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

September 30,

2023

  

December 31,

2022

 

Furnace parts and supplies

 $60,826  $66,495 

Raw materials

  2,846,711   2,474,227 

Work in process

  1,305,301   982,973 

Finished goods and filtration systems

  1,242,106   1,201,533 

Reserve for excess and obsolescence

  (898,944

)

  (663,227

)

Net Inventory

 $4,556,000  $4,062,001