Bog butter

I have a new project I'll be announcing soon, but first: I mentioned a while ago that the BBC programme QI, former hosted by Stephen Fry and now by Sandi Toksvig, will be featuring my bog butter experiment on the show. With that in mind, I thought I'd rewrite and extend this piece a bit. 

When most people picture Ireland, they picture green fields and old stone walls, and that’s true of some places. Ireland also has lots of bog, though – the Bog of Allen, where we live, stretches almost a thousand square kilometres across several counties. Bogs are difficult to get through – they have few roads or villages even today – so they could be isolated, mysterious places, where characters in folktales met giants and fairies, a place where a starving and subjugated people could hide, or hide things.

A bog is a natural wetland, like a swamp or marsh – the difference is that the water is very acidic, so most kinds of plants can’t grow there – but peat moss does very well. Vast areas get covered in peat moss, and as layers of moss die off new layers grow over them, so you get gradually thickening layers of organic matter. In most circumstances it would just decay and become soil, like most things that die – but it’s soaking in dark, acidic water where fungi, insects, even most bacteria can’t survive, so it doesn’t decompose.

Over thousands of years it gets squeezed into a dark red solid called peat, or “turf” here in Ireland. For centuries this was the main fuel here, and kept many a potato farmer warm on a chill evening. That’s why this canal was built in the 1700s – turf was strip-mined from the bog, dried, loaded on carts, pulled by donkeys on these rails, and loaded here on barges to be brought to warm the houses of Dublin. The history and future of turf as a source of energy deserves its own video, but the point here is: Dead things buried in the bog don’t rot, so it’s an ideal place to store things.

People around here still fish out trees that fell in centuries ago and carve their wood into ornaments; the bog-water stained the wood almost black, but it’s still wood. Turf-cutters here find human bodies sacrificed by Druids thousands of years ago, their skins blackened and cured like leather but with their faces still recognisable. This might have been the inspiration for the dead marshes in Lord of the Rings, where you could still see the bodies of the dead under the water.

So people dig up many things from the past in the bog and meant to come back for -- necklaces, coins, tools, swords, 1,200-year-old prayer-books. And sometimes they find stores of food, up to 3,000 years old and not only intact, but edible. Specifically, they find butter.

Bizarre as that sounds, more than 430 caches of butter have been found in the bog, some small as fists, some big as barrels. The aforementioned 3,000-year-old butter weighed more than 35 kilos, the size of a child. And many of the apparently very adventurers discoverers any such discoveries have been eaten, and were reported to be delicious.

This doesn’t even count all the buried gastronomic treasure still waiting out there. Since we can suppose that people buried their butter to unearth and eat it later, and usually did so, these hundreds of finds must represent the small proportion of times that their owners died or the locations forgotten. This must have been a rather commonplace activity.

So why butter, you ask? A surprising number of foods around the world are preserved by being buried in the ground, but they are usually dried foods in arid climates (cheese in Italy), or sub-Arctic countries where the ground is freezing (salmon in Sweden), or where the food is meant to ferment in some way (eggs in China). In this case it’s waterlogged ground, it would probably disintegrate in the water over time unless it’s naturally waterproof, like fat.

This might have been done with meat as well; Archaeologist Daniel C. Fisher buried various meats in a frozen pond and a peat bog for comparison, and found that after a year, the meat buried in the bog had no more bacteria than the frozen meat. If this sounds gross, keep in mind that fast-food burger you last ate might have been more than a year old.  

Also, butter makes a valuable and high-calorie food for poor agrarian people; with it you can fry food or preserve things like potted meats. It was also taxed in medieval times, so burying it could have been a kind of tax evasion.

The constantly-cold Irish bog would keep the butter solid, and it would only age like cheese; in fact, the one taste-tested by Irish schoolchildren was said to taste like well-aged cheese. Some people might simply have liked the taste.

I like to experiment with old ways of preserving food; I learned how to preserve fruit over winter, how to preserve eggs in lime-water or isinglass, how to pickle vegetables or learn which mushrooms are edible. But in all those things I had people around to show me; lots of my older neighbours still make their own jam or wine. I don’t know of anyone who’s ever tried this who could show me how. Thankfully, it’s pretty straightforward – all you need is to access to one of the world’s peat bogs, and I happen to live in the middle of one.  

My daughter and I made some butter at home, which anyone can do; you just pour milk and cream into a jar, put on some music and start shaking. We couldn’t fill it more than a quarter full or we would just get whipped cream, so we had to do this many times to get the three pounds . At some point the sound of the sloshing changes, and you get a solid clump of butter in the middle of the liquid. Traditionally Irish housewives would pat the butter dry of its remaining liquids, but we simply clarified it. 

Then we froze it to keep it solid, wrapped it in cheesecloth and a rope, walked about ten minutes from our house into the bog. I paced the steps first in one direction and then another to make sure I would remember the spot, and tied the rope to a nearby tree to I could find it again.

Seventeen months later we dug up the butter, and while the picture looks pretty disgusting, once we washed it off and unwrapped it the butter looked much the same – a little darker yellow and with an earthy smell, but not rancid.  

The taste was similar – recognizably butter, with a slightly earthy, cheesy flavour a bit like parmesan; it was particularly good over popcorn. It wasn’t something most modern people would choose to eat regularly, but for people who faced periodic famines, it was an ideal store for lean times.

Of course, this butter was only in the bog for 17 months, and the effects are probably very different over 3,000 years. So I’m burying more butter for a longer period of time – dozens of kilos -- and planning to unearth it in about three to five years, some further down the road. If anyone wants to buy some in advance, you can be one of the few people in the world who can say they had this ancient food.