diff --git a/CMakeLists_files.cmake b/CMakeLists_files.cmake
index 313c51e58..740b85679 100644
--- a/CMakeLists_files.cmake
+++ b/CMakeLists_files.cmake
@@ -39,6 +39,7 @@ list (APPEND MAIN_SOURCE_FILES
       src/opm/common/utility/parameters/ParameterGroup.cpp
       src/opm/common/utility/parameters/ParameterTools.cpp
       src/opm/common/utility/numeric/calculateCellVol.cpp
+      src/opm/common/utility/numeric/RootFinders.cpp
       src/opm/common/utility/shmatch.cpp
       src/opm/common/utility/TimeService.cpp
       src/opm/material/fluidmatrixinteractions/EclEpsScalingPoints.cpp
diff --git a/opm/common/utility/numeric/RootFinders.hpp b/opm/common/utility/numeric/RootFinders.hpp
index de597307f..3f2f17839 100644
--- a/opm/common/utility/numeric/RootFinders.hpp
+++ b/opm/common/utility/numeric/RootFinders.hpp
@@ -22,66 +22,42 @@
 #define OPM_ROOTFINDERS_HEADER
 
 #include <opm/common/ErrorMacros.hpp>
-#include <opm/common/OpmLog/OpmLog.hpp>
 
-#include <string>
-#include <algorithm>
-#include <limits>
 #include <cmath>
-#include <iostream>
+#include <limits>
+#include <string>
 
 namespace Opm
 {
 
     struct ThrowOnError
     {
-        static double handleBracketingFailure(const double x0, const double x1, const double f0, const double f1)
-        {
-            std::ostringstream sstr;
-            sstr << "Error in parameters, zero not bracketed: [a, b] = ["
-                 << x0 << ", " << x1 << "]    f(a) = " << f0 << "   f(b) = " << f1;
-            OpmLog::debug(sstr.str());
-            OPM_THROW_NOLOG(std::runtime_error, sstr.str());
-            return -1e100; // Never reached.
-        }
-        static double handleTooManyIterations(const double x0, const double x1, const int maxiter)
-        {
-            OPM_THROW(std::runtime_error, "Maximum number of iterations exceeded: " << maxiter << "\n"
-                  << "Current interval is [" << std::min(x0, x1) << ", "
-                  << std::max(x0, x1) << "] abs(x0-x1) " << std::abs(x0-x1));
-            return -1e100; // Never reached.
-        }
+        static double handleBracketingFailure(const double x0, const double x1,
+                                              const double f0, const double f1);
+
+        static double handleTooManyIterations(const double x0,
+                                              const double x1, const int maxiter);
     };
 
 
     struct WarnAndContinueOnError
     {
-        static double handleBracketingFailure(const double x0, const double x1, const double f0, const double f1)
-        {
-            OPM_REPORT;
-            std::cerr << "Error in parameters, zero not bracketed: [a, b] = ["
-                      << x0 << ", " << x1 << "]    f(a) = " << f0 << "   f(b) = " << f1
-                      << "";
-            return std::fabs(f0) < std::fabs(f1) ? x0 : x1;
-        }
-        static double handleTooManyIterations(const double x0, const double x1, const int maxiter)
-        {
-            OPM_REPORT;
-            std::cerr << "Maximum number of iterations exceeded: " << maxiter
-                      << ", current interval is [" << std::min(x0, x1) << ", "
-                      << std::max(x0, x1) << "]  abs(x0-x1) " << std::abs(x0-x1);
-            return 0.5*(x0 + x1);
-        }
+        static double handleBracketingFailure(const double x0, const double x1,
+                                              const double f0, const double f1);
+        static double handleTooManyIterations(const double x0,
+                                              const double x1, const int maxiter);
     };
 
 
     struct ContinueOnError
     {
-        static double handleBracketingFailure(const double x0, const double x1, const double f0, const double f1)
+        static double handleBracketingFailure(const double x0, const double x1,
+                                              const double f0, const double f1)
         {
             return std::fabs(f0) < std::fabs(f1) ? x0 : x1;
         }
-        static double handleTooManyIterations(const double x0, const double x1, const int /*maxiter*/)
+        static double handleTooManyIterations(const double x0,
+                                              const double x1, const int /*maxiter*/)
         {
             return 0.5*(x0 + x1);
         }
@@ -427,7 +403,9 @@ namespace Opm
             cur_dx = -2.0*cur_dx;
         }
         if (i == max_iters) {
-            OPM_THROW(std::runtime_error, "Could not bracket zero in " << max_iters << "iterations.");
+            OPM_THROW(std::runtime_error,
+                      "Could not bracket zero in " +
+                      std::to_string(max_iters) + " iterations.");
         }
         if (cur_dx < 0.0) {
             a = x0 + cur_dx;
@@ -438,13 +416,6 @@ namespace Opm
         }
     }
 
-
-
-
-
 } // namespace Opm
 
-
-
-
 #endif // OPM_ROOTFINDERS_HEADER
diff --git a/src/opm/common/utility/numeric/RootFinders.cpp b/src/opm/common/utility/numeric/RootFinders.cpp
new file mode 100644
index 000000000..b644039c9
--- /dev/null
+++ b/src/opm/common/utility/numeric/RootFinders.cpp
@@ -0,0 +1,75 @@
+/*
+  Copyright 2010, 2019 SINTEF Digital
+  Copyright 2010, 2019 Equinor ASA
+
+  This file is part of the Open Porous Media project (OPM).
+
+  OPM is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  OPM is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <config.h>
+#include <opm/common/utility/numeric/RootFinders.hpp>
+
+#include <opm/common/ErrorMacros.hpp>
+#include <opm/common/OpmLog/OpmLog.hpp>
+
+#include <fmt/format.h>
+
+#include <stdexcept>
+
+namespace Opm
+{
+
+double ThrowOnError::handleBracketingFailure(const double x0, const double x1,
+                                             const double f0, const double f1)
+{
+    const auto str = fmt::format("Error in parameters, zero not bracketed: "
+                                 "[a, b] = [{}, {}]    f(a) = {}    f(b) = {}",
+                                 x0, x1, f0, f1);
+    OpmLog::debug(str);
+    OPM_THROW_NOLOG(std::runtime_error, str);
+    return -1e100; // Never reached.
+}
+
+double ThrowOnError::handleTooManyIterations(const double x0,
+                                            const double x1, const int maxiter)
+{
+    OPM_THROW(std::runtime_error,
+              fmt::format("Maximum number of iterations exceeded: {}\n"
+                          "Current interval is [{}, {}] abs(x0-91) {}",
+                          maxiter, std::min(x0, x1), std::max(x0, x1), std::abs(x0-x1)));
+    return -1e100; // Never reached.
+}
+
+double WarnAndContinueOnError::handleBracketingFailure(const double x0, const double x1,
+                                                       const double f0, const double f1)
+{
+    OPM_REPORT;
+    OpmLog::warning(fmt::format("Error in parameters, zero not bracketed: "
+                                "[a, b] = [{}, {}]    f(a) = {}   f(b) = {}",
+                                x0, x1, f0, f1));
+    return std::fabs(f0) < std::fabs(f1) ? x0 : x1;
+}
+
+double WarnAndContinueOnError::handleTooManyIterations(const double x0,
+                                                       const double x1, const int maxiter)
+{
+    OPM_REPORT;
+    OpmLog::warning(fmt::format("Maximum number of iterations exceeded: {}, "
+                                "current interval is [{}, {}]  abs(x0-x1) {}",
+                                maxiter, std::abs(x0-x1)));
+    return 0.5*(x0 + x1);
+}
+
+} // namespace Opm