These low, stone-built structures were used to dry and then burn harvested seaweed, reducing it to a glassy, mineral-rich ash that was sold to manufacturers of glass and soap, and later as a source of iodine. The trade was at its most intense during the eighteenth and early nineteenth centuries, when landlords on the Atlantic seaboard encouraged or required tenants to harvest kelp as a cash crop, sometimes reserving the foreshore rights for themselves.

Connemara was among the most productive kelp-working regions in the country. Families would cut the weed at low tide, spread it across flat rocks or purpose-built drying areas to lose its moisture, and then burn it slowly in long stone troughs, stirring the molten ash with iron rods as it cooled and hardened. The resulting blocks were broken up and weighed before sale. The kiln at Loch Conaortha is a physical trace of that labour, set within a landscape where the boundaries between land and sea were always porous and the sea itself was a working resource rather than a backdrop.