These kilns were used to burn harvested seaweed down to a grey, glassy ash called kelp, which was rich in alkali and iodine and sold to manufacturers of soap, glass, and later pharmaceuticals. The work was hard and seasonal, carried out by island families who cut and dried the weed through summer before firing it in long, shallow stone-lined trenches or pits.

The kelp industry along the Irish Atlantic coast reached its peak in the eighteenth and early nineteenth centuries, when the ash commanded reasonable prices from industrial buyers on the mainland and in Britain. On the Aran Islands, as elsewhere in Connacht, it supplemented the income of communities who worked small holdings on thin, difficult land. When cheaper sources of alkali became available through industrial chemistry in the mid-nineteenth century, the market for kelp collapsed, and the kilns fell quiet. What remains on Inis Oírr is a physical trace of that vanished economy, a modest structure that would be easy to walk past without knowing what it once produced or what it meant to the people who built and used it.