Preservation of paints in the wet-state

Because of the raw materials that they contain and the conditions under which they are manufactured and stored, water based paints are highly susceptible to microbiological infection and spoilage in the wet-state. The effects of microbial infection are viscosity loss, pH change, gassing, malodour and visible surface growth. In addition, discoloration and alteration in the rheology of the formulation can result in the product being unacceptable to the customer. However, the use of ever increasing concentrations of more highly active biocides is not the complete answer to these problems. Instead, the producer, with the help of the biocide manufacturer, must critically look at the whole production operation from a microbiological point of view. Improvements in plant hygiene, including examination and possible modification of plant design and more frequent and thorough cleaning, including the use of a biocidal wash, will help to alleviate problems. Changes in production practices, such as avoiding storage of stock thickener solutions and careful monitoring of raw materials will bring about further improvements. These activities, allied with the use of effective broad-spectrum biocides, will at least decrease incidences of microbiological contamination and at best eliminate such infections altogether. In this paper the author will attempt to answer the questions:- What are micro-organisms? What are they called? Where do they come from? Why do they grow in paint? What effects can they produce? How can they be prevented? Information will be given on a novel isothiazolinone combination biocide offering many advantages over traditional chloromethyl/methyl- and benz-isothiazolinone based preservatives.