Revenue from Contracts with Customers - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Revenue from Contracts with Customers
Revenue	$ 65,582	$ 66,631	$ 132,384	$ 139,134
North America
Revenue from Contracts with Customers
Revenue	51,928	52,974	105,403	111,298
Asia
Revenue from Contracts with Customers
Revenue	7,588	7,951	14,812	17,096
Europe
Revenue from Contracts with Customers
Revenue	4,947	4,952	10,218	9,246
All other foreign
Revenue from Contracts with Customers
Revenue	1,119	754	1,951	1,494
Adhesives, Sealants and Additives
Revenue from Contracts with Customers
Revenue	24,440	26,107	50,262	52,805
Adhesives, Sealants and Additives | North America
Revenue from Contracts with Customers
Revenue	16,335	17,566	34,041	36,113
Adhesives, Sealants and Additives | Asia
Revenue from Contracts with Customers
Revenue	4,284	4,678	8,727	9,910
Adhesives, Sealants and Additives | Europe
Revenue from Contracts with Customers
Revenue	3,642	3,778	7,221	6,556
Adhesives, Sealants and Additives | All other foreign
Revenue from Contracts with Customers
Revenue	179	85	273	226
Industrial Tapes
Revenue from Contracts with Customers
Revenue	30,055	31,158	60,179	64,620
Industrial Tapes | North America
Revenue from Contracts with Customers
Revenue	26,661	27,889	53,674	57,981
Industrial Tapes | Asia
Revenue from Contracts with Customers
Revenue	1,712	1,897	3,403	3,914
Industrial Tapes | Europe
Revenue from Contracts with Customers
Revenue	805	737	1,546	1,540
Industrial Tapes | All other foreign
Revenue from Contracts with Customers
Revenue	877	635	1,556	1,185
Corrosion Protection and Waterproofing
Revenue from Contracts with Customers
Revenue	11,087	9,366	21,943	21,709
Corrosion Protection and Waterproofing | North America
Revenue from Contracts with Customers
Revenue	8,932	7,519	17,688	17,204
Corrosion Protection and Waterproofing | Asia
Revenue from Contracts with Customers
Revenue	1,592	1,376	2,682	3,272
Corrosion Protection and Waterproofing | Europe
Revenue from Contracts with Customers
Revenue	500	437	1,451	1,150
Corrosion Protection and Waterproofing | All other foreign
Revenue from Contracts with Customers
Revenue	$ 63	$ 34	$ 122	$ 83