Note 12 - Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Inventories	$ 164,768	$ 145,844
Bad debts	4,659	8,773
Accrued liabilities	279,508	281,475
Prepaid expense	(116,524)	(95,371)
Depreciation and amortization	(2,798,040)	(2,928,232)
Research and development and other credit carryforwards	556,387	1,266,043
Right of use lease accounting	(19,600)
Directors stock option plan	163,427	62,134
Total deferred tax liability	(1,765,415)	(1,259,334)
Valuation allowance	(47,319)	(47,319)
Reserve for uncertain tax positions	(395,000)	(395,000)
Total reserves & allowances	(442,319)	(442,319)
Net deferred tax liability, net of reserves	$ (2,207,734)	$ (1,701,653)