Isinglass

At the start of Our Mutual Friend, Charles Dickens has Eugene Wrayburn refer to "our friend who long lived on rice-pudding and isinglass", the implication being that this was a poor diet. We are left in some doubt, however, for Dickens never mentions either rice puddings or isinglass again, and the only other people mentioning it are either quoting it or explaining what it meant.

In Oklahoma!, isinglass is the stuff of which curtains are made, so it must surely be bad for the digestion.

Isinglass, the OED tells us, gets its name from the great sturgeon Acipenser huso, which was called the huso or huse in Mediaeval Latin, and a hausen in German. Aside from being a source of caviar, this fish was the source of what the Dutch called the huisenblas, from the German hausenblase, which we call isinglass. 

The German hausenblase, we are told, literally means "sturgeon's bladder", and reminds us that isinglass was a whitish semi-transparent form of gelatin, obtained from the swim-bladders of sturgeons and freshwater fish, used first for making jellies and clarifying liquors.

Most isinglass was used to clarify wines and beers, in a process called "fineing", which took suspended particles out tannin and other foreign material out in a precipitate which was left behind when the liquor was cleared away, and the OED tells us that the word was used as far back as 1528, which raises an interesting question: why is William Murdock usually given the credit for inventing isinglass, when he was born in 1754 and died in 1839, long after the word was first recorded?

Murdock is actually better known for owning a wooden hat, which he turned on a lathe, and this ingenious piece of work supposedly won him a job with James Watt and Matthew Boulton; he invented the 'sun and planet gear' that is usually credited to Watt, and he invented coal gas, but if you dig down into the gaps, up comes the claim that Murdock invented isinglass.

In fact, what he invented was 'English isinglass', or "isinglass made of British fish", according to a judge who presided in a case brought against the users of William Murdock's isinglass in 1809.

To understand what was going on, Napoleon was causing all sorts of warlike activity across Europe, and so supplies of the best Russian isinglass were hard to come by, as battlefields kept springing up in the way of merchants.

William Murdock

So in 1795, William Murdock developed a substitute, based on cod skin and stale beer. Chemically, it was identical to isinglass, but the Solicitor-General decided some years later that it was adulterating English ale, and charged two brewers with the offence of adding both fish material and stale beer to their beer. Murdock pointed out that the isinglass actually settled out and so could not be an additive.

At the same time, the friendly judge, already familiar with the English isinglass was less than impressed, and when the famous Humphry Davy gave evidence, the case died. Oddly, another product, 'Irish moss', can also be used in the same way, as vegetarian beer drinkers like to point out. One is left suspecting that some kind of legal and political power play was involved, and certainly the Solicitor-General played one or two distinctly dirty tricks before he lost the case.

Along the way, though, isinglass had also come into its own as a clear or translucent sheeting, a sort of window material, but isinglass is an organic chemical, and poor at withstanding heat, and as early as 1688, mica was known as isinglass stone, and used in place of the protein sheets.

This raises the question, though, when Rodgers and Hammerstein have Curly, their hero sing in Oklahoma! of "isinglass curtains you can roll right down — in case there's a change in the weather", what sort of isinglass does he mean — the mica mineral type, or the gelatin fishguts type?

Given that the curtains could "roll right down", that probably means they were gelatin, though it may not have been gelatin from fish guts by then, but could equally have been derived from hides and hoofs of slaughtered cattle.

Nowadays, mica is no longer used in capacitors, and stoves with mica windows are rare indeed, so that leaves only the protein form of isinglass as a product still in use, at least among home wine makers, where it can be added to wine to clear it. But as William Murdock knew well, this is not really an additive, for the wine must then be drawn off into a fresh barrel or bottles.

Does this wine taste fishy to you?