Tony Gronski
- Apr 30, 2020
- 4 min read

Sturgeon Isinglass: From Bookmaking to Breweries

From helping Roman performers walk on coals to aiding brewmasters in the fining process of malt liquors, sturgeon and its byproducts have been a versatile component of many trades. Derived from the German verb -Stoeren- meaning "wallow in the mud", sturgeon have assisted the advancement of civilizations dating back to Ancient Egypt in 1500 B.C. Since then, the sturgeon has been a fundamental part of technological advancements in Europe and Asia. Although less common today, the fish is still present and used in field-specific tasks.

Excerpts from early English literature depict the sturgeon as a harmless bottom feeder. The fish was known to swim up stream to spawn where British fishermen would cast nets in order to catch them. The process was not easy as the sturgeon was regarded by the British as a strong swimmer and would often break free from the nets. Records indicate sturgeon could reach up to 450 pounds in the area. Once caught, a sturgeon’s meat was well received across Europe with pickling being the most popular method of preparation. A sturgeon’s caviar paired with bread was also noted as a favorite of Greeks, Turks, and Venetians alike in the 17th century.

Depiction of Sturgeon System of Natural History

A strong argument can be made that a sturgeon’s value is not as a food source but as a key ingredient in countless products. In fact, the most valuable part of a sturgeon is not its meat. Rather, it is its swimming bladder. Also referred to as a sound, a sturgeon’s swimming bladder helps the fish control its buoyancy. The thin-lining membrane is known to be transformed into isinglass. A long process, the harvested bladder goes through a cleaning and drying process that produces a thin film. In most cases, after drying, isinglass could then be heated to sixty degrees Celsius where it would transform into a sticky substance. Over the years, people have found many creative uses for this material such as a base ingredient of glue, a heat resistor, an alcohol purifier, and a protective lining.

Isinglass Drying Technique from Humphrey Jackson

Starting in ancient Egypt, written records indicate the use of isinglass as an adhesive. Isinglass was also readily available to Roman physicians and pharmacologists. The isinglass glue functioned effectively as a wound-sealer. Physicians specifically applied isinglass to deep skull fractures and old wounds that would not close. Perhaps the most surprising use of isinglass during this time period would have to be its use as a heat-resistor. In the Hellenistic era, performers would apply the thin film to their feet where it would be used as a heat resistor. They would then be able to walk across coals neutralizing the heat being transferred.

Furthermore, artists and paper makers also benefit from using isinglass. Primarily used as a medium for painters, isinglass would be applied to improve the luster and/or translucency of the paintings. As for paper makers, isinglass was commonly used as a sizing agent in paper and fabrics. This provided the products with water resistance.

Hundreds of years later, the British found another use for isinglass. This time, it was used in the fining process of alcoholic beverages. In the 17th century, the thin film was placed in layers at the bottom of vats to be filled with malt beverages. The result: unwanted yeast particles and other contaminants would attach themselves to the inserted isinglass. When the time came, the polluted isinglass would be removed. This process has continued into the 21st century with many beers still being produced using this process to this day. In fact, up until 2016, Guinness listed isinglass as an ingredient in its stout.

In more recent times, the sturgeon commodity has made its way into the hands of librarians and professors. First used as a conservation tool in the 17th century, today, isinglass still has practical uses particularly with paper and art restoration. The substance has long been considered one of the purest adhesives. Russian sturgeon glue is considered a favorite among conservators familiar with the process. Isinglass is a suitable lining for pastel artwork, an excellent painting medium, and used as a glue for damaged parchment. The byproduct of sturgeon makes for the perfect glue and fits all conservation criteria. Its neutral pH level helps minimize harmful long-term effects, and the fish glue is easily reversible with heat and moisture. Arguably most importantly, its non-toxic chemical properties do not pose a threat to the original piece of work. In most cases, a starch-based glue is favored over its sturgeon substitute due to price and market availability. For fragile applications, however, isinglass is the most popular choice due to its flexibility and low surface tension compared to alternative glues. In scenarios where little water is necessary, isinglass can be mixed with glycerin or honey to provide similar adhesion. In unfavorable conditions, isinglass is the best choice given its holding strength and transparency.

Dried Isinglass

Over the course of 3500 years, the sturgeon has played an intricate role in nations around the world. Through those years, the use of isinglass is well documented in a wide array of fields. The sturgeon can be found throughout history in the bags of Roman physicians, the breweries of England, the hands of painters, and now at the disposal of book conservators around the world. Since its fist production, few alternatives have been found that match the results isinglass provides. Isinglass has maintained its timeless value through the advancement of technologies.