The second half of the 1860s saw the biggest boom in the history of Gablonz glass bead jewellery. The capacity of local glassworks became inadequate and it was time for investment. Josef Riedel who was fully self-sufficient understood the need to invest. In 1865, he added a second and third furnace to his glassworks in Klein Iser. In 1866, he built a completely modern glassworks in stone, with two furnaces. In 1867 Josef established another works with two furnaces in Grünthal. The Grünthal works specialised in the production of chandelier trimmings and glass jewellery rods.