ISINGGLASS, a preparation from the fish known by the name of hufa. See Accipenser. The word is Greek, formed of ἰχθύς, fish, and κόλλα, glue.—The method of making ifinglafs was long a secret in the hands of the Russians; but hath lately been discovered, and the following account of it published by Humphrey Jackson, Esq. in the 63d volume of the Philosophical Transactions.
"All authors who have hitherto delivered processes for making ichthyocolla, fish-glue, or ifinglafs, have greatly mistaken both its constituent matter and preparation.
"To prove this assertion, it may not be improper to recite what Pomet says upon the subject, as he appears to be the principal author whom the rest have copied. After describing the fish, and referring to a cut engraved from an original in his custody, he says: 'As to the manner of making the ifinglafs, the finewy parts of the fish are boiled in water till all of them be dissolved that will dissolve; then the gluey liquor is strained, and set to cool. Being cold, the fat is carefully taken off, and the liquor itself boiled to a just consistency, then cut to pieces and made into a twist, bent in form of a crescent, as commonly fold; then hung upon a string, and carefully dried.'
"From this account, it might be rationally concluded, that every species of fish which contained gelatinous principles would yield ifinglafs: and this parity of reasoning seems to have given rise to the hasty conclusions of those who strenuously vouch for the extraction of ifinglafs from sturgeon; but as that fish is easily procurable, the negligence of ascertaining the fact by experiment seems inexcusable.
"In my first attempt to discover the constituent parts and manufacture of ifinglafs, relying too much upon the authority of some chemical authors whose veracity I had experienced in many other instances, I found myself constantly disappointed. Glue, not ifinglafs, was the result of every process; and although, in the same view, a journey to Russia proved fruitless, yet a steady perseverance in the research proved not only successful as to this object, but in the pursuit to discover a resinous matter plentifully procurable in the British fisheries, which has been found by ample experience to answer similar purposes. It is now no longer a secret that our (A) lakes and rivers in North America are stocked with immense quantities of fish, said to be the same species with those in Mulcovy, and yielding the finest ifinglafs; the fisheries whereof, under due encouragement, would doubtless supply all Europe with this valuable article.
"No artificial heat is necessary to the production of ifinglafs, neither is the matter dissolved for this purpose; for,
(a) As the lakes of North America lie nearly in the same latitude with the Caspian sea, particularly Lake Superior, which is said to be of greater extent, it was conjectured they might abound with the same sorts of fish; and in consequence of public advertisements distributed in various parts of North America, offering premiums for the sounds of sturgeon and other fish, for the purpose of making ifinglafs, several specimens of fine ifinglafs, the produce of fish taken in these parts, have been lately sent to England, with proper attestations as to the unlimited quantity which may be procured. for, as the continuity of its fibres would be destroyed by solution, the mass would become brittle in drying, and snap short afiunder, which is always the case with glue, but never with ifinglafs. The latter, indeed, may be resolved into glue with boiling water; but its fibrous re-composition would be found impracticable afterwards, and a fibrous texture is one of the most distinguishing characteristics of genuine ifinglafs.
"A due consideration that an imperfect solution of ifinglafs, called fining by the brewers, possessed a peculiar property of clarifying malt liquors, induced me to attempt its analysis in cold subacid menstruums. One ounce and a half of good ifinglafs, steeped a few days in a gallon of stale beer, was converted into good fining, of a remarkable thick consistence: the same quantity of glue, under similar treatment, yielded only a mucilaginous liquor, resembling diluted gum-water, which, instead of clarifying beer, increased both its tenacity and turbidness, and communicated other properties in no respect corresponding with those of genuine fining. On commixing three spoonfuls of the solution of ifinglafs with a gallon of malt liquor, in a tall cylindrical glass, a vast number of curdly masses became presently formed, by the reciprocal attraction of the particles of ifinglafs and the feculencies of the beer, which increasing in magnitude and specific gravity, arranged themselves accordingly, and fell in a combined state to the bottom, through the well-known laws of gravitation; for, in this case, there is no elective attraction, as some have imagined, which bears the least affinity with what frequently occurs in chemical decompositions.
"If what is commercially termed long or short flapped ifinglafs be steeped a few hours in fair cold water, the untwisted membranes will expand, and reassume their original beautiful (b) hue, and, by a dexterous address, may be perfectly unfolded. By this simple operation, we find that ifinglafs is nothing more than certain membranous parts of fishes, divested of their native mucosity, rolled and twisted into the forms above mentioned, and dried in open air.
"The founds, or air-bladders, of fresh-water fish in general, are preferred for this purpose, as being the most transparent, flexible, delicate substances. These constitute the finest sorts of ifinglafs; those called book and ordinary flaple are made of the intestines, and probably of the peritoneum of the fish. The beluga yields the greatest quantity, as being the largest and most plentiful fish in the Muscovy rivers; but the founds of all fresh-water fish yield, more or less, fine ifinglafs, particularly the smaller sorts, found in prodigious quantities in the Caspian sea, and several hundred miles beyond Astracan, in the Wolga, Yaik, Don, and even as far as Siberia, where it is called ble or kla by the natives, which implies a glutinous matter; it is the basis of the Russian glue, which is preferred to all other kinds for its strength.
"The founds, which yield the finer ifinglafs, consist of parallel fibres, and are easily rent longitudinally; but the ordinary sorts are found composed of double membranes, whose fibres cross each other obliquely, resembling the coats of a bladder: hence the former are more readily pervaded and divided with subacid liquors; but the latter, through a peculiar kind of interwoven texture, are with great difficulty torn afiunder, and long resist the power of the same menstruum; yet when duly resolved, are found to act with equal energy in clarifying liquors.
"Ifinglafs receives its different shapes in the following manner:
"The parts of which it is composed, particularly the founds, are taken from the fish while sweet and fresh, slit open, washed from their slimy borders, divested of every thin membrane which envelopes the found, and then exposed to stiffen a little in the air. In this state, they are formed into rolls about the thickness of a finger, and in length according to the intended size of the staple: a thin membrane is generally selected for the centre of the roll, round which the rest are folded alternately, and about half an inch of each extremity of the roll is turned inwards. The due dimensions being thus obtained, the two ends of what is called short flaple are pinned together with a small wooden peg; the middle of the roll is then pressed a little downwards, which gives it the resemblance of a heart-shape; and thus it is laid on boards, or hung up in the air to dry. The founds, which compose the long-flaple, are longer than the former; but the operator lengthens this fort at pleasure, by interfolded the ends of one or more pieces of the found with each other. The extremities are fastened with a peg, like the former; but the middle part of the roll is bent more considerably downwards; and, in order to preserve the shape of the three obtuse angles thus formed, a piece of round stick, about a quarter of an inch diameter, is fastened in each angle with small wooden pegs, in the same manner as the ends. In this state, it is permitted to dry long enough to retain its form, when the pegs and sticks are taken out, and the drying completed; lastly, the pieces of ifinglafs are colligated in rows, by running pack-thread through the peg-holes, for convenience of package and exportation.
"The membranes of the book sort, being thick and refractory, will not admit a similar formation with the preceding; the pieces, therefore, after their sides are folded inwardly, are bent in the centre, in such manner that the opposite sides resemble the cover of a book, from whence its name; a peg being run across the middle, fastens the sides together, and thus it is dried like the former. This fort is interleaved, and the pegs run across the ends, the better to prevent its unfolding.
"That called cake-linglafs is formed of the bits and fragments of the staple forts, put into a flat metallic pan, with a very little water, and heated just enough to make the parts cohere like a pancake when it is dried; but frequently it is overheated, and such pieces, as before observed, are useless in the business of fining. Experience has taught the consumers to reject them.
(b) If the transparent ifinglafs be held in certain positions to the light, it frequently exhibits beautiful prismatic colours. "Ishinglaf is best made in the summer, as frost gives it a disagreeable colour, deprives it of weight, and impairs its gelatinous principles; its fashionable forms are unnecessary, and frequently injurious to its native qualities. It is common to find oily putrid matter, and exuviae of insects, between the implicated membranes, which, through the inattention of the cellerman, often contaminate wines and malt liquors in the act of clarification. These peculiar shapes might probably be introduced originally with a view to conceal and disguise the real substance of ishinglaf, and preserve the monopoly; but, as the mask is now taken off, it cannot be doubted to answer every purpose more effectually in its native state, without any subsequent manufacture whatever, especially to the principal consumers, who hence will be enabled to procure sufficient supply from the British colonies. Until this laudable end can be fully accomplished, and as a species of ishinglaf, more easily producible from the marine fisheries, may probably be more immediately encouraged, it may be manufactured as follows:
"The sounds of cod and ling bear great analogy with those of the acipenser genus of Linnaeus and Artedi; and are in general so well known as to require no particular description. The Newfoundland and Iceland fishermen split open the fish as soon as taken, and throw the back-bones with the sounds annexed in a heap; but previous to incipient putrefaction, the sounds are cut out, washed from their flimes, and salted for use. In cutting out the sounds, the intercostal parts are left behind, which are much the best; the Iceland fishermen are so sensible of this, that they beat the bone upon a block with a thick stick, till the pockets, as they term them, come out easily, and thus preserve the sound entire. If the sounds have been cured with salt, that must be dissolved by steeping them in water before they are prepared for ishinglaf; the fresh sound must then be laid upon a block of wood, whose surface is a little elliptical, to the end of which a small hair brush is nailed, and with a saw-knife the membranes on each side of the sound must be scraped off. The knife is rubbed upon the brush occasionally, to clear its teeth; the pockets are cut open with scissors, and perfectly cleansed of the mucous matter with a coarse cloth; the sounds are afterwards washed a few minutes in lime-water in order to absorb their oily principle, and lastly in clear water. They are then laid upon nets to dry in the air; but if intended to resemble the foreign ishinglaf, the sounds of cod will only admit of that called book, but those of ling both shapes. The thicker the sounds are, the better the ishinglaf, colour excepted; but this is immaterial to the brewer, who is its chief consumer.
"This ishinglaf resolves into fining, like the other sorts, in subacid liquors, as stale beer, cyder, old hock, &c., and in equal quantities produces similar effects upon turbid liquors, except that it falls speedier and closer to the bottom of the vessel, as may be demonstrated in tall cylindrical glasses; but foreign ishinglaf retains the consistancy of fining preferably in warm weather, owing to the greater tenacity of its native mucilage.
"Vegetable acids are, in every respect, best adapted to fining; the mineral acids are too corrosive, and even infalubrious, in common beverage.
"It is remarkable, that during the conversion of ishinglaf into fining, the acidity of the menstruum seems greatly diminished, at least to taste, not on account of any alkaline property in the ishinglaf, probably, but by its enveloping the acid particles. It is likewise reducible into jelly with alkaline liquors, which indeed are solvents of all animal matters; even cold lime-water dissolves it into a pulpy magma. Notwithstanding this is inadmissible as fining, on account of the menstruum, it produces admirable effects in other respects: for, on commixture with compositions of plaster, lime, &c., for ornamenting walls exposed to vicissitudes of weather, it adds firmness and permanency to the cement; and if common brick-mortar be worked up with this jelly, it soon becomes almost as hard as the brick itself; but for this purpose, it is more commodiously prepared, by dissolving it in cold water, acidulated with vitriolic acid; in which case, the acid quits the jelly, and forms with the lime a felineate mass, while, at the same time, the jelly being deprived in some measure of its moisture, through the formation of an indissoluble concrete amongst its parts, soon dries, and hardens into a firm body; whence its superior strength and durability are easily comprehended.
"It has long been a prevalent opinion, that sturgeon, on account of its cartilaginous nature, would yield great quantities of ishinglaf; but, on examination, no part of this fish, except the inner coat of the sound, promised the least success. This being full of rugae, adheres so firmly to the external membrane, which is useless, that the labour of separating them supercedes the advantage. The intestines, however, which in the larger fish extend several yards in length, being cleansed from their mucus, and dried, were found surprisingly strong and elastic, resembling cords made with the intestines of other animals, commonly called cat-gut, and, from some trials, promised superior advantages when applied to mechanic operations."
Ishinglaf is sometimes used in medicine; and may be given in a thin acrimonious state of the juices, after the same manner as the vegetable gums and mucilages, regard being had to their different disposition to putrefaction.