To Benjamin Franklin from [Henry] Jackson, 29 July 1763
From [Henry] Jackson
Copy: Rutgers University Library
This extract of a letter and the accompanying remarks survive only in a copy headed “In a Letter from London to B. Franklin Esqr. which he sent me,” found among extensive manuscript notes on agriculture written, 1746–71, by Charles Read of Burlington, N.J.,3 and interleaved in a copy of John Worlidge, Systema Agriculturae (3d edit., London, 1681). The writer of the letter and remarks must have been Henry Jackson, a London chemist who, in addition to earlier writings on bread and tar water, published in 1765 An Essay on British Isinglass. What may have occasioned his correspondence with Franklin is not known, nor the reason why Franklin gave this paper to Read.
Eastsmithfield Londn. July 29 1763
A Method of Making Glue from Sturgeon &c.4
The Skin and Cartilages must be freed as much as possible from the other parts of the Fish and particularly from what are fat and unctuous, let them be washed clean and then boiled gently in a Sufficient Quantity of Water till they are disolved as much as possible or till little remains except some very gross Parts, The Liquor must be skimm’d pretty often, during the Coction and when it begins to grow thick, must be kept continually stirring to prevent burning; after wich the Decoction must be strained thro a fine wicker basket, permitted to settle an hour or 2 and then the clear Liquor must be evaporated in a proper Vessel till it is very thick, when it must be pourd into proper Moulds of Wood or Tin to stiffin, after wich it must be taken out and laid upon Netts stretchd in Frames, to dry till it becomes hard enough for Use.
Remarks
Copper Vessells for making Glues are most commodious. They must be of two kinds, One to boil the Subject in and the Other to evaporate the superfluous Moisture; The first may be constructed like a Brewers Copper fixed in Brick work with a Door, Grate, &c. After the Usual Method; The Other must be a double Vessel, or Water Bath, the outward Vessel of which, must be likewise set in Brick Work or the evaporating Vessel may be adapted to the Boiling Vessel wich thus may Answer two Purposes, first to boil the Subject in and afterwards receive the other Vessel to evaporate the Liquor, but where Dispatch in Busness is required it will be found to most advantage to have them seperate, that one may be boiling while the Other is evaporating; the double Vessel must therefore be very large in Diamiter and so shallow that altho it be large enough for its Companion to contain all the Decoction yet need not be more than 2 feet Deep or thereabouts; The two Vessels may be Set contiguous to each other with diffirent Flews in the same Chimney; The Companion to this shallow Pan must be adapted in such manner that it must be suspended within the Other by a broad Rim of Copper rivetted to its sides 6 Inches below [its] Edge or upper Rim, which Rim must rest upon the Edge or Top of the fixed Copper, the inward vesel must be less in Diamitir to the other, so as to leave 3 inches Space between the sides of the Two Vessels, every where around when the inner Vessel is suspended and 4 Inches Space from the bottom; At the Distance of every Foot in the Rim may be cut vent Holes, about Three Inches Long and two Inches Wide to let out the Steam of the boiling water in the outward Vessel; That Part of the inward Vessel above the Rim may be 6 or 8 inches that it may contain the more Matter to be evaporated, and be more readily taken out occasionally.
After the Glutinous Subjects have been disolved [word missing] slow continued boiling with repeated Quantities of water in the boiling Vessel; The Decoctions must be strained, permitted to subside in wooden Casks or tubs drawn off pretty Clear and put into the evaporating-vessel, previously suspended in the Other already filled 2 thirds with Water; The Fire must then be kept up, so as to keep the water round the inner vesel in a continued boiling State which water must be supply’d Occasionally as it wastes and the Decoction stir’d frequently till all the superfluous Moisture is evaporated and the Magma5 becomes just thin enough to pour into the moulds very slightly greased to prevent its sticking; In this state it must dry till it is stiff enough to lay upon Netts to be further dried for use; The Tin Pans need only to be made of a Sheet of tin, 6 or 8 inches Square, with the Edges turned up equal to the intended Thickness of the Glue Cake. The Nett Frames for drying resemble a little Hutt, They may be about eight Feet long as many high and Four wide, fixed about 6 inches distance from each other and one over another from the Ground to the Eaves of the Roof, wich Roof is weather boarded, the Hutt with its Roof must be built first, and the Frame with the Netts fastned within it afterwards; Thus the Netts will be open on all sides to the Air except the Top wich Defends them from Rain, the great Dificulty in making Glue is to prevent its burning which is effectualy done by this Method as the Decotion can receive no greater heat than [the] boiling water; The evaporating Pan is made broad and Shallow because all evaporations is in proportion to Surface exposed to the Air, Common Glue is generally of a brown Colour being generally a little burnt and full of heterogene particles, but Glue made after this Process will be the most perfect that can Possibly be made and will when finished appear tranparant and of a grenish Hue, it is the strongest that can be made and grows so hard between Timber as to resist moisture incredibly. Size is only Glue left in the Consist[ency] between Jelly and Glue, and Jellys are only thin Size, Papins Machine6 will disolve Animal Substance more readily, but is Inapplicable in a large way. Iron or Copper Ladles will be nessesasary to lade out the Glue; I know of nothing more worth describing but what will naturally occur to the Practitioner.
H Jackson
3. Charles Read (1715–1774), the third in a succession of five fathers and sons of the same name, was born in Philadelphia and established himself as a court clerk in Burlington, N.J., 1739, where he was soon also appointed customs collector of the port. He engaged extensively in land speculation, mercantile enterprise, and agricultural experimentation. He was the owner of the farm which writers and editors for many years ascribed to BF and which led many to credit BF with far greater activity in practical agriculture than the facts warrant (see above, III, 436). Read was deputy secretary of N.J., 1744–67; assemblyman, 1751–60; speaker, 1751–54; councilor, 1761–73; justice of the Supreme Court, 1749–53, 1762–73, and chief justice briefly in 1764. In 1773 he retired with impaired fortunes to the West Indies and died in No. Car. the next year. Carl R. Woodward, Ploughs and Politicks Charles Read of New Jersey And His Notes on Agriculture 1715–1774 (New Brunswick, 1941).
4. In contrast to the method described here, the manufacture of fish glue in the twentieth century relies heavily on the use of a variety of chemicals at various stages of the process. See George F. White, Fish Isinglass and Glue (Appendix IV to the Report of the U.S. Commissioner of Fisheries for 1917. Bureau of Fisheries Document No. 852. Washington, 1917).
5. A crude mixture of mineral or organic matters in the state of a thin paste.
6. In about 1680 the French physicist Denis Papin (1647–1714) invented a “steam digester, or engine for softening bones” under high pressure, which he described in a pamphlet La Manière d’amolir des os et de faire couire toutes sortes de viandes en fort peu de temps, et à peu de frais (Paris, 1682).