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Note 3 - Inventory (Tables)
3 Months Ended
Mar. 31, 2022
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
  

March 31,

2022

  

December 31,

2021

 

Furnace parts and supplies

 $405,384  $213,224 

Raw materials

  2,186,304   2,144,067 

Work in process

  1,648,973   1,671,290 

Finished goods and filtration systems

  1,831,842   1,660,907 

Reserve for obsolescence

  (262,901

)

  (268,470

)

Net Inventory

 $5,809,602  $5,421,027