Glasses of jam and sweet preserves, looking like jewels in jars, offer a way to take summer's surplus, cook it down to its essence and store it away, in neat packages, to brighten even the bleakest days of winter.

Homemade preserves make good use of any fruit harvest. They taste better than commercial products, and, because you've made them, there's great satisfaction in serving them. Homemade jams can transform buttered bread into a rare and delicious treat.

Jams couldn't be simpler to make. It's only jellies that need careful balancing of acid, sugar and pectin. Jam is more free-form. In a jam session you can take all kinds of fruits and combine them into delicious preserves.

I used to think jam had to be made according to rules, which usually call for equal amounts of fruit and sugar, but a World War II canning book put me wise. The wartime canners had to make low-sugar preserves and jams with honey. Their tales inspired me to start experimenting with fruits and combinations.

The jams I make now usually include a quarter as much honey as fruit, and they'll work with even less sweetening. They make less jam than the equal-sugar recipes, but they taste much fresher. The jam has to be processed in a water bath, though, because it's more like a sweetened fruit puree and it doesn't have enough sugar to preserve it without processing.

It will be like fruit butter with chunks, or old-fashioned preserves. I've used this method for peaches, plums, pears, apples, berries, cherries and combinations of fruits.

Wash the fruit and slice it if necessary. You have to peel apples and pears for jam, but not for fruit butter - you can just blend the fruits with the skins. I peel peaches, but not plums, and slice everthing but berries.

Measure the fruit as you slice it, and remember how much you have. For each quart, you'll need a half to a whole cup of honey, depending on how sweet you like your jam. Put the fruit into a large enamel or stainless kettle and mash it until you get some juice.

Simmer the fruit, stirring and mashing from time to time, until you have a thick puree that's as chunky as you like it. You can blend some, or run it through a food mill, to make a smoother product.

The consistency, as well as combinations and spices, is where you have to do your own jamming. It's your choice. But don't add the honey too soon or it will make the juices flow.

If you like the fruit puree, you can sweeten it lightly and put it up as a fruit sauce. Just pack it into clean, hot jars and process them in a water bath - 20 minutes for quarts and 15 minutes for pints. To jam it, you'll have to do more cooking.

Once the fruit mixture is thick you can add the honey - half a cup to a whole one for each quart of fruit you started with - and watch the mixture juice a little. Cook it over medium heat, stirring so it doesn't stick, until it's thick and a little bit dropped on a cold plate holds together.

Pack the jam into clean half-pint or pint jars, seal and put into a boiling water bath for 10 minutes on pints and five minutes on half-pints. Let the jars cool and label them.

If you combined fruits, note the combinations so that when you come up with a smashing success you can try to duplicate it next year.

And don't be bound by your ordinary conceptions of jam. Consider old-time fruit conserves, which included nuts, bits of candied fruit peels, raisins and all kinds of spice.

Try anything you can imagine. Let your fancies carry you beyond the borders of the ordinary. Some of your jam sessions will undoubtedly turn up new and original symphonies of summer. And they'll delight you long after summer has become another memory.