Business Segments - Summary of company's operations (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	$ 10,028,000		$ 13,504,000		$ 19,088,000	$ 28,952,000
Costs of goods sold, inclusive of depreciation and amortization	(8,156,000)		(10,484,000)		(16,223,000)	(21,220,000)
Gross margin (loss)	1,872,000		3,020,000		2,865,000	7,732,000
Selling, general and administrative	(2,209,000)		(1,748,000)		(4,182,000)	(4,016,000)
Operating (loss)/income	337,000		(1,272,000)		1,317,000	(3,716,000)
Operating (loss)/income	1,848,000		(50,000)		3,517,000	(92,000)
Other income: employee retention credit (ERC)	1,914,000				3,644,000
Interest expense	(66,000)		(50,000)		(127,000)	(92,000)
Income (loss) before income tax provision	1,511,000		1,222,000		2,200,000	3,624,000
Income tax provision (benefit)	325,000		257,000		473,000	761,000
Net Income	1,186,000	$ 541,000	965,000	$ 1,898,000	1,727,000	2,863,000
Total Assets	52,563,000				52,563,000		$ 50,328,000
Capital expenditures					13,000	593,000
Operating Segments
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	10,028,000		13,504,000		19,088,000	28,952,000
Costs of goods sold, inclusive of depreciation and amortization	(8,156,000)		(10,484,000)		(16,223,000)	(21,220,000)
Gross margin (loss)	$ 1,872,000		$ 3,020,000		$ 2,865,000	$ 7,732,000
Gross margin %	18.70%		22.40%		15.00%	26.70%
Selling, general and administrative	$ (2,209,000)		$ (1,748,000)		$ (4,182,000)	$ (4,016,000)
Operating (loss)/income	(10,365,000)		(12,232,000)		20,405,000	25,236,000
Operating (loss)/income	(337,000)		1,272,000		1,317,000	(3,716,000)
Other income: employee retention credit (ERC)	1,914,000				3,644,000
Interest expense	(66,000)		(50,000)		(127,000)	(92,000)
Total other income / (expense)	1,848,000		(50,000)		3,517,000	(92,000)
Income (loss) before income tax provision	1,511,000		1,222,000		2,200,000	3,624,000
Income tax provision (benefit)	325,000		257,000		473,000	761,000
Net Income	1,186,000		965,000		1,727,000	2,863,000
Total Assets	52,563,000				52,563,000		50,328,000
Capital expenditures	(1,000)		180,000		13,000	593,000
Operating Segments | ATG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	7,823,000		11,230,000		15,046,000	25,044,000
Costs of goods sold, inclusive of depreciation and amortization	(6,242,000)		(8,494,000)		(12,452,000)	(17,860,000)
Gross margin (loss)	$ 1,581,000		$ 2,736,000		$ 2,594,000	$ 7,184,000
Gross margin %	20.20%		24.40%		17.20%	28.70%
Selling, general and administrative	$ (1,761,000)		$ (1,402,000)		$ (3,346,000)	$ (3,145,000)
Operating (loss)/income	(8,003,000)		(9,896,000)		15,798,000	21,005,000
Operating (loss)/income	(180,000)		1,334,000		752,000	(4,039,000)
Other income: employee retention credit (ERC)	1,573,000				2,986,000
Interest expense	(65,000)		(46,000)		(125,000)	(84,000)
Total other income / (expense)	1,508,000		(46,000)		2,861,000	(84,000)
Income (loss) before income tax provision	1,328,000		1,288,000		2,109,000	3,955,000
Income tax provision (benefit)	285,000		270,000		453,000	830,000
Net Income	1,043,000		1,018,000		1,656,000	3,125,000
Total Assets	43,300,000				43,300,000		40,826,000
Capital expenditures			128,000		10,000	541,000
Operating Segments | CPG
Segment Reporting Information [Line Items]
Revenues from unaffiliated customers	2,205,000		2,274,000		4,042,000	3,908,000
Costs of goods sold, inclusive of depreciation and amortization	(1,914,000)		(1,990,000)		(3,771,000)	(3,360,000)
Gross margin (loss)	$ 291,000		$ 284,000		$ 271,000	$ 548,000
Gross margin %	13.20%		12.40%		6.70%	14.00%
Selling, general and administrative	$ (448,000)		$ (346,000)		$ (836,000)	$ (871,000)
Operating (loss)/income	(2,362,000)		(2,336,000)		4,607,000	4,231,000
Operating (loss)/income	(157,000)		(62,000)		565,000	323,000
Other income: employee retention credit (ERC)	341,000				658,000
Interest expense	(1,000)		(4,000)		(2,000)	(8,000)
Total other income / (expense)	340,000		(4,000)		656,000	(8,000)
Income (loss) before income tax provision	183,000		(66,000)		91,000	(331,000)
Income tax provision (benefit)	40,000		(13,000)		20,000	(69,000)
Net Income	143,000		(53,000)		71,000	(262,000)
Total Assets	9,263,000				9,263,000		$ 9,502,000
Capital expenditures	$ (1,000)		$ 52,000		$ 3,000	$ 52,000