Bumper stickers like "I Brake for Squirrels" seem kind of dumb and passive-agressive to me but last week in Little Compton an "I Brake for Strawberries" sticker might have been useful. Fortunately, not much traffic. With six quarts of strawberries purchased road-side, it was time to make strawberry jam.
In the past I've made strawberry preserves using an old North Carolina newspaper recipe. The preserves were delicious but there were two flaws: 1), the process took two days and 2), the strawberries floated to the top of the jars. The recipe here is easier and the berries stay in place.
Begin by washing and thoroughly draining the berries and preparing the jelly jars and equipment (see Raspberry Jam rhodeislandismyoyster.blogspot.com/2010/07/raspberry-jam-easier-than-pie.html).
3 lbs strawberries*
4 cups sugar
1/4 to 1/3 cup fresh lemon juice**
* rarely is the pint or quart of strawberries you buy an accurate measurement so weighing is the best method here
** if your berries are not very ripe you can use less lemon juice but 1/3 cup is a safer bet
Put the strawberries in a wide pot and smash them a bit. You can use a potato masher or a dough blender if you have either but, in a pinch, take a strong whisk and poke it up and done several times. You aren't trying to annihilate the berries, just break them up a little.
Bring the fruit to a simmer and cook at a simmer for about ten minutes. Think almost but not quite boiling.
Add the sugar and lemon juice and stir until the sugar is dissolved. Then bring it all to a boil and cook, stirring every minute or two, for about twenty minutes. Now comes the tricky part. You can make raspberry jam by formula and the timing is always the same but with strawberries a little testing is required - my jam took twenty minutes but your jam might take only ten or fifteen minutes; much depends on the size, type and ripeness of the berries. At the ten minute mark dip a teaspoon in, take it out and hold it sideways over the pan. If the juice falls all at once into the pot, it's not ready. You are looking for the spoon to lose its coating of syrup a little slower, falling in slightly thickened drops. You can test with a candy thermometer but if you cook to the "jelly" mark on the thermometer your jam will be a thick blob of strawberry rubber, so learn the spoon method.
The moment the strawberries look ready to you, turn the heat off and ladle the jam into prepared jars, wipe the rims with a clean, damp cloth and seal. Cool on a strong rack (strong so the jars don't slide to the middle).
Do your thing with labels and Voila!
Note: If you insist on changing the proportions (want to eat less sugar, etc. etc.), you are on your own. There's a chemical balance here that makes the whole process work.