diff --git a/dune/tectonic/frictionpotential.hh b/dune/tectonic/frictionpotential.hh
index 9498740fdee1ca919349ac3f77b44dae58ee981c..f0d6e64a536f70efaa021e1d8a03e4e4f4d4c50c 100644
--- a/dune/tectonic/frictionpotential.hh
+++ b/dune/tectonic/frictionpotential.hh
@@ -26,15 +26,11 @@ class FrictionPotentialWrapper {
   void virtual updateLogState(double) = 0;
 };
 
-// V log(V/V_m) - V + V_m  if V >= V_m
-// 0                       otherwise
 class FrictionPotential : public FrictionPotentialWrapper {
 public:
   FrictionPotential(double coefficient, FrictionData const &_fd)
       : fd(_fd), weightTimesNormalStress(coefficient * (-fd.normalStress)) {}
 
-  // log(V/V_m) if V >= V_0
-  // 0          otherwise
   double differential(double V) const {
     assert(V >= 0.0);
     if (V <= V_cutoff)
@@ -43,8 +39,6 @@ class FrictionPotential : public FrictionPotentialWrapper {
     return weightTimesNormalStress * fd.a * (std::log(V) - logV_m);
   }
 
-  // 1/V if V > V_0
-  // 0   if V < V_0
   double second_deriv(double V) const {
     assert(V >= 0);
     if (V <= V_cutoff)