Blue, Thumb′

Cake′-blue, Crown′-blue, Fig′-blue, Knob′-blue, Mech′lenburg-blue, (mēk′-), Queen’s-blue, Stone-blue, . Names given to the lump-blue used in laundries, which vary according to the quality and the particular form given to it. Prep. 1. A mixture of powdered starch with sufficient indigo (in impalpable powder) to give the nece ary colour, made into a stiff dough with starch-paste, and then formed into lumps or cakes of the desired size and shape, and dried. This forms the ordinary ‘washerwoman’s blue’ of the shops. 2. As the last, but substituting cæruleo-sulphate of pota a or blue carmine [226] for the ‘powdered indigo’ ordered in the last formula. Very fine. [226] See Indigo (Sulphate of). 3. As No. 1, but substituting whiting for the powdered starch and weak size, or a decoction of Irish mo for the starch-paste. Inferior. Uses, . Employed by laundre es to impart a faint blue tinge to linen, in order to increase its apparent whitene . The common forms given to it are that of small balls of about 3 ⁄ 4 to 1 inch in diameter; the same, but rather larger, and pinched with the thumb and finger in three directions, so as to leave corresponding depre ions ( THUMB-BLUE ); and cakes, which are cut out of the ma , previously rolled into a sheet, by a suitably shaped cutter.