The present invention relates to a method, or process, for deriving compositional information from a multi-layer composition which includes the steps of obtaining multi-layer fractional composition information using a non-contact gauge such as an FTIR gauge; obtaining additional multi-layer composition information using a beta gauge; and, correcting for beta ray absorption differences among the layers of the multi-layer composition by combining the multi-layer fractional composition information with the additional multi-layer composition information obtained using the beta gauge.