There is provided a method of making an aqueous dispersion wherein said dispersion comprises (A) one or more thickener and (B) solid particles of 1,2-benzisothiazolin-3-one, wherein said method comprises the steps of (a) forming an aqueous mixture (I) comprising water, a dissolved salt of 1,2-benzisothiazolin-3-one, and optionally one or more thickener, wherein the pH of said aqueous mixture (I) is 8.5 or higher, and (b) subsequently forming said aqueous dispersion by mixing together, in any order, components, wherein said components comprise an acid, said aqueous mixture (I), and optionally one or more thickener, wherein the pH of said dispersion is 1.5 to 7.5. Also provided is an aqueous dispersion made by that method.
