Note 2 - Inventory - Summary of Inventory (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Furnace parts and supplies	$ 654,278	$ 596,806
Raw materials	1,605,809	1,659,826
Work in process	1,581,128	1,691,175
Finished goods and filtration systems	1,401,445	1,596,042
Reserve for obsolescence	(945,945)	(1,111,794)
Net Inventory	$ 4,296,715	$ 4,432,055

Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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