Copper-plate Printing. — Speedy engraving of TVrit'ing, 63 



life of moveable charai^ers, becaufe they make them in wood, and ufe them to corrcift the Ac- 

 count of the State of China, which is printed at Pekin every three months. Duhalde does 

 not here feem to be aware of the ineftimable advantage of cafting types. The very celebrated 

 Dr. Franklin, who was long a printer at Philadelphia, Ihewed me fome effays which he had^ 

 made for fpeedily multiplying the copies of his own hand-writing. I do not here fpcak of 

 thofe Engiifh prefTes which anfwer the purpofe of a copyift, but of a procefs which gave birth 

 to that notion, a confiderable time afterwards. This method confifted in writing upon fmooth 

 paper, with ink containing much gum, which was afterwards fanded with emery, or powder 

 of caft-iron, and by means of a rolling-prefs, fuch as is ufed by the copper-plate-printers, the 

 ftrokes of the writing were transferred to a plate of rofe -copper, or pewter. This plate 

 afFords as many copies as the depth of the engraving can permit ; but it mufl: be confeffed, 

 thefe copies are very far from being beautiful, and the ground is fpotted and foiled. Taough 

 Franklin did not immediately communicate his procefs to mc, I fliewed him, before the 

 illuftrious Turgot, that by writing with a fteel point on a copper-plate, previoufly varnifii- 

 ed, a more fatisfadlory refult might be obtained by etching the ftrokes with nitric acid to a 

 fufficient depth for the fubfequent ufe of a liquid ink fimilar to that of the printers. In this 

 cafe the plate may be wiped without precaution, and tv;elve or more copies may be pulled ofF 

 upon coarfe paper. Thcfe proofs are foul and reverfed ; whence, in order to have them neat 

 and in the proper direction of the writing, it becomes neceflary to place the fame number of 

 leaves of white paper, wetted and prepared, upon the twelve proofs, and, while the ink is fiill 

 frefh, the whole being pafled together through the rolling-prefs, the fame number of counter- 

 proofs are obtained as there were proofs : fo that inftead of twelve turns of the prefs, thirteen 

 will be required to afford tv/elve'counter-proofs, very black, neat, and legible, even when the. 

 plate has not been perfeftly well wiped. This method is certainly not to be compared with 

 fine engraving ; but it may be ufeful in military operations, and all other cafes in which a fpeedy. • 

 multiplication of copies is required. No precaution is here necefTary: whether the nitrous 

 acid be more or lefs llrong, or remain a longer or fhorter time upon the plate, or whether the 

 plate be fomewhat heated to increafe the ftrength of the folvent, the fuccefs of the operation 

 will never fail ; provided the fteel point, made ufe of to trace the charadlers through the var- 

 nifh, fhall lay the copper perfedly bare. It is offadvantage that the nitric acid fhould bite deep, , 

 becaufe the counter-proofs are, by this means, much darker. The plate need not be well 

 wiped, becaufe it is of no confequence whether the proof which is ufed to afi'ord a counter- 

 proof fhould be very clean, provided it do not fpot the copy intended to be procured. The 

 moft liquid kind of printers' ink may be made ufe of. 



. The art of multiplying copies by a copper-plate engraved by excavation, appears to have 

 been an invention of the fifteenth century. The Italians and Germans contend for the honour 

 of this difcovery. This art, which is particularly diftinguifhed by the name of engraving, is, 

 neverthelefs, more generally attributed to a goldfmith of Florence, named Thomas Sini- 

 guerra. It is more efpecially ufed to tranfmit to pofterlty copies of paintings and defigns of 

 great mafters. Engravers, or rather copper-plate-printers, have, in certain circumftances,. 



made - 



