C 374- ]

It is here somewhat more difficult to hit the due point ofboiling, than when the oil is prepared without addition;the mixture being more apt to grow too thick from con-tinuing the heat too long, and full of little hard grainsfrom not continuing it sufficiently; which grains are pro-bably undiflolved particles of the turpentine. The use©f boiling the turpentine first by itself is to dissipate itsmoisture or essential oil: by the boiling it becomes a re-sinous matter, nearly the same with common resin, whichpossibly would answer the same end.

For making the varnisti into ink, lamp-black is thecommon material; of which, according to Mr. le Breton,two ounces and a half are sufficient for sixteen ounces ofthe varnish. They are ground together on a stone witha muller, in the same manner as oil paints.

The paper, for printing, is moistened with water j bywhich it is made more yielding and pliable, so as not onlyto be less apt to be torn by the types in the press, butlikewise to be more closely and evenly applied to them,and consequently to take a neater and more perfect im-pression. The due moisture of the paper, and the careand attention of the pressmen in well working the inkon the types with the balls, are very material points;without which, how excellent soever the ink is, the im-pression will not be beautiful.

The adhesion of printers ink to wetted paper seems toshew that it is not truly of an oily nature. All expressedoils contain probably a gummy or mucilaginous matterand perhaps the tenacity, consistence, drying quality, andthe property of adhering to bodies moistened with water,which the oil acquires in the process above described,may be all owing to some of the purer part of the oilbeing destroyed, so as to leave the remainder more gum-my. When the oil dries, it proves a tough flexible sub-stance,