Fluorimetric coat weight measurement

Abstract

A method and apparatus is disclosed for the on-machine measurement of coat weights of coatings applied to paper webs or the like. The invention provides an accuracy of plus or minus 0.1 pound per ream of coating in the coat weight range of from about 0 to 5 pounds per ream. Higher coat weights can be measured by practicing the method of the present invention, however the accuracy of the measurements of higher coat weights is reduced with an upper limit in the range of from about 10 to 20 pounds per ream depending upon the coating formulation being applied. The invention permits separate coat weight measurements of a web coated both sides and is carried out by including a small amount of a fluorescing optical brightener in the coating applied. The level of fluorescence of the optical brightener is continuously measured under a UV light source and the readings obtained are converted to determine the coat weight applied.

Dependencies are inferred from the claim text.