The invention relates to a preparation comprising a) 10 to 80% by weight of α,α′；,α″；-trimethyl-1,3,5-triazine-1,3,5-(2H,4H,6H) triethanol (TTT) and b) one or more additives selected from i) ammonia, ii) alkanolamines with primary amino group and alkyl group having at most eight carbon atoms and iii) alkylamines with primary amino group and alkyl group having at most eight carbon atoms, where the weight ratio a):b) is in the range from 100:30 to 100:1. The preparation is present as semi-concentrate and has an advantageously lower viscosity, is moreover storage-stable, in particular storage-stable over a long period.
