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Preserving Butter Medieval Style

Brian KallerMy daughter burying butter in the bog

Like most people these days, we have a refrigerator to keep food fresh, and it runs on electricity — and here in Ireland, we get that from burning peat, or “turf.” A short walk from our house in the Bog of Allen, the land has been strip-mined to remove, press and dry the turf, in order to burn it in furnaces to boil water to run turbines to spin magnets to generate electricity to run refrigerators to keep food fresh.

Irish bogs are often misty and mysterious places, where local people would secretly speak their own forbidden language, teach children their faith, poach meat — and occasionally hide things. When farmers later drained areas of bog-land, they revealed the reddish ground under the water — thousands of years of compacted sphagnum peat moss, pressed into a solid mass. The farmers then scooped out the turf with special shovels, dried them at home, and burned them in the fireplace — and today, machines do the same thing on a vaster scale.

And sometimes turf-diggers unearth packages of butter — small as fists or big as barrels, wrapped in bark, wood or baskets. One recent discovery, a barrel of butter weighing more than 35 kilos, dated from 3,000 years ago — and many such discoveries have been eaten, and were reported to be delicious.

All the same, why butter, you ask? Probably because decomposers are slow to take apart fats anyway, and meat or vegetables would be more readily consumed. 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).

As with the other organic matter, butter did not go rancid in the waterlogged soil, and could be perfectly preserved after thousands of years. 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 — and remember, some of that fast-food meat might be more than a year in the freezer.

My daughter and I decided to do the same thing, making some butter at home and burying some in the bog-lands behind our house. In the old days this might have been done with a butter churn, but we were only doing small amounts, so we poured milk into a jar until it was half full and shook it — music is good for this part. At some point the sound of the sloshing changes, and you have a solid clump of butter in the middle of the liquid. In olden days many people would pat the butter dry of any milk-liquids, but we heated the solids off, not-quite clarifying it. Then we solidified it, wrapped it in cloth, and set off from our house.

Caroline Earwood, ‘Bog Butter: A Two Thousand Year History’, The Journal of Irish Archaeology, 8 (1997), 25-42.

James O’Laverty, ‘The True Reason Why the Irish Buried Their Butter in Bog Banks’, Journal of the Royal Society of Antiquities of Ireland, 2 (1892), 356-337.