Mike Cordova, age 9, of Santa Rosa, California for his question

How do they make vinegar?

This job takes us down, down to the world of tiny tiny things that are too small for our eyes to see. Some are teeming atoms and molecules. Some are midget living things called molds and yeasts and bacteria. We put the right ingredients together and just let these tiny things change them into tangy tasting vinegar.

Making vinegar is a chemical process somewhat like the cooking process that changes tacky dough into spongy, sliceable bread. The process is fermentation and we say that word as if it were spelled "fur men tay shun". This fascinating fermentation is happening all around us and the wonderful world of growing things could not get along without it. It happens when certain busy chemicals get together and change each other into chemicals that are quite different. We can see, smell and taste the results of fermentations. But because chemicals are made of atoms and molecules, we cannot actually see these tiny workers perform their magic changes.

Some fermentations are caused by chemicals called enzymes. There are enzymes in your stomach to change your food so that its nourishing chemicals can be dissolved and carried around by your blood stream. Some fermentations are triggered by yeasts, molds and bacteria. To see these living midgets we must enlarge them under a microscope. We need yeasts to ferment tacky dough into digestible bread. We need bacteria to change milk into cheese and buttermilk. We need other bacteria to make vinegars from apples or grapes, melons or molasses, berries or cereal grains.

The homesteading pioneers made their vinegar and their soap right out in the back yard. To make vinegar, they started with a big oak barrel of fruit, grain or molasses and water. Then they let the natural process of fermentation take its time. The vinegar was ready in one or two years. The pioneers did not know that the fermentation was triggered by tiny bacteria. Or that the ingredients in the barrel always teem with assorted bacteria    and some were the right ones to make vinegar. If they had known these things, they could have helped the bacteria to ferment faster. Our clever chemists have shown us how to change a tank of ingredients into vinegar in a couple of days or so.

A modern factory has whirling electric generators that can turn out 1,000 or 2,000 gallons of vinegar in a few days. The busy bacteria need warmth and lots of moist air. So the warmed liquid ingredients are whirled through corncobs, cindery coke or other spongy materials that are riddled with pockets of air. The busy bacteria ferment fast, changing surgary chemicals into alcohol and bubbles of carbon dioxide gas. Then the mixture is sprayed out in drops. The gassy bubbles go off and mix with the air. And the air changes the alcohol into a chemical called acetic acid. Plain white vinegar is just plain acetic acid. Apples in the mixture add the fruity flavor to cider vinegar, grapes give us sour wine vinegar and cereals add the dark color and rich flavor to malt vinegar.

Most of plain white vinegar is made from watery molasses or the liquids from curdled milk. First the busy bacteria ferment and the brew is changed into strongly flavored vinegar. Then the vinegar is boiled and the rising steam is trapped in pipes. It is led away and cooled back into drops of liquid. This is called distilling. It separates the basic liquid and leaves the flavors, colors and other chemicals behind. The distilled vinegar is just plain acetic acid that has its own sour sharp taste with no added color or fruity flavors.