Revenue from Contracts with Customers - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Revenue from Contracts with Customers
Revenue	$ 64,871	$ 72,112	$ 197,255	$ 211,246
North America
Revenue from Contracts with Customers
Revenue	50,866	58,891	156,269	170,189
Asia
Revenue from Contracts with Customers
Revenue	8,517	8,052	23,329	25,148
Europe
Revenue from Contracts with Customers
Revenue	4,791	4,727	15,009	13,973
All other foreign
Revenue from Contracts with Customers
Revenue	697	442	2,648	1,936
Adhesives, Sealants and Additives
Revenue from Contracts with Customers
Revenue	22,922	26,009	73,184	78,814
Adhesives, Sealants and Additives | North America
Revenue from Contracts with Customers
Revenue	15,094	17,436	49,135	53,549
Adhesives, Sealants and Additives | Asia
Revenue from Contracts with Customers
Revenue	4,541	4,898	13,268	14,808
Adhesives, Sealants and Additives | Europe
Revenue from Contracts with Customers
Revenue	3,201	3,522	10,422	10,078
Adhesives, Sealants and Additives | All other foreign
Revenue from Contracts with Customers
Revenue	86	153	359	379
Industrial Tapes
Revenue from Contracts with Customers
Revenue	31,752	33,704	91,931	98,324
Industrial Tapes | North America
Revenue from Contracts with Customers
Revenue	28,137	31,691	81,811	89,672
Industrial Tapes | Asia
Revenue from Contracts with Customers
Revenue	2,239	1,303	5,642	5,217
Industrial Tapes | Europe
Revenue from Contracts with Customers
Revenue	840	561	2,386	2,101
Industrial Tapes | All other foreign
Revenue from Contracts with Customers
Revenue	536	149	2,092	1,334
Corrosion Protection and Waterproofing
Revenue from Contracts with Customers
Revenue	10,197	12,399	32,140	34,108
Corrosion Protection and Waterproofing | North America
Revenue from Contracts with Customers
Revenue	7,635	9,764	25,323	26,968
Corrosion Protection and Waterproofing | Asia
Revenue from Contracts with Customers
Revenue	1,737	1,851	4,419	5,123
Corrosion Protection and Waterproofing | Europe
Revenue from Contracts with Customers
Revenue	750	644	2,201	1,794
Corrosion Protection and Waterproofing | All other foreign
Revenue from Contracts with Customers
Revenue	$ 75	$ 140	$ 197	$ 223