The term Leca comes from Light Expanded Clay Aggregate. To produce Leca lightweight aggregates, clay is first transported from raw clay mines to the Leca factory processing unit. After sampling and precise chemical testing to ensure the absence of harmful chemicals and lime, the clay is mixed with water and formed into clay slurry, which is then fed into rotary kilns.
The clay slurry is heated to 1200°C, causing gases to expand the particles and form thousands of tiny cells inside them. As the material cools, the air bubbles within the particles remain as isolated voids, and their surface hardens.
Leca lightweight aggregates, or industrial Leca pumice, are roughly spherical with a rough and uneven surface. The microscopic exterior of the aggregates has fine brown pores, while the interior exhibits a black cellular structure. After production, the aggregates, in a 0–25 mm mixed size, are screened and separated into three size ranges: 0–4 mm, 4–10 mm, and 10–20 mm.