Matchett proposed an exponential stress regime in silos from principal stress cap modelling. It could result in dangerously high stresses in silos. Practical examples of the exponential stress field have been found in the published work of Ramirez et al., for wheat and maize in a steel silo 1.9 m diameter and 5 m tall. The exponential stresses were found during the early stages of the discharge cycle. The data have been modelled by a modified, exponential, Janssen equation with the direction of wall friction reversed, and Matchett's principal stress cap model for a convex-active configuration. This phenomenon requires further investigation. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.