Due to their large capital expense, pipelines are often utilized for the transfer of multiple products. During operation of these multi-product pipelines, the interface between two adjacent products extends (referred to as interface mixing), resulting in the contamination of each product. This interface is typically sent to slops collection for reprocessing or disposal at additional cost to the operator. Therefore the economics of a pipeline can often be improved through a study of product interfaces under various operational conditions to aide in the minimization of interface mixing. This article presents several empirical methods by which interface mixing can be quantified.