Blue Glass Borax
and the student will get direct or collateral information by referr-ing to Asphalt Process, Chemigraphy, Collotype, Dag-uerreotype (etching of), Obernetter's Process, Fish Glue Process, Galvanography Leimtype, Woodbury Type, Zincography, Prism Reversing, Reversed Negatives and Types, originating by photographic means.
Blue Glass, for glazing the studio and for making lenses. Both these ideas were carried out at a very early period in photographic history, and are occasionally revived. A lens of blue glass is roughly achromatised by the cutting off of the yellow and green, but is much inferior to the usual cemented combination. Exposures in a studio glazed with blue glass are longer than in a studio glazed with colourless glass. A sheet of blue glass may be fixed over the ground glass of the camera as a means of damping the colour contrasts, and so enabling the photographer to judge better of the effect in the photograph.
Blue Printing Process. See Cyanotype.
Blue- Tones in Prints. Ordinarily a sign of over-toning, due to too great a deposit of gold (see Toning), or to sulphuration due to an acid toning bath.
Blurring. Any image possessing an indistinct or double outline is said to be blurred, and may be caused either by movement of the object or the camera. When photographing in a high wind, a loop of stout twine, tied to the bottom of the tripod, and hanging down to within 6 inches of the ground, in which the foot can be placed, will be found to steady it, or a bag may be attached to the string and filled with stones. (See also Halation.)
Books, Photographic See Bibliography.
Borax (Ger., borsdures natron; Ital., Borace). Na2B4Or, ioH20=i79. Synonyms: Pyroborate, Sodium borate, or Bibo-rate. It occurs in colourless octahedral crystals containing 30 per cent, of water, or in hexagonal prisms with 47 per cent, of water; also as an amorphous white powder. It is found native in various parts of the world, or made by neutralising boric acid with soda. Solubility: 6 per cent, in cold, 200 per cent.