Improved process for producing light-opaque pencil marks and pencils therefor

摘要

483,181. Pencils. BAUMANN, H., (formerly KOHNER, H.). March 18, 1937, No. 8021. Convention date, March 18, 1936. [Class 146 (iii)] In order to increase the light-opacity of the marks produced by pencil leads containing a dyestuff or a dyestuff component, the mark is subjected to a homogeneous layer of a solvent for the dyestuff or component preferably applied by means of a roller dampened with the solvent or as a gas of concentration at least equal to the vapour pressure of a saturated solution. When the lead contains only one component of the dye, the other component is applied in solution or gaseous form. The lead, which is free from water-repelling substances such as fat, and which preferably contains at least 20 per cent volume of hollow spaces, is impregnated with a solution of the dyestuff or component in a volatile solvent, so that at least one-third of the space is filled, and substances which do not repel water, such as glycerine, salts of higher fatty acids, or the like, are added. Dyes for cotton or cellulose are preferably used, e.g. water-soluble basic organic dyes such as nitrosophenol, nitro, azo, diphenylmethene, triphenylmethane, xanthene, naphthalene, or like dyestuffs. The paper or other support to be marked may also be treated to prevent spreading by lightly binding the dyestuff to the surface as by treating with tannin for basic dyestuffs, or inorganic salts such as common salt, calcium chloride, or the like for acid dyes.