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Note 4 - Inventory (Tables)
9 Months Ended
Sep. 30, 2022
Notes Tables  
Schedule of Inventory, Current [Table Text Block]
  

September 30,

2022

  

December 31,

2021

 

Furnace parts and supplies

 $609,550  $213,224 

Raw materials

  2,157,268   2,144,067 

Work in process

  936,059   1,671,290 

Finished goods and filtration systems

  1,532,387   1,660,907 

Reserve for obsolescence

  (578,076

)

  (268,470

)

Net Inventory

 $4,657,188  $5,421,027