On the Manufacture of Indigo.

American Farmer, 5.12.1828.

(From the Southern Agriculturist.)

On the Culture, Gathering and Dyeing of the Indigo Plant, and the Manufacture of Indigo - by the Marquis de Fougere.

[Translated from the French.]

The gentlemen in South Carolina being perfectly well acquainted with the culture of indigo and the choice of seeds and soil, it is deemed unnecessary to translate that part of the author's instructions which relate to these objects.


Gathering of Leaves.

The proper time for cutting the plants, may be known by various signs which are more or less certain; it will always be known when the plants have arrived at perfect maturity and contain the greatest quantity and best quality of fecula which they can produce, when the greater part are in full blossom, and the seeds begin to appear.

The branches of the plant must be cut at about one inch from the stalk, with pruning knives or any other sharp instrument. When, after some time, the principal branches will have become stouter, it will be well to leave them and only to cut the secondary ones, in the way above mentioned.

This relates only to the indigo plant of Senegal; if the Bengal plant be cultivated, it will be necessary to cut (with sickles,) the whole plant at four or five inches from the earth, leaving on the stalk the inferior part of the first branches. The leaves must never be torn from the branches; for they would no longer be susceptible of being properly dried for the manufacture of indigo.

The cutting should never begin, but five or six days after a rain and in a day of warm weather, so that the leaves may, in one day, acquire such a de gree of dryness as will permit them to be kept in a heap without fermenting until the next day.

As the leaves which have been cut at sunset, can pass the night without alteration, they may be gathered from five o'clock until night, and the work may be resumed in the morning, and continued until half past eight o'clock only. It will be easily perceived, that in cases of emergency, the work may last all night. In all cases the plants must be transported in bundles to the dryers, and there immediately opened. They should be compressed to gether during as little time as possible; one hour being often sufficient to create heat, blacken them, and deteriorate the fecula which they contain.

The dryers generally consist of an area of flat brick-work, covered with cement and surrounded by a wall two feet high. In dry weather, when it has not rained for a long time, and the soil is perfectly dry, any spot will answer for this purpose; but care must be taken not to use a damp place, which would destroy the crop.

Dryers may be formed at once, vhich will unite all the requisites favourable to the prompt and com plete drying of the leaves, by plaring all their sur faces in contact with a current ot air, and by permitting them to receive the retlecton of heat from the soil, which by its nature, can tlrow out a great quantity. These dryers consist of a number of poles placed horizontally and eqially distant, and supported by forked stakes, driven into the soil, which should be covered with vey dry white sand. The dryers must be located on in open spot, distant from any pond, river or trees and to windward of any cause which might produe dampness.

Whatever way be the mode employed to dry the leaves, the branches must be e[x]posed to the rays of the sun at eight o'clock at arthest, one separated from the other, and never in a heap. At mid-day they should be turned overer, (when the air is very dry, the second kind of dryers, of which we have spoken, will avoid this trouble.) At half past four, all that has been dried during the day, must be united in heaps and beaten with rods, in order to detach the leaves from the branches; the latter should be set apart. The leaves must then be collected with brooms (a few of the branches lied (ogether will answer this purpose,) and trans ported to a dry place. It will be well to cover them with mats or sail cloth, without any compression. However, should they not be perfectly dry, it will be more advantageous to open them on the floor of a dry store-house, and lay them in strata of three or four inches, turning them over during the night, in order to prevent the generation of heat. This accident, which may lead to the total loss of the crop, must be studiously avoided.

[Here follow remarks which do not apply to South Carolina.]

The heat of the sun during one day will not always be sufficient to dry the leaves properly; the operation must be recommenced on the day following at nine o'clock, laying the leaves two inches thick, turning them over at times with rakes or wooden shovels; at three or four o'clock, (never later, in order to prevent the absorption of any moisture from the evening air,) fan them, in or der to separate the seeds and small sticks, heap them in a dry stack-house, whose floor should be boarded; then they should be strongly compressed and covered with mats; in fine, every precaution should be taken to preserve them from dampness, and, above all, from rain.

The leaves of indigo are known to be perfectly dry when they preserve a perfect unstained green colour, somewhat paler than that of the fresh leaf; when they can be easily reduced to powder by crumbling them between the fingers; (when kept for some time, they lose, without any injury, a part of this quality, but they should never be stored without it;) when they have the smell of dried clover, {lucerne,) and are free from brown or blue spots. la the latter state, they would yield little indigo, and it would be impossible to extract any from leaves in which either of these colours should be predominant.

When the indigo leaves have been carefully dried and possess all the requisite qualities, they may be preserved without alteration during two months, in a dry store, and may even be transported in bags. They should, however, be visited at times, and should they present any appearance of dampness or blackness, it will be prudent to expose them to the sun on a dry day, and to manufacture them as soon as possible.


Manufacture of Indigo.

The difficulties which attend the dessication of leaves, vanish in dry seasons. The care which we bestow by this method is amply compensated by the facility with which indigo is manufactured from the dry leaves: an operation which formerly required much experience and many days of labour, is now performed in less than twelve hours, by an intelli gent person who has witnessed it once. There are no particular phenomena to be observed, and the fermentation of twenty or thirty hours, during which one was exposed to lose his crop, or deteriorate the quality of it, is now reduced to a simple infusion of two hours. It is the watch that now guides the se ries of operations which lead to the extraction of indigo, during which time, the workmen are no longer exposed to unhealthy effluvia, especially when the workshops are kept clean.

I shall briefly describe the method of manufacturing indigo on a small scale, and in such a manner that the smallest planters may execute it them selves at little expense, and without other utensils than those commonly required in a family.


Workshop.

The workshop will consist of
1. A log house twenty feet long and twelve or fifteen feet broad, with a door in the centre.
2. Nine empty claret casks.
3. Two tubs, made from a wine cask, sawed in two.
4. Two churn staffs, made with a piece of board nine or ten inches square, and a handle fastened perpendicularly in the centre, and two spatulas, or paddles of wood.
5. Four wooden frames, fifteen inches square, coveted with coarse cotton cloth.
6. Six calabashes, of different sizes.
7. A large kettle, capable of containing twenty gallons.
8. A skimmer with a long iron handle.
9. Three or four boxes, a foot square, and six inches deep, with moveable tops and bottoms, perforated with small holes (l-10th of an inch in diameter,) on all their surfaces.
10. Three or four pieces of coarse cotton cloth, eighteen inches square.
11. A few blocks of wood, ten inches square and six inches thick.
12. A long and stout pole, for a lever to press the Indigo.
13. A few mats.

Remarks on No. 2. - The casks must be set up right, and one of the heads of each must be taken out. The diameter of four of these heads must be diminished by one inch. Eight of the casks must be perforated through one of the staves at the bot tom, with a hole of three quarters of an inch in diameter, and four of these will moreover be perforated with a hole half an inch in diameter, and Tour inches higher than the others. The casks should be of the best kind, properly cleaned and htted with strong iron hoops. The four casks which have but one hole, are designed for steeping the leaves, and may be called steepers. The other four, which are perforated with two holes, may be called receivers. The union of one steeper and one receiver, is called a set. The ninth cask will contain lime water, and is called the lime cask.

No. 3. The two tubs must be scraped in order to remove all the tartar and colour of wine lees, with which this wood is always impregnated; they more over should be strengthened with iron hoops. They are destined to receive the settlings of the receivers and to support the filters, No. 5.

No. 5. - These frames may be made with any sort of wood, provided they be strong. Covered with cloth, they are used as filters to drain the indigo.

No. 13. - The straw mats are used to dry the in digo, and to supply the place of a drying house. - They may be suspended on poles, supported stakes driven into the ground.


Location of the Workshop

The workshop should be located as near as possible to water; whether a river or well. The water may be either sweet or salt, but as a portion of the former is always necessary for boiling and washing the indigo, it will be better to use it entirely. Indeed, the operation of washing may be dispensed with, when sweet water has been employed in sleeping the leaves. The limpidness of the water conduces, in a great measure, to the beauty of the product.

The steepers should be so elevated, that in with drawing the stoppers, the water may run into the receivers.


Manufacture.

* The French wine casks contain about sixty gallons.

** The weight of a man on the leaves will be sufficient; a greater weight might injure the quality of the indigo.When a sufficient quantity of dried leaves have been collected, nothing can be more easy than the extraction of indigo. The operation is reduced to this: First, forty-four gallons of water in one of the steepers, (it will then be three-fourths full,*) add thirty-five pounds of dried leaves, (they must be fanned when they have been kept more than a fort night,) steep the leaves well, agitating them by means of the churn-staff, (No. 4;) renew this agitation twice during the two hours which the infusion or steeping must last; place, after two hours steeping, a filter, (No. 5,) on the receiver; draw out the plug from the steeper, (the small portion of leaves which may come out will be retained in the filter,) and the clear liquor will fall into the receiver; when the liquor, which must be green, will no longer flow, add, at different times to the leaves in the steeper, fifteen or twenty quarts of water; place, on the leaves in the steeper, the head of the cask, and let them be compressed** so as to give out the last portion of liquid which they may contain; compress with the hands the few leaves which may remain on the filter. The latter part of these operations will only require five minutes.

*** At in the act of churning butterWe must now proceed to the beating of the liquid, which is performed by moving the churnstuffs up and down.*** (During this operation, which lasts three-fourths or one half hour, according to the quantity, the scum passes successively through different shades of blue, until it arrives at that of Persian blue. When it has attained this colour, it passes gradually to that of a light blueish grey. As soon as this tint appears, the beating must be dis continued; generally there appears a slight excess of beating. It is known to be terminated, when on putting a small portion of the liquid into a glass, there appears small grains, which are detached and precipitated by the addition of a few drops of lime water, leaving the liquid in which they swim, clear and of a dark yellow colour.) In operating quickly on small quantities, the beating may be generally con sidered as terminated in three-fourths of an hour. At this time, ten or twelve quarts of lime water must be added, and slightly agitated, to mix the liquids; then allow the whole to settle.

The lime water is prepared by throwing four or five pounds of good lime into a cask of water, agi tiling for a few minutes and allowing it to settle. It should always be prepared before hand, and employed in a perfectly limpid state. It is drawn from the casks by means of the stopper.

In half an hour after the beating has terminated, the indigo is generally deposited at the bottom of the receiver. The upper hole must then be opened, in order to allow the mother tenter to escape; the indigo which is found at the bottom in a liquid state, must be placed on a filter to drain it. In the mean time the copper boiler must be filled twothirds with water, and (ire applied; the indigo in paste must be mixed in a calabash, with a small quantity of boiling water, and when it no longer presents any lumps, it must be thrown into the boiler, after straining through a piece of coarse canvass. The ebulition of the water is of course stopped by this addition, but it soon recommences, and must be checked twice by the addition of cold water. The flakes which may float must be care fully removed with the skimmer; the boiler must then he filled with cold water, and the fire withdrawn. The whole must be allowed to settle. The limpid water is drawn off from the indigo, and the latter drained on a filter. Should the first draining of water carry along any indigo, it must be again filtered.

When the indigo is sufficiently drained, that is to say, when no more water escapes from it, and it has arrived at the consistence of a thick paste and begins to split and separate from the filter, it is to be removed with a spatula into a calabash, and there agitated, in order to give it a uniform consistence. A wet cloth, (No. 10,) must then be applied to the boxes, (No. 9,) and so carefully spread as to produce no plaits or folds. The indigo must then be put in the boxes, and covered over with the edges of the cloth. The cover of the box must then be fitted, one of the blocks (No. 11,) applied over it, and the whole pressed gradually. When the water ceases to flow by this compression, the cover is removed, and the loaf of indigo is allowed to remain an hour in the box, in order to dry the cloth. With this precaution, the loaf is easily re moved. It must then be divided in equal squares, with a knife or wire, as is used in soap making. They must then be dried on the mats, (No. 13.) - This last operation must not be performed too hasti ly; the indigo must be screened from a draft of air, which would cause it to split. Ten days are gene rally required to dry the loaves, and they should be frequently turned over during this time. The indigo is sometimes covered with efflorescences, which should be removed by a brush or rags; this friction gives it a copper cast, and is called dressing.