The Bog Butter, as seen by first archaeologist on the scene, Rubicon's Ross MacLeod

Peat bogs are famous for preserving organic remains because of their high acidity, low temperatures and oxygen-poor conditions. As well as bog bodies, they occasionally preserve another remarkable archaeological material: bog butter.

Rubicon director Ross MacLeod was called to Shancloon near Caherlistrane in north Galway after peat-cutting works exposed a large timber object. Examination showed it to be a wooden cask containing about two stone, or 28 lb, of bog butter, potentially as old as 2,500 years. Bog butter may be dairy fat or animal tallow; at the time of discovery the exact composition of the Shancloon example had yet to be determined.

Two broad interpretations are commonly offered for these deposits. One sees them as votive offerings deliberately placed in bogs for ritual reasons. The other treats them as practical storage, with the cool bog acting as a form of refrigeration and the contents later lost or forgotten.

A seventeenth-century account even describes butter stored in wicker baskets and buried in a bog to develop a strong flavour for Lent. The discovery provided another example of the extraordinary preservation conditions offered by Irish peatlands.