WOAD, in botany. See ISARIS.
The preparation of woad for dyeing, as practised in France, is minutely described by Altrue, in his Memoirs for a Natural History of Languedoc. The plant puts forth at first five or six upright leaves, about a foot long and six inches broad: when these hang downwards, and turn yellow, they are fit for gathering: five crops are gathered in one year. The leaves are carried directly to a mill, much resembling the oil or tan mills, and ground into a smooth paste. If this process was deferred for some time, they would putrefy, and send forth an insupportable stench. The paste is laid in heaps, pressed close and smooth, and the blackish crust, which forms on the outside, reunited if it happens to crack: if this was neglected, little worms would be produced in the cracks, and the woad would lose a part of its strength. After lying for fifteen days, the heaps are opened, the crust rubbed and mixed with the inside, and the matter formed into oval balls, which are pressed close and solid in wooden moulds. These are dried upon hurdles; in the sun, they turn black on the outside; in a close place, yellowish, especially if the weather be rainy. The dealers in this commodity prefer the first, though it is said the workmen find no considerable difference betwixt the two. The good balls are distinguished by their being weighty, of an agreeable smell, and when rubbed, of a violet colour within. For the use of the dyer, these balls require a farther preparation: they are beat with wooden mallets, on a brick or stone floor, into a gross powder; which is heaped up in the
the middle of the room to the height of four feet, a space being left for passing round the sides. The powder, moistened with water, ferments, grows hot, and throws out a thick fetid fume. It is shovelled backwards and forwards, and moistened every day for twelve days; after which it is stirred less frequently, without watering, and at length made into a heap for the dyer.
Woad not only affords a lasting and substantial blue, which, according to the scale of the dyers, may be reduced into many different shades, but is also of great use in dyeing and fixing many other colours. But notwithstanding this, and its being a commodity of our own, the use of it has very much declined since the introduction of indigo; for the purchase of which large sums go annually out of the nation. The reason of this is, that indigo affords a more lively and pleasing colour, is managed with more ease by the dyers, and does their business more expeditiously. Yet with all these advantages, it is universally acknowledged, that the colour which indigo affords is inferior to that of woad in many respects, and particularly in permanency; for which reason, they are frequently used in conjunction; woad to give solidity and substance, and indigo to give brightness and colour. But the worst consequence that has attended the use of indigo is, not barely lessening the consumption, but abating the price and depreciating the intrinsic value of woad; so that less care is taken in the management of it; to which in a great measure the inferiority of its colour, at least in some places, is at present owing. The declension in its consumption is not the case here only, but also in other countries; for it was once the great staple of Languedoc, and was cultivated also in Normandy, and in other provinces of France; as it also is in Spain, Portugal, the Azores, and Canary islands, Switzerland, in the neighbourhood of Geneva, in different parts of Germany, and in Sweden.
An idea has been entertained, that by an alteration in the manner of curing of it, the inconveniences that are supposed to attend the use of it might be removed, and that woad might be brought to answer all the purposes of indigo; which, if it could be accomplished, would be most certainly a great advantage, and an advantage which every true lover of his country would wish should take place here rather than any where else. The author of the Natural History of Languedoc suggests, that woad, if cured in the same manner as indigo, might produce as lively a colour; and adds, that from some experiments made by himself, he is convinced the method would effectually answer. The celebrated M. Du Hamel du Monceau informs us, that having proposed to Mr Fontenelle, a physician in Louisiana, the cultivating the pastel there in the manner of indigo, that gentleman acquainted him, that by treating indigo after the manner of pastel, he had obtained a very beautiful green: which indeed is always the case when the indigo is only allowed to absorb a small quantity of oxygen; for it is now well known that its blue colour is owing to the absorption of that gas.