I received several gallons of freshly-drawn maple sap from Northampton, Warner, and Canterbury, and made analyses of each lot, separating the acids, salts, and the sugar. I also analysed the sap of the yellow and white birch, which do not give any crystallisable sugar, but an astringent molasses.
I shall now communicate to you the process by which I manufactured sugar maple sap, received from the Shakers of Canterbury, who collected it with care in a clear glass demijohn, and sent it forthwith, so that it came to me without any change of composition, the weather being cold at the time. The evaporation was carried on in glass vessels until the sap was reduced to about one-eighth its original bulk, and then it was treated with a sufficient quantity of clear lime-water to render it neutral, and the evaporation was completed in a shallow porcelain basin. The result was, that a beautiful yellow granular sugar was obtained, from which not a single drop of molasses drained, and it did not deliquesce by exposure to the air. Another lot of the sap, reduced to sugar without lime-water, granulated, but not so well, was sour to the taste, deliquesced by exposure, and gave a considerable quantity of molasses.
Having studied the nature of the peculiar acid of the maple, I found that its combinations with lime were excessively soluble in alcohol, so that the yellow sugar first described could be rendered white in a few minutes, by placing it in an inverted cone open at the bottom, and pouring a fresh quantity of alcohol upon it, and allowing it to filtrate through the sugar. The whitened sugar was then taken and re-dissolved in boiling water and crystallised, by which all the alcoholic flavour was entirely removed, and a perfectly fine crystallised and pure sugar resulted. Now, in the large way, I advise the following method of manufacturing maple sugar. Obtain several large copper or brass kettles, and set them up in a row, either by tripods with iron rings, or by hanging them on a cross-bar; clean them well, then collect the sap in buckets, if possible, so that but little rain-water will be mixed with the sap, and take care not to have any dead leaves in it. For every gallon of the maple sap add one measured ounce of clear lime-water, pass the sap into the first kettle and evaporate; then, when it is reduced to about one-half, dip it out into the second kettle, and skim it each time; then into the next, and so on, until it has reached the last, where it is reduced to syrup, and then may be thrown into a trough, and granulated by beating it up with an oar.
As soon as the first kettle is nearly empty, pour in a new lot of the sap, and so continue working it forward exactly after the manner of the West India sugar-boilers. The crude sugar may be refined subsequently, or at the time of casting it into the cones made of sheet iron, well painted with white lead and boiled linseed oil, and thoroughly dried, so that no paint can come off. These cones are to be stopped at first, until the sugar is cold; then remove the stopper and pour on the base of the cone a quantity of strong whiskey, or fourth proof rum. Allow this to nitrate through, until the sugar is white; dry the loaf, and redissolve it in boiling hot water, and evaporate it until it becomes dense enough to crystallise. Now pour it into the cones again, and let it harden. If any color remains, pour a saturated solution of refined white sugar on the base of the cone, and this syrup will remove all traces of color from the loaf.
One gallon of pasture maple sap yielded 3,451 grains of pure sugar. One gallon of the juice of the sugar cane yields, on an average, in Jamaica, 7,000 grains of sugar. Hence, it will appear that maple sap is very nearly half as sweet as cane juice; and since the maple requires no outlay for its cultivation, and the process may be carried on when there is little else to be done, the manufacture of maple sugar is destined to become an important department of rural economy. It is well known, by the Report of the Statistics of the United States, that Vermont ranks next to Louisiana as a sugar state, producing (if I recollect correctly) 6,000,000 of pounds in some seasons, though the business is now carried on in a very rude way, without any apparatus, and with no great chemical skill; so that only a very impure kind of sugar is made, which, on account of its peculiar flavor, has not found its way into common use, for sweetening tea and coffee. It would appear worth while, then, to improve this manufacture, and to make the maple sugar equal to any now in use. This can be readily accomplished, if the farmers in the back country will study the process of sugar-making, for cane and maple sugar are, when pure, absolutely identical. It should be remarked, that forest maples do not produce so much sugar as those grown in open fields or in groves, where they have more light, the under-brush being cleared away.
In Farmington, on the Sandy River, in Maine, I have seen a very fine grove of maples, but thirty years old, which produced a large yield of very good sugar. A man and two boys made 1,500 lbs. of sugar from the sap of these trees in a single season. The sap was boiled down in potash kettles, which were scoured bright with vinegar and sand. The sugar was of a fine yellow color, and well crystallised. It was drained of its molasses in casks, with a false bottom perforated with small holes—the cask having a hole bored at the bottom, with a tow plug placed loosely in it, to conduct off the molasses. This method is a good one, but the sap ought to be limed in boiling, as I have described; then it will not attach to the iron or copper boilers. The latter metal must not be used with acid syrup, for copper salts are poisonous.
There are several towns in the northern sections of Maine, New Hampshire, and Vermont, that produce more than sufficient sugar for the consumption of their inhabitants. A lot of good sugar trees will average four pounds to the tree, in a favorable season. Many farmers have orchards that will yield five hundred to a thousand pounds of sugar in a year. As this is made at a season interfering very little with the general business of the farm, the sugar that the farmer makes is so much clear gain.
There is, on almost every hill-farm, some place favorable for the growth of a maple orchard—some rocky spots yielding little grass, and impervious for the plough. Such spots may be favorably chosen for the growth of a maple orchard; and whether the increase be used for manufacturing sugar or molasses, or for timber or fuel, the proprietor of the land will find a profit better than money at interest in the growth of this beautiful tree, which will spontaneously propagate itself in many positions.
Its great excellence consists in yielding sap for the manufacture of vast quantities of maple sugar in the country during the months of spring. An open winter, constantly freezing and thawing, is a forerunner of a bountiful crop of sugar. The orchard of maple trees is almost equal to a field of sugar cane of the same area, in the production of sugar. This tree reaches an age of 200 years.
Vermont is the second sugar-producing State in the Union. The amount of maple sugar produced there in 1840 was over 2,550 tons, being more than 17¾ pounds to each inhabitant, allowing a population of 291,948. At five cents a pound, this is worth. 255,963 dols. 20 cents.