Isinglass, or fish glue, in its raw state, is the " sound," "maw," or swimming-bladder of various kinds of fish. The sounds undergo no other preparation than careful drying, but in the drying they are differently treated and made up, so that the isinglass comes into commerce under the names of "leaf," "staple," "book," "pipe," "lump " " honeycomb " and other designations, according to its form. The finest isinglass, which comes from Russia, is prepared by cutting open the sounds, steeping them in water till the outer membrane separates from the. inner, then washing the latter, and exposing it to dry in the air. Russian isinglass is obtained from several species of sturgeon (Acipenser), found in the Volga and other tributaries of the Caspian Sea, in the. Black -Sea, and in the Arctic Ocean. Brazilian isinglass, obtained from Brazil and Guiana, is the produce of a large fish, Silurus parkerii, and probably some other species. Manilla and East Indian isinglass is yielded by species of fish not yet satisfactorily determine The sounds of the common cod, the hake, and other Gadidce are also used as a kind of isinglass. (Encyc. Brit.)
The best quality of American isinglass is made from the sounds of the hake. The crude material is collected during the summer and autumn, coming from Maine, New Brunswick, Nova Scotia, and Prince Edward's Island. The conversion of the crude material into the mercantile article takes place in winter. A low temperature is necessary in order to turn out by machinery the fine ribbons of isinglass, and ice-water passes through the rolls. The total product is about 250,000 lb. Besides the use of isinglass for fining beer, etc, it is employed as a dressing or glaze for straw goods in the United States. (Scient. Amer.)
The manufacture of isinglass is carried on to a considerable extent in India, principally from the air-vessels of several varieties-of acanthopterygian fishes, and particularly different kinds of perch, as well as from other fish. (Nature.)
A very interesting product, called kanten, or vegetable isinglass - a species of gelose derived from either of the sea-weeds Gelidium corneum or Plocaria lichenoides - is made in China and Japan, and exported to Europe in flat and moulded tablets and in bundles of strips. It is known in Cochin China as hai thao, and is used in France in several industries especially in the preparation of goldbeaters' skin, and for rendering tissues impermeable. It is soluble in boiling water only, of which it takes up about 500 times its weight. It is manufactured as follows: - The seaweed, called by the native name of tengusa, is carefully washed and afterwards boiled, so as to form a gluish decoction, which is strained off and put into square boxes. When cool, it forms a stiff jelly, which can easily be divided into squares a foot in . length. The manner in which the surplus water is removed is very ingenious. The jelly prisms are exposed in the open air during a cold night, and allowed to freeze. During the day the sun melts (the water, which runs off, leaving behind what one might term the skeleton of white horny substance, which is extremely light and easily dissolved in water; when cooled, it again forms a stiff jelly.
This article can be applied to many purposes - for culinary uses, for making bonbons and jellies, for clarifying liquids as a substitute for animal isinglass, for making moulds used by the plaster of Paris workers, for hardening the same materials - in short, as a substitute for all kinds of gelatines, over which it has the advantage of producing a firmer jelly. Another seaweed much used for industrial purposes is the fu, resembling carrageen, or Irish moss, and applied to similar uses, such, for instance, as the sizing of the warp of silk goods. Recently the manufacture of an isinglass of this kind has sprung up in France, being made from the seaweeds found on the coast of that country. In its crude state it is a yellowish gelatine, but after repeated experiments under the auspices of the Industrial Society of Rouen, it has been successfully converted into what bids fair to prove the best sizing for cotton cloth known, and will probably entirely supersede the Asiatic product. Macerated in water for 12 hours, boiled for 15 minutes, and stirred till it becomes cold, the article gives a clear solution, which, as it does not again become a jelly, can be laid in its cold state upon any textile fabric and be left to dry.
One invaluable property it possesses is that of defying at common temperatures damp and mildew; and it is therefore being applied to give a lustre not only to French prints and muslins, but also to woollens and silks. In China, the first quality of the seaweed isinglass is used in a number of industries, especially in stiffening light and transparent gauzes, and the fine silk which is used for making fans, screens, hangings, etc. It is on these stuffs, so well stiffened, that the artists produce such beautiful designs in colours,incomparable for their freshness and brilliancy. A second quality of the article, of darker tint, is used by the makers of paper umbrellas, parasols, and lanterns, to smear the fine stretchers of bamboo on which they are formed. When thoroughly dried, these articles of such extensive use acquire an impermeability of long duration. (Scient. Amer.)
The seaweed Arachnoidiscus japoni-cusy which is used by the Japanese and Chinese to pack porcelain and other articles for exportation, is said to be made use of in France for the purpose of making artificial fruit jellies.
Consul Quin gives the following description of the method in which Japanese cut seaweed is prepared for the market: - For making the finest cut seaweed, the best long seaweed is used, the newer the better, on account of the colour. After the bundles are opened, they are picked, and as much sand as possible is shaken out; the selected weed is then placed in large boilers, and is boiled for an hour or more, until the proper colour is obtained, which should be quite uniform and of a good clear green. After boiling, the seaweed is hung up on poles in the air to partially dry it, after which it is again carefully sorted, and all ragged pieces and those of a pale whitish colour are rejected; the selected weed is then handed over to a number of women, who open it out and roll it into flat coils of about 10 lb. each. As soon as these coils have remained long enough to flatten the seaweed, they are uncoiled, and the pieces of weed are laid out one on the top of the other, on a board a little over 4 ft. long, to the depth of 8 to 10 in.; they are then cut into 4 lengths of 13 in. each, and these pieces are tied into bundles ready for the workmen to lay in the presses, which are about 6 ft. wide, 13 in. deep (the length of the pieces of seaweed), and 6 ft. high.