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Note 3 - Inventory (Tables)
6 Months Ended
Jun. 30, 2023
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
   

June 30,

2023

   

December 31,

2022

 

Furnace parts and supplies

  $ 62,468     $ 66,495  

Raw materials

    2,802,318       2,474,227  

Work in process

    1,153,817       982,973  

Finished goods and filtration systems

    1,137,315       1,201,533  

Reserve for obsolescence

    (732,638

)

    (663,227

)

Net Inventory

  $ 4,423,280     $ 4,062,001