I > >I also understand that thymol crystals, which are extremely small, can >easily cause blindness. > >Ken Hoare Ken, A good word of warning. Substances with comfortable names like Thymol, Menthol and Camphor sound very non-threatening. However, if it was suggested that 2-isopropylphenol or (1a,2b,5a)-5-Methyl- 2-(1-methylethyl)-cycohexanol or bicyclic terpene ketone (the names for thymol, one form of menthol and camphor as I understand it) should be handled by beekeepers to treat varroa then caution would clearly be in order! These substances as well as the 'soft' acids are chemical products and all need to be treated with appropriate respect. regards, -- Mike Rowbottom HARROGATE North Yorkshire UK