130 



INK. 



Ink. 



be dipped in prussiate of poUssa, which makes any ten- 



~^n dency to change of colour to consist in the acquisition 



of a deep and rich blue tint. 



But, as this species of ink, after the best preparation, 

 is apt to decay, Dr. Lewis made attempts to form one 

 of still more durable materials. He found that a com- 

 position of black carbonaceous matter, such as lamp 

 black, with varnish, and half the weight of a thick mu- 

 cilage of gum arabic, formed an ink which, though it 

 was easily rubbed out with water on common paper, 

 proved in every respect durable when applied with a 

 pen to bibulous paper. The manuscripts of the an- 

 cients were written with lamp black and gum : and the 

 Chinese use a similar composition for all their writings, 

 the same which is sent to Europe under the name of 

 China ink, which they apply with a stiff hair pencil, 

 fixed in the end of a reed. When vinegar is used in- 

 stead of water in tempering ft, the ii\k sinks deeper 

 into the paper. Dr. Lewis ingeniously suggested as an 

 improvement, the union of the ancient with the modern 

 method, by adding a small portion of the ancient com- 

 position, or of Indian ink, to our common ink. In this 

 case, cotton must be used in the ink-stand, to prevent 

 the settling of the black powder. 



These methods are sufficient to secure every advan- 

 tage, where the effacing of manuscripts is not done by 

 design. But it has become, in recent times, an object, 

 on many occasions, to guard against frauds of oblitera- 

 tion. These are more easily executed since the disco- 

 very of the oxymuriatic acid, and its power in effacing 

 all inks made of the gallic acid, or vegetable astrin- 

 gents, with iron. For preventing the possibility of this, 

 when it is dreaded, an admixture of lamp black or other 

 burnt carbonaceous matter is effectual, and ought to be 

 in larger proportion than on other occasions. Finely 

 ground indigo is recommended by some along with the 

 lamp black. Others employ finely levigated manga- 

 nese, and others a solution of indigo in concentrated 

 sulphuric acid. The editor of the Annales des Arts, 

 vol. ii. p. 106, observes, that the common ink may be 

 rendered incapable of being discharged by any action 

 which the paper can withstand, if, instead of water, 

 the expressed juice of green vegetables be used, such 

 as the lathyrus, the sambucus niger, or common grass. 

 Indian ink. Indian or China ink, being an article possessed of 

 valuable properties, experiments were made by Dr. 

 Lewis to analyze and to imitate it. He found that the 

 adhesive ingredient in it was an animal glue, and he 

 formed very good imitations of it by means of glue and 

 lamp black. The superior delicacy of the imported 

 article seems to depend on the black. It brings differ- 

 ent prices, according to its fineness ; and this depends 

 on the kinds of oil from which it is produced. Various 

 oils are burned in that country, in chambers made for 

 the purpose. Du Halde gives three receipts for this 

 composition, on Chinese authority. In one of them, 

 the conglutinating ingredient is gum tragacanth ; this 

 must have formed an ink different from that brought 

 to us from China. In another it is thin size, and in a 

 third the size is mixed with a decoction of certain vegeta- 

 bles, which probably impart no quality excepting smell. 



Indelible ink, for marking linen, without being liable 

 to obliteration by washing, is merely a solution of ni- 

 trate of silver, with which the letters are traced after 

 the part to be written on has been dipped in a solution 

 of soda, and dried with a >trong heat. 



Inks of various colours may in general be made by 

 using a strong decoction of the ingredients used for dy. 

 ing, mixed with a little alum and gum arabic. 



Marking 

 ink. 



Coloured 



Red ink from an infusion of logwood. ink. 



Green ink from a solution of acetate of copper, with 1 *^~Y"^"' 

 gum arabic and white suga/. 



Blue ink from indigo, ground with white of eggs, and 

 brought to the due consistence by water. 



Yellow ink from an infusion of crocus, with alum and 

 gum arabic. 



Sympathetic ink is a substance with which writings Sympathe- 

 may be formed, which are invisible till they are sub- ti ink. 

 jected to some process, which immediately renders the 

 whole distinct. This purpose was fulfilled among the 

 ancients by means of milk, or some other viscous sub- 

 stance, which was rendered legible by means of soot 

 thrown over the writing ; part of it adhering wherever 

 the lines were drawn, while from every other part it 

 was blown entirely off. 



There are some articles employed for this purpose, 

 which are rendered visible by the addition of a sub- 

 stance which acts chemically. The materials of writing 

 ink may, for example, be employed in a separate state. 

 Invisible words may be first written with a solution of the 

 sulphate of iron. If a rag, dipped in a decoction of 

 galls, be drawn over them, they become immediately 

 legible. If this be afterwards rubbed over with sul 

 phuric acid, it is effaced. But the application of a sa- 

 turated solution of potassa will make it re-appear like 

 yellow writing. 



The golden sympathetic ink consists of a solution of 

 gold in nitro-muriatic acid, diluted with six times its 

 quantity of water. Letters traced with this are invi- 

 sible ; but when a similar solution of tin is applied to 

 them, the writing appears in the form of beautiful pur- 

 ple letters. Nitromuriatic acid is now capable of effa- 

 cing them, and the re-application of the muriate of tin 

 will restore them. Letters made with the muriate of 

 gold, indeed, become spontaneously visible when expo- 

 sed to the air. This, however, requires several days, 

 and, if kept closely shut up, they remain invisible for 

 two or three months. The acid evaporates, and leaves a 

 violet oxide or submuriate. Nitrate of silver affords 

 invisible letters, which become black by long exposure. 



There are many sympathetic inks which are ren- 

 dered visible by exposure to a fire. Solutions of mu- 

 riate of ammonia, and various other neutral salts, act 

 on paper by means of heat, in , such a way as adapts 

 them to this use ; but the letters become, in process of 

 time, confused and illegible. 



The best sympathetic inks are those made from ores 

 of arsenic, bismuth, or cobalt. Diluted nitric acid is 

 poured on arsenic ore, and afterwards carefully decant- 

 ed, treated with nearly half the quantity of dried 

 muriate of soda, and evaporated. Letters or figures 

 formed with this are invisible till held near a fire, which 

 renders them visible, and of a beautiful bluish green co- 

 lour. This disappears again when it is removed from 

 the fire. Alum, with the sulphate of soda, used instead 

 of muriate of soda, renders the substance red. Borate 

 of soda, or nitrate of potassa, also makes the letters ap- 

 pear red. 



The nitro-muriate of cobalt forms a similar ink, which 

 appears on exposure to heat, and disappears in theold. 

 The heat applied to it, however, must not exceed a 

 certain strength, otherwise the letters become perma- 

 nently visible both in heat and cold. These inks are 

 employed for making amusing landscapes, in which the 

 trees acquire a summer foliage as often as they are 

 brought near a fire. 



A sympathetic ink may be obtained from fresh urine, 

 evaporated, then dissolved in nitric acid, and saturated 

 1 



