I guess it's good to know that isinglass is made from the air bladders of certain kinds of fish. But what in heck is isinglass? (Rhetorical question - I googled it - though I'm not sure I'm any clearer). Is it common in the US?
QQ, I followed you down the Insinglass rabbit hole and was amazed by how convoluted the story is. Not to mention how many explanations are offered as unquestioned fact, but offer only the vaguest evidence to support their claim. Since this sort of thing is food and drink to me, I offer what I learned for the benefit of anyone who might wonder about Isinglass but not be stupid enough to waste time researching it.
First off, let me say that I'd be surprised if many Americans have ever heard of Isinglass. If they have, chances are it's through the 1943 musical
Oklahoma! in which Curly sings in praise of "The Surrey with the Fringe on Top:"
"With Isinglass curtains you can roll right down
In case there's a change in the weather."This suggests that Isinglass is a flexible waterproof sheet that can be rolled up when the weather's nice and let down to protect against rain.
But the comic book "Righterong" feature says Isinglass is made from "the air bladders of certain fish." Did people actually make flexible side curtains for buggies out of fish bladders? Well, no. But the
statement in the "Righterong" factoid is Right while the
picture is Rong.
After surfacing from the depths of obscurity I'd learned that there are three distinct definitions of isinglass.
(1) a semitransparent whitish very pure gelatin prepared from the air bladders of fishes (such as sturgeons) and used especially as a clarifying agent and in jellies and glue. [Quoted from the Merriam-Webster dictionary website]. M-W doesn't mention another important product using isinglass as a clarifier: beer. Look up how Guinness is made, picture the bladder of a dead sturgeon, and see if your attitude toward stout has changed.
The fascinating thing about this kind of isinglass is that M-W traces its use back to the 16th century--to 1535, in fact. M-W speculates that the word (which had nothing to do with glass) originated
"probably by folk etymology from obsolete Dutch huizenblas, from Middle Dutch huusblase, from huus sturgeon + blase bladder" But then they go on to cloud the waters again in their "recent examples on the Web" section. A 2019 statement refers to a
"paper [that] was made of cloth, sometimes silk and isinglass, which is somewhat see-through and made from fish air bladders." This is followed by a 2017 reference to dark Norwegian cabins
"many of which did not have windows until the invention of isinglass in the 1600s." I was unable to find any other references to the translucent cloth. As for the second example, it sounds suspiciously like the article writer (a columnist in the
Milwaukee Sentinel writing about Norwegian wood carving) may have conflated fish-bladder isinglass with the
other definition of isinglass.
(2) "Mica especially when in thin transparent sheets." I've no idea why the mica "glass" came to be called isinglass, but it was a common term for
muscovite, a mineral which was first known as
"Muscovy-glass, a name given to the mineral in Elizabethan England due to its use in medieval Russia (Muscovy) as a cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century (Wikipedia article). This rock could be separated into large transparent sheets and was strongly heat-resistant. This sort of isinglass was often used for windows into furnaces or ovens. It's used widely today, including in electronics, paint, tires, wallpaper and even cosmetics.
Mica was thin, transparent, light, and weatherproof. However it was not flexible. It couldn't be "rolled up" like cloth. On an automobile history site and old-timer posted a family photo of a pre-1920 touring car featuring what his elders called "isinglass curtains." These were heavy (probably canvas) side panels which hung from the top of the open-sided car and latched to the running board. Six windows, about a foot high and two feet wide, had been sewn into the canvas. It's possible they were mica. The canvas side curtains could be rolled to some extent--more precisely folded--to store them. No one seemed to know, though, whether they really were mica or actually our
third isinglass definition:
(3) A generic everyday term once used to describe various forms of celluloid and other early plastics. Several online commenters mentioned their grandparents referring to transparent polyethylene items as "isinglass." Though polyethylene was invented in the 1890s, it didn't enter general use until the mid-1940s, its development spurred by World War II. Adults in that era would have learned the word isinglass in their youth and applied it to new plastic products.
"Adirondack Motorbooks and Collectibles" posted a definition which rolls up (har har) all the definitions into one:
"“ISINGLASS—typically a window made from thin sheets made of a material other than glass. Early isinglass was made from a transparent sheet of gelatin, processed from the inner lining of a sturgeon’s bladder. As it was flexible, it was perfect for the storm curtains and windows on early touring cars. The term is now commonly used as any non-glass sheet material which passes light, such as mica, oiled paper, celluloid or plastic. Early isinglass of all varieties yellowed and scratched easily.” (emphasis added).
I am still not convinced that storm curtain windows were processed from gelatin. For me the important point is that an array of different materials have been called isinglass. This point led me to a
fourth--and thankfully last--use of the word. It turns out that "isinglass" now can refer to the weather-resistant, transparent vinyl "window material" used on pleasure boats. Windows made from this stuff can indeed roll up, just like in the song, and are not only weatherproof and scratch resistant, they can be
"chemically resistant to suntan lotion, insect repellent and jet fuel vapor." The quote comes from an isinglass wholesaler's website, where they state categorically
"The confusion surrounding the word also comes from the fact that isinglass is semitransparent gelatin found in the air bladders of fish, particularly sturgeons, hake and cod. This isinglass is harvested and processed for a variety of uses. It was used throughout the 19th and 20th centuries in the manufacture of glue and cement. It’s still used today as a clarifying agent in jellies, wine and beer. The isinglass prepared from fish bladders has nothing to do with transparent window material; they just share a name.Class dismissed. There will be a test on Friday.