INKS. 397 



line, and with this is to be mix<d lamp black, or black lead in fine 

 powdt r, so as to make an ink of a proper consistence, for printing 

 with types. Another, the blackish sulphate left after expelling 

 oxygen gas from oxide of manganese with a moderate heat being 

 dissolved and filtered, the dark grey pasty oxide left on the filter 

 is to be mixed with a very little solution of gum tragacanth, and 

 the cloth marked with this is to be dipped in a solution of potash or 

 soda, mild or caustic, in about ten parts of water. 



An ingenious correspondent, Mr. J. S. Gaskoin, has favoured us 

 with the following receipt for the composition of the u Chemical 

 Indelible Ink," sold for the purpose of marking linen. The linen, 

 that the black colour may be produced and fixed, is first moistened 

 with a mordant, which is a solution of soda, made thus ; take of 

 prepared soda 4 drams, distilled or common soft water 1 ounce, 

 saffron 1 grain, gum-arabic 15 grs. The constituents of the ink 

 are, lunar caustic 1 scruple, distilled water 1| dram ; or, if com. 

 ir.on soft water be used, two drops of nitrous acid should be added 

 to the solution. The mordant with which the linen has been mois. 

 tened being suffered perfectly to dry by a gentle heat, the part 

 where the limn has been moistened, is written upon with a clean 

 pen dipped in the ink. 



INK, fur the Rolling Press is made of linseed oil burnt in the 

 same manner as that for common printing ink, and then mixed 

 with Francfort black, and finely ground. There are no certain 

 proportions which can be determined in this kind of ink ; every 

 workman adding oil or black to his ink as he thinks proper, in 

 order to make it suit bis purpose. Some, however, mix a portion 

 of common boiled oil which has never been burnt ; but this must 

 necessarily be a bad practice, as such oil is apt to go through the 

 paper ; a fault very common in prints, especially if the paper is 

 not very thick. No soap is added ; because the ink is not cleared 

 off from the copper-plates with alkaline ley as in common printing, 

 but with a brush dipped in oil. 



[Pantologt'a. 



