A Few Words About Formaldehyde

Our Human Remains Conservator Cat Irving discusses the misconceptions behind the use of formaldehyde and explains why you won’t see much of it in our Collections.

Peter Carey’s novel Jack Maggs is set in London in 1837. A Charles Dickens-esque character called Tobias Oates goes into a shop in Whitechapel where he buys what is purported to be the hand of a thief with long, delicate fingers. “This hand floated in a large wide-throated jar of formaldehyde…” At that point I threw the book across the room.

bOTTLE

There is a common assumption that anything preserved in fluid is in formaldehyde. It’s the most common thing that is said when I tell people that I’m a Human Remains Conservator: “Oh, things in formaldehyde!” This is rarely the case in collections I have worked with. Formaldehyde will do the job – it is the basis of most embalming processes, and Damian Hirst used it for his shark (albeit badly; the original shark began to decompose and had to be replaced). When talking about using formaldehyde in the early nineteenth century, the issue is largely one of dates: formaldehyde solution was first made accidentally in 1859, and the discovery of a production method followed in 1868. Commercial manufacture began in 1889. Following Joseph Lister’s paper on the importance of antisepsis, which would revolutionise surgery, there was a hunt for substances with antiseptic properties. It was thought that formaldehyde could be a contender – which is true, solutions stronger than 2% will kill micro-organisms; weaker solutions will merely arrest growth. A German scientist called Ferdinand Blum was studying this phenomenon in 1893, when he noticed that exposure to the solution hardened the skin on the tips of his fingers. Thus its fixative properties were discovered.

Much of Surgeons’ Hall’s collections pre-date Blum’s 1893 discovery. Instead, these are likely to be preserved in alcohol or in an oil – most commonly turpentine, but occasionally something else like cedar oil or wintergreen. Alcohol has a bleaching effect on tissue, while an oil will give a translucency that is useful if the tissue has been injected to show a particular structure. If something has been fixed using formaldehyde – the process of cross-linking the amino groups of cellular proteins to prevent the autolysis (breakdown) of the cells – I will usually store it in a glycerol-based solution. I often add a tiny bit of formaldehyde (around 0.5%) to this to prevent mould growth – those antiseptic properties I mentioned earlier. Minimising the use of formaldehyde is definitely a good thing: it has a strong smell and will irritate your nose and make your eyes water. It is also a known carcinogen; people who work around embalmed bodies on a regular basis show a higher than average incidence of leukaemia and brain cancers. I wear a formaldehyde respirator when working with it.

HEARTS
Two lambs’ hearts showing the effects of alcohol on tissue: The first is fresh, while the second has been stored in 80% ethanol for six months.

Two lambs’ hearts showing the effects of alcohol on tissue: The first is fresh, while the second has been stored in 80% ethanol for six months.

We can see from this that formaldehyde-as-preservative came along more than fifty years too late for Peter Carey’s poor hand, which was likely to be bobbing in some form of alcohol. The perception that formaldehyde is the only thing that can be used for storing tissue seems to have become fairly pervasive, but I hope I’ve managed to suggest that it is more complicated than that.

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