keeping them on the stove in a small saucepot filled with simmering water. You can keep the lids simmering until you are ready for them - just do not let the water come to a hard boil, as this could damage the seal. I usually keep the pot with my lids on a back burner so they're out of the way.
You can keep your jars hot one of two ways. You can place your empty jars in your canner or stockpot with enough water to cover them by about two inches, and let this water (and the jars) boil until you are ready for them. Or, you can load your dishwasher with the jars (no other dishes at the same time, please!) and let them run through a regular or "sanitize" cycle. Your dishwasher will keep the jars hot until you are ready to use them. If you choose the dishwasher method, you should still fill your canner or stockpot with water (enough to cover jars by 2 inches) and bring the water to a boil (with the lid on) so the water is ready for processing once your jars are filled. I usually put a few more jars in my hot water bath or dishwasher than the recipe calls for, just in case I end up with more preserves than I expected (which happens frequently). For example, this recipe should make about 5 half-pints, so I'll probably have 7 jars ready, just in case (just don't forget the extra lids, too!)
Lay a towel down over your countertop. This is where you will place your jars during filling and after processing. It catches any drips, but also protects your jars.
Step 3: Prepare Your Plums
This recipe calls for the plums to be pitted before cooking. To do this, take a knife and cut a plum in half lengthwise (you'll be able to feel your knife hit the pit, and then you can simply rotate your knife or the plum until it is halved). Then, pull out the pit and throw it away.
You can choose what to do about the peels (skins) of the plums. If you don't like the skins, you can remove them by blanching*. I leave the skins on because I like the darker color they give the preserves. If you want a dark color but no skins, the skins can be removed from the saucepan right before you fill the jars - by that time, they should be separated from the meat of the fruit.
*To remove skins by blanching, bring a pot of water to a rolling boil. Lower a few (4 or 5) plums at a time into the boiling water, and leave them in for 30-45 seconds. Then, remove the plums and immediately place them into a bowl of ice water. Once they have cooled (it only takes a few seconds) the skins slide right off.
Step 4: Cook Preserves and Test Gelling Point
After you've pitted (and possibly peeled) your plums, put them in a large saucepot. Add in the water and sugar, and slowly bring the mixture to a boil, stirring to dissolve the sugar. As they heat, the plums will begin to change colors and fall apart. If this doesn't happen, you can mash them into whatever size pieces you want.
You'll need to test it for doneness by checking its gelling point. This can be done one of two ways: with a candy/jelly thermometer, or with a spoon (a "sheet" test).
To test the gelling point with a candy thermometer, first position the thermometer in boiling water (like the water your jars should be in right now!) and read it. Add 8 degrees Fahrenheit to that reading - this is your gelling point. Once you've established your gelling point, position your thermometer in the saucepot with your preserves, and watch it carefully. Continue stirring to prevent sticking, and always read the thermometer at eye level. Right before your preserves reach the gelling point temperature, remove the saucepot from the heat, and move on to step 5 (Filling the Jars).
To test the gelling point by the sheet test, place a saucer on the counter next to your saucepot, and get a cool, metal spoon. Dip the spoon (sideways - we're simply coating the spoon in the preserves, not scooping them up) into the preserves, then move the spoon over the saucer (keep it away from the steam from the saucepot). When the preserves first start boiling, they will drip off the spoon like a thin syrup. As the preserves thicken, they drop from the spoon in larger drops, and begin to show signs of sheeting. The gelling point is reached when the jelly breaks off the spoon in "sheets" (Please refer to the picture). Remove the preserves from the heat right before the gelling point is reached, and move on to step 5 (Filling the Jars)
Step 5: Fill Your Jars
Right before your preserves reach the gelling point, remove the saucepot from the heat, and immediately fill your jars. Leave 1/4 inch headspace (using a headspace tool or measuring tape).
Once your jars are filled, wipe the rims off with a damp towel to remove any drips. This is very important - if you skip this step, your seal may not form properly.
Remove lids, one at a time, from the simmering water, quickly dry off, and place on top of filled jar. Then, screw on the band (hold the lid in place with one finger in the center, and use the other hand to screw on the band).
Step 6: Process Your Preserves
Once the caps (lid+band=cap) are on your jars, place them back in the canner or stockpot filled with boiling water. You can place as many jars as will fit, but don't overcrowd them. Replace the lid of the canner or stockpot, and adjust the heat to medium high. When the water returns to a boiler, start your timer.
Process your preserves for fifteen minutes. When the processing time is over, turn off the heat, remove the lid to the canner or stockpot, and let everything sit for another five minutes. Then, using a jar lifter (or tongs) remove the jars from the canner or stockpot and place them on the towel. Make sure to leave an inch or two of space between the jars. Once you've set your jars on the towel, do not move them until after they are cool and you have checked the seals - doing so could prevent the lids from sealing properly.
Note: If the metal bands loosen during processing, it is okay! Do not re-tighten them! Don't mess with the cap at all, just to make sure everything seals properly.
Step 7: Cool Jars and Test Seals
As your jars are cooling, they should start sealing. Each time a lid seals, you will hear a popping sound. You can also tell by looking at the lids whether or not they have sealed.
After at least 12 hours (but before 24 hours) you can can test your seals. Press the center of the lid to make sure it is concave, then remove the band and (gently!) try to lift (not pry) the lid off with your fingertips. If the center doesn't flex up and down, and you can't lift the lid by gently pulling, then your jar has a good vacuum seal.
In the event that some of your jars do not seal properly, you can reprocess them. To do so, remove the band and lid and empty your preserves into a saucepot. Reheat them by bringing them up to a boil, then ladle them into a clean, hot jar as before. Place a new, hot lid on the jar (make sure you wipe the rim off!), hand-tighten the band, and process them again for the full fifteen minutes.
Step 8: Store and Enjoy
After your jars have completely cooled, label and date them. Most jelly jars come with adhesive labels, or you can make your own.
These jars can be stored at room temperature for years. They only need to be refrigerated after opening.
If you choose to give away some of your preserves, you can decorate your jar by cutting out a small square of the fabric of your choice, removing the band, laying the fabric down, and placing the band back on, or tying a ribbon or twine around the mouth of the jar.
After you've eaten your preserves, the jars and bands can be reused in future canning projects. However, you should never reuse lids - always purchase new lids (they are inexpensive) to ensure a proper seal.