Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/327

297&#93; BLU with human urine, a fermentation is excited, and a due degree of moisture preserved by the addition of the same liquor. When it as- sumes a red colour, it should be removed into another vessel, again moistened with urine, and stirred, to renew the fermentation. In a few days the blue colour will begin to appear, and it must then be carefully mixed with a third part of pure powder of pot-ash ; after which it should be removed into Wooden pails, three, feet high and six inches broad. As soon as the third fermentation begins, it ought to be mixed with pulverized chalk or marble, The last gives no addi- tion but in weight. A fine, bine colour, equal to ul- tramarine, may be made by collect- ing the blue corn-bottle flower, or pentaurea cyamts, which abounds in almost every corn-field : it has two blue tin^s ; the one pale in the larger outward leaves, the other deeper, which lies in the middle of the flower ; by rubbing the last, while fresh, so as to express the juice, it will yield a beautiful and unlading colour. On the same day that the flower is gathered, the middle should be separated from the extremities, and when a quantity of die juice is ob- tained, a small addition of alum will produce a permanent, clear blue, which, in the opinion of many persons, is not inferior to ultramarine. Blue John, among miners, is a land of mineral which has lately been fabricated into vases and other ornamental articles. It is of the same quality as die cubical spar. At the foot of the high mountain called Mam-Tor, at Castleton, in perbyshire, it is still found in large BOA l>97 pieces, which are sold for about nine pounds per ton. BLUE-BOTTLE (Corn), or the Ccntaurea cyamm, L. is a plant common in corn-fields. See Wi- thering, 472 ; and Engl. Bot. 277. This vegetable is considered as a weed; but besides the property of affording a valuable paint, as mentioned in the preceding article, it is also much frequented by bee-;. A decoction of the flowers with galls and copperas, affords a good writing-ink; and it may also be employed with success in the dye- ing of linen or cotton. BLUEING, is the art of com- municating a blue colour to dif* ferent kinds of substances. Laun- dresses blue their linen with smalt; dyers, their stuffs and wools with wcad or indigo. Blueing 0/' metals is performed by heating them in the fire till they assume a blue colour ; it is parti- cularly practised by gilders, who blue their metals before the}' apply the gold and silver leaf. Blaring of iron, is a method of beautifying that metal for mourn- ing buckles, swords, &c. The pro- cess is as follows : Take a piece of grind-stone or whet-stone, and rub hard on the work, to take from it the black scurf; then heat it in the fire, and as it grows hot, the colour changes by degrees, appearing first of a light, then of a darker go'd colour, and lastly of a blue. Some- times they also giind indigo and salad-oil together 5 and rub the mixture on the work, while it is heating, with a woollen rag, leav- ing it to cool gradually. BOARD, a piece of timber sawed thin, for building, and odier pur j. oses. A cheap and durable composi- tion