The best apples for making pure cider vinegar are clean, ripe apples. If you use green, dirty, decayed, or over-ripe apples, your vinegar will probably not meet the lawful tests and your time and work will be wasted. Green apples have not enough sugar in them. The same is true of over-ripe apples. "But there isn't much sugar in cider vinegar," you say. No, that is true, but without sugar in the cider you wouldn't get any vinegar. If you were a chemist you could find out just how much sugar was contained in the juice of your apples. Unless the cider has 85 per cent. of sugar it will not make vinegar good enough to satisfy the requirements of the law. However, plenty is found in cider made from sound, ripe apples, and he who makes cider out of anything else deserves to fail. Expose any fruit juice to the air and it will change. We say, "Oh, that is fermented," and throw it away. But what is this ferment? Set a glass of fresh apple juice in the sun and watch it. In a few days you can actually see that some change is taking place. It is "working," as they say. The sugar is changing to alcohol; so the chemists tell us. What makes it do this? The chemists must answer again. They say that there are yeast plants in the apple juice. How did they get there? We did not put yeast in the apple juice. No, but the air is full of the spores of wild yeast plants so the juice does not have to wait till we put in domesticated yeast from a little "silver" wrapper. As these yeast plants grow they cause the sugar in the juice to change to alcohol. There are lots of other wild spores in the air and in the dirt which collects on the apples if they are left out very long. Some of these spores may be of a kind that would delay the fermentation. For this, if for no better reason, we should wash our cider apples. In a glass of cider set out in the sun it does not take long for the yeast plants to convert all the sugar to alcohol, because warmth hastens the work. In the barrel set in a cool cellar it takes longer, about six months. But you have no vinegar yet. You have nothing but "hard" cider which isn't fit for anything. But in the barrel along with the yeast plants are lots of other bacteria, to be seen under the microscope. Among them is a kind that causes alcohol to change to acetic acid. Did you ever pour off the vinegar from a jug and find a mass of jelly-like substance stopping the mouth of the jug? They called it "mother" didn't they? This mother contains great numbers of acetic acid makers and if placed in your barrels will hasten the changes that fit the hard cider for use on the table.