BULLETIN OF THE UNITED STATES PISH COMMISSION. 295 



89.— SOIUK FACTS < !0 V 4 i: IC.M NG ININGLA88.' 



By niMtiK UMhsi:.\. 



It is probably well known that one of the most important qualities 

 of common glue is that it can gelatinate. As regards this property of 

 gelatinatiug, isiuglass prepared from fish-skins and heads differs very 

 materially from common glue, as it will but rarely, and only under cer- 

 tain conditions, form an incomplete jelly, which, during the succeeding 

 drying process, at a heat of 8° Celsius, will again become fluid or 

 dissolve, which prevents its being formed in tablets like the common 

 glue. It must therefore be considered as a characteristic quality of 

 isinglass that it does not easily turn to jelly, but that when strongly 

 concentrated, and at a low temperature, will stiffen so as to form a 

 tough mass. 



The usual process of preparing isinglass is as follows : When freshj 

 the air-bladder is taken from the back of the fish by striking the fish 

 several blows with a wooden club, whereby the sound is loosened, after 

 which it is torn from the btick and cut open lengthwise, so that it is 

 freed from any bones which may adhere to it. It is then placed in cold 

 water — sometimes in lime-water — where it remains some time. It is 

 then carefully cleaned of all blood, and the black outer skin is removed 

 with a knife ; whereupon it is again washed in fresh water, and spread 

 out on a board to dry in the open air, the inner shining skin being 

 turned outside. To prevent the sound from shriveling during the dry- 

 ing process, whereby it would lose its smoothness, it should at once be 

 fastened to the drying-board by small pegs or tacks. For obtaining a 

 good article of isinglass it is considered absolutely necessary that the 

 sound should be dried in the suu ; and for this reason swims cleaned 

 in winter are kept under the snow till spring. After the dryingprocess 

 is finished the sound is again moistened by drawing over it a brush 

 dipped in warm water, whoreupon the inner shining skin is removed 1 >y 

 hammering or rubbing. Finally it is rolled between two polished iron 

 rollers. 



Isinglass which is to be made into gelatine, before undergoing the 

 above-mentioned processes and while still in a moist condition, is bleached 

 in a solution of sulphuric acid, in which it swells up to a colorless jelly. 

 which, after having been dissolved in warm water and after the jelly 

 formed in cooling has become dry, will make a clear and colorless gela- 

 tine. 



To avoid the drying process, which cannot very well be done in winter 

 and during the busy fishing season, the sounds are salted and sold in 



* " Licit om Fiskelim." From Fiskeritidende, No. '23, Copenhagen, June 9, 1*35. 

 Translated from the Danish by Herman Jacobson. 



