Two miles north of Maquoketa on U.S. Highway 61 are lime kilns built in
the 1870's. The small town that supported the kilns, Hurstville, saw its near demise in the 1930s, the last time the kilns were fired.
Limestone rock mined from area quarries was fed into the four kilns and heated to form lime mortar used in building construction throughout the Midwest. This production of lime from native stone became one of Iowa's most important early industries.
The kilns produced quicklime from limestone. When limestone was heated to temps 750-1300 degrees F, carbon escaped leaving lime. This heating and cooling process took several days.
The Hurstville kilns were "draw" kilns that operated under the principal of gravity. Limestone was fed into the top of the kiln, it was ‘cooked’ by fireplaces on the sides of the kilns and the cooked stone removed. Draw kilns could be operated on a continual basis by removing the lime and the rock residue and feeding in more limestone. This process was extremely inefficient and the lumber needed to maintain the kiln fires resulted in the clearing of large tracts of woodland.
(Info and drawing from geo-caching.com)
No comments:
Post a Comment