a method of manufacture of soluble , microbiologically active and stable acrolein polymer comprising : polymerising acrolein in the presence of base to form a polymer of acrolein ; dissolving the polymer of acrolein in an alcohol selected from monoalcohols and polyols optionally with addition of water to form an alcohol solution of the polymer of acrolein ; heating the alcohol solution of the polymer of acrolein ; and mixing base with the polymer of acrolein .