Paint clear-liquid separation

Clear-liquid separation is the appearance of a clear supernatant layer above the bulk of opaque paint after shelf-aging. This separation can occur within 1 day and be several inches thick in a 1-gal can. In tinted paints, colorant may float up into this layer and produce a very displeasing in-can appearance. Reincorporation of the supernatant layer by hand stirring or mechanical agitation usually solves the problem only temporarily because the clear-liquid layer returns after several days. HEUR/HEC- and HEUR/hydro-phobically modified HEC-thickened paints are particularly prone to this separation. 

If clear-liquid separation occurs, a third highly thixotropic, shear-thinning thickener can be incrementally blended in to determine the minimum amount required to stop the separation. Only small quantities of the third thickener should be used or the optimized paint rheology may change. 

Notes Third thickener blended into a 50/50 mid-MW HEUR/ mid-M W HEC-based paint that had a clear-liquid separation rating of 3. 

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