Homemade jam is easy to make, easy to store, and very tasty, but sometimes the consistency is too thick or too thin. It is very easy to fix the consistency while you are making the jam, but if you complete your canning before you realize that the jam is too, then you will have to re-can it in order to thicken it.

Things You'll Need


Thickening Jam While Making It

Follow the recipe for the jam you are attempting to make. You can find quantities for the different common jams written on a flyer inside most brands of commercial pectin. These recipes are also available in reference works like the “Ball Blue Book of Canning,” the USDA website and state agricultural extension offices.

Place a measured amount of fruit, pectin, any spices, and an optional teaspoon of light oil such as canola oil in a large saucepan. Bring to a boil over medium heat.

Add your measured amount of sugar and boil for at least two minutes. Reduce the heat if the jam begins to froth or boil over.

Boil the jam gently, stirring constantly until one of the two tests indicates that the jam is thick enough to set properly. Note that extended boiling will destroy some of the fresh fruit flavor of the jam but will add caramel flavor and give a thicker, smoother tongue feel.

Perform the sheeting test by stirring the jam and then holding your stirring spoon sideways above the jam pot so that the content of the spoon will run from the side of the spoon. If jam falls in vertical drips, like water from a spoon, then it is too thin and will not set. If it jam falls in a wide blob, the width of two or three of the original streams, then the jam will set. The wider the blob, the harder the jam will set.

Perform the freezer test by pouring a spoonful of jam onto a clean plate. Place the plate in the freezer for 30 seconds. Remove the plate and press a finger along the pate and into the edge of the jam blob. If the jam is thick enough to set it will wrinkle up in little folds. If it is not yet thick enough then the jam will smear without having the top of the jam wrinkle. The thicker the wrinkles, the harder the jam will set.

Can the jam in a boiling water canner following the instructions on the pectin package or the instructions below.

Thickening Jam After Initial Canning

Open all the jars of canned jam that you want to thicken and pour all the jam into a large saucepan. Discard the old lids. Wash and sterilize the old jars. Prepare canning jars and new lids.

Heat the jam over medium heat until it reaches a steady boil while it is being stirred. Continue to boil the jam until it passes one of the thickening tests.

Perform the sheeting test by stirring the jam and then holding your stirring spoon sideways above the jam pot so that the content of the spoon will run from the side of the spoon. If jam falls in vertical drips, like water from a spoon, then it is too thin and will not set. If jam falls from the spoon in a wide blob the width of two or three of the original streams, then the jam will set. The wider the blob, the harder the jam will set.

Perform the freezer test by pouring a spoonful of jam onto a clean plate. Place the plate in the freezer for 30 seconds. Remove the plate and press a finger along the pate and into the edge of the jam blob. If the jam is thick enough to set it will wrinkle up in little folds. If it is not yet thick enough then the jam will smear without having the top of the jam wrinkle. The thicker the wrinkles, the harder the jam will set.

Boil the jam gently, stirring constantly until one of the two tests indicates that the jam is thick enough to set properly. Note that extended boiling will destroy some of the fresh fruit flavor of the jam but will add caramel flavor and give a thicker, smoother tongue feel.

Filling and Sealing Jam Jars

Sterilize your jars and rings by washing them carefully and then boiling them in canning kettle for ten minutes. Turn off the heat and then add the new lids to the canning kettle. This step can be done before you boil the jam. Once the jam is ready to be canned, use tongs to remove glass jars from the boiling water canning kettle and line them up next to the jam kettle.

Use a ladle and optionally a large funnel to fill the hot jam jars. Leave an inch of head-space at the top of each jar. One hint is that pint jars normally pinch inward at the right spot for head-space, while engraved jelly jars have the engraving stop at about the right spot for head-space. Overfilled jars will not seal properly.

Wipe the top of each jar with a clean new paper towel to remove any drips or spills that might interfere with the seal. Place the warm canning lids on the top of the glass jars. Place a finger on the center of each lid to hold it lid in place while you attach the ring to the jar. Do not tighten the rings: you need to let heated air escape from the head-space.

Place the jars into the canning kettle with the jar lifter or tongs. Add water if necessary so that the water level is at least one inch above the top of the tallest jar. Bring the canning kettle to the boil and boil for ten minutes or for the time specified by the recipe you are using. Longer boiling will reduce the fruit flavor but add some caramel flavor.

Remove the jars from the boiling water using a jar lifter or tongs and place on a cooling rack. Let the jars cool fully before touching them. You should hear a “pop” sound from each jar as the vacuum created by the cooling head-space sucks the lid onto the jar to create a firm seal.Test each jar by pressing down on the center of the lid after the jar has cooled. If the jar sealed properly then the lid will be in the down position and you will not hear anything. If the canning failed then you will hear a pop sound and will be able to press the dome of the lid down. Refrigerate jars that did not seal properly. Eat these first. Label properly sealed jars with their contents and the date and store them for up to five years.