Test specimens of slash pine (Pinus elliottii) and spotted gum (Eucalyptus maculata) were treated with aqueous emulsions of Busan 30WB and Busan 31, containing the fungicide TCMTB (2-(Thiocyanomethylthio)benzothiazole), or with solutions of TCMTB in toluene. These and matching untreated specimens were subjected to a wide range of procedures in an attempt to reveal TCMTB penetration patterns. Most candidate spot test reagents that produced colours with TCMTB in test tube solutions did not distinguish between treated and untreated wood, but the generation of nascent hydrogen in the presence of strong acid on the treated surface reliably produced a red colour, with intensity proportional to TCMTB content. The limit of detection occurs at 0.05 g TCMTB per 100 g wood. Mercaptobenzothiazole, related structurally to TCMTB, is the only other compound known to give a similar response.

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