diff --git a/PyMca5/PyMcaGraph/backends/MatplotlibBackend.py b/PyMca5/PyMcaGraph/backends/MatplotlibBackend.py
index f4d4ae37c..1998403b7 100644
--- a/PyMca5/PyMcaGraph/backends/MatplotlibBackend.py
+++ b/PyMca5/PyMcaGraph/backends/MatplotlibBackend.py
@@ -67,55 +67,33 @@ def nanmin(x):
 TK = False
 if ("tk" in sys.argv) or ("Tkinter" in sys.modules) or ("tkinter" in sys.modules):
     TK = True
-if TK and ("PyQt4.QtCore" not in sys.modules) and ("PyQt5.QtCore" not in sys.modules) and\
-        ("PySide.QtCore" not in sys.modules):
-    if sys.version < '3.0':
-        import Tkinter as Tk
-    else:
-        import tkinter as Tk
-elif ('PySide.QtCore' in sys.modules) or ('PySide' in sys.argv):
-    matplotlib.rcParams['backend'] = 'Qt4Agg'
-    if 'backend.qt4' in matplotlib.rcParams:
-        matplotlib.rcParams['backend.qt4'] = 'PySide'
-    from PySide import QtCore, QtGui
-elif ("PyQt4.QtCore" in sys.modules) or ('PyQt4' in sys.argv):
-    from PyQt4 import QtCore, QtGui
-    matplotlib.rcParams['backend'] = 'Qt4Agg'
+if TK and ("PyQt5.QtCore" not in sys.modules) and ("PyQt6.QtCore" not in sys.modules) and \
+    ("PySide6.QtCore" not in sys.modules) and ("PySide2.QtCore" not in sys.modules):
+    import tkinter as Tk
 elif 'PySide2.QtCore' in sys.modules:
-    matplotlib.rcParams['backend'] = 'Qt5Agg'
     from PySide2 import QtCore, QtGui, QtWidgets
     QtGui.QApplication = QtWidgets.QApplication
 elif 'PyQt5.QtCore' in sys.modules:
-    matplotlib.rcParams['backend'] = 'Qt5Agg'
     from PyQt5 import QtCore, QtGui, QtWidgets
     QtGui.QApplication = QtWidgets.QApplication
 elif 'PySide6.QtCore' in sys.modules:
-    matplotlib.rcParams['backend'] = 'Qt5Agg'
     from PySide6 import QtCore, QtGui, QtWidgets
     QtGui.QApplication = QtWidgets.QApplication
 elif 'PyQt6.QtCore' in sys.modules:
-    matplotlib.rcParams['backend'] = 'Qt5Agg'
     from PyQt6 import QtCore, QtGui, QtWidgets
     QtGui.QApplication = QtWidgets.QApplication
 else:
     try:
         from PyQt5 import QtCore, QtGui, QtWidgets
         QtGui.QApplication = QtWidgets.QApplication
-        matplotlib.rcParams['backend'] = 'Qt5Agg'
     except ImportError:
         try:
             from PyQt6 import QtCore, QtGui, QtWidgets
             QtGui.QApplication = QtWidgets.QApplication
-            matplotlib.rcParams['backend'] = 'Qt5Agg'
         except ImportError:
             from PySide6 import QtCore, QtGui, QtWidgets
             QtGui.QApplication = QtWidgets.QApplication
-            matplotlib.rcParams['backend'] = 'Qt5Agg'
-if ("PyQt4.QtCore" in sys.modules) or ("PySide.QtCore" in sys.modules):
-    from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
-    TK = False
-    QT = True
-elif ("PyQt5.QtCore" in sys.modules) or ("PySide2.QtCore" in sys.modules):
+if ("PyQt5.QtCore" in sys.modules) or ("PySide2.QtCore" in sys.modules):
     from ._patch_matplotlib import patch_backend_qt
     patch_backend_qt()
     from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
@@ -131,6 +109,11 @@ def nanmin(x):
     TK = True
     QT = False
     from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg as FigureCanvas
+else:
+    QT = False
+    TK = False
+    print("Unknown backend. Defaulting to Agg")
+    from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
 try:
     from .. import PlotBackend
 except ImportError:
@@ -245,11 +228,7 @@ def twinx(self):
         # this respects aspect size
         # self.ax = self.fig.add_subplot(111, aspect='equal')
         # This should be independent of Qt
-        if matplotlib.rcParams['backend'] == "Qt4Agg":
-            FigureCanvas.setSizePolicy(self,
-                                   QtGui.QSizePolicy.Expanding,
-                                   QtGui.QSizePolicy.Expanding)
-        elif matplotlib.rcParams['backend'] == "Qt5Agg":
+        if QT:
             FigureCanvas.setSizePolicy(self,
                                    QtWidgets.QSizePolicy.Expanding,
                                    QtWidgets.QSizePolicy.Expanding)
diff --git a/PyMca5/PyMcaGui/PyMcaQt.py b/PyMca5/PyMcaGui/PyMcaQt.py
index 4778a8a9a..ec0e0078a 100644
--- a/PyMca5/PyMcaGui/PyMcaQt.py
+++ b/PyMca5/PyMcaGui/PyMcaQt.py
@@ -72,6 +72,8 @@
 elif hasattr(sys, 'argv') and ('--binding=PySide6' in sys.argv):
     # argv might not be defined for embedded python (e.g., in Qt designer)
     BINDING = 'PySide6'
+else:
+    BINDING = os.environ.get("QT_API", None)
 
 if BINDING is None: # Try the different bindings
     try:
@@ -87,23 +89,24 @@
             if "PySide6" in sys.modules:
                 del sys.modules["PySide6"]
             try:
-                import PySide2.QtCore
-                BINDING = "PySide2"
+                import PyQt6.QtCore
+                BINDING = "PyQt6"
             except ImportError:
-                if 'PySide2' in sys.modules:
-                    del sys.modules["PySide2"]
+                if 'PyQt6' in sys.modules:
+                    del sys.modules["PyQt6"]
                 try:
-                    import PyQt6.QtCore  # noqa
-                    BINDING = "PyQt6"
+                    import PySide2.QtCore  # noqa
+                    BINDING = "PySide2"
                 except ImportError:
-                    if 'PyQt6' in sys.modules:
-                        del sys.modules["PyQt6"]
+                    if 'PySide2' in sys.modules:
+                        del sys.modules["PySide2"]
                     raise ImportError(
-                    'No Qt wrapper found. Install PyQt5, PySide2, PySide6 or PyQt6.')
+                    'No Qt wrapper found. Install PyQt5, PySide6 or PyQt6.')
 
-_logger.info("BINDING set to %s" % BINDING)
+    _logger.info("BINDING set to %s" % BINDING)
 
-if BINDING == "PyQt5":
+if BINDING.lower() == "pyqt5":
+    BINDING = "PyQt5"
     from PyQt5.QtCore import *
     from PyQt5.QtGui import *
     from PyQt5.QtWidgets import *
@@ -124,8 +127,8 @@
     Signal = pyqtSignal
     Slot = pyqtSlot
 
-elif BINDING == "PySide2":
-    # try PySide2 (experimental)
+elif BINDING.lower() == "pyside2":
+    BINDING = "PySide2"
     from PySide2.QtCore import *
     from PySide2.QtGui import *
     from PySide2.QtWidgets import *
@@ -191,8 +194,9 @@ class QThread(_ExecMixIn, QThread): pass
                                                 _platform_plugin_path
             _logger.info("QT_QPA_PLATFORM_PLUGIN_PATH set to <%s>" % \
                              _platform_plugin_path)
-elif BINDING == 'PySide6':
+elif BINDING.lower() == 'pyside6':
     _logger.debug('Using PySide6 bindings')
+    BINDING = "PySide6"
     import PySide6
 
     from PySide6.QtCore import *  # noqa
@@ -232,8 +236,9 @@ def width(self):
             screen = QApplication.instance().primaryScreen() 
             return screen.availableGeometry().width()
 
-elif BINDING == 'PyQt6':
+elif BINDING.lower() == 'pyqt6':
     _logger.debug('Using PyQt6 bindings')
+    BINDING = "PyQt6"
     import enum
     from PyQt6 import QtCore
     if QtCore.PYQT_VERSION < int("0x60300", 16):
@@ -417,7 +422,9 @@ class _Foo(object): pass
     class QObject(QObject, _Foo): pass
 
 else:
-    raise ImportError('No Qt wrapper found. Install one of PyQt5, PySide2, PySide6, PyQt6')
+    raise ImportError('No Qt wrapper found. Install one of PyQt5, PySide6, PyQt6')
+
+_logger.info("PyMcaQt.BINDING set to %s" % BINDING)
 
 # provide a exception handler but not implement it by default
 def exceptionHandler(type_, value, trace):
@@ -470,7 +477,7 @@ def __init__(self, *var, **kw):
                 if (size.width() > 15) and (size.height() > 15):
                     self.setIconSize(size)
             except Exception:
-                print("unable")
+                print("unable to setIconSize")
                 pass
 
 if sys.version_info < (3,):
@@ -511,7 +518,7 @@ def safe_str(potentialQString):
 else:
     safe_str = str
 
-if BINDING=="PySide2":
+if BINDING.lower()=="pyside2":
     _logger = logging.warning("PyMca PySide2 support deprecated and not reliable")
 
 class CLocaleQDoubleValidator(QDoubleValidator):
diff --git a/PyMca5/PyMcaGui/misc/QIPythonWidget.py b/PyMca5/PyMcaGui/misc/QIPythonWidget.py
index 0fe5aa128..cb17f5956 100644
--- a/PyMca5/PyMcaGui/misc/QIPythonWidget.py
+++ b/PyMca5/PyMcaGui/misc/QIPythonWidget.py
@@ -32,7 +32,7 @@
 __contact__ = "sole@esrf.fr"
 __license__ = "MIT"
 __copyright__ = "European Synchrotron Radiation Facility, Grenoble, France"
-# Set the QT API
+
 import os
 import sys
 
@@ -40,16 +40,6 @@
                                     QPushButton, QVBoxLayout, QMessageBox, \
                                     BINDING
 
-# this seems to be obsolete stuff
-if BINDING == "PySide":
-    os.environ['QT_API'] = 'pyside'
-elif BINDING == "PySide2":
-    os.environ['QT_API'] = 'pyside2'
-elif BINDING == "PyQt4":
-    os.environ['QT_API'] = 'pyqt'
-else:
-    os.environ['QT_API'] = 'pyqt5'
-
 QTCONSOLE = True
 if sys.version_info < (3,):
     import IPython
diff --git a/PyMca5/PyMcaGui/physics/xrf/QtMcaAdvancedFitReport.py b/PyMca5/PyMcaGui/physics/xrf/QtMcaAdvancedFitReport.py
index 3898d1c3f..83ee82904 100644
--- a/PyMca5/PyMcaGui/physics/xrf/QtMcaAdvancedFitReport.py
+++ b/PyMca5/PyMcaGui/physics/xrf/QtMcaAdvancedFitReport.py
@@ -38,9 +38,7 @@
 QTVERSION = qt.qVersion()
 
 #this is installation dependent I guess
-from matplotlib import rcParams
 from matplotlib import __version__ as matplotlib_version
-#rcParams['numerix'] = "numeric"
 from matplotlib.font_manager import FontProperties
 from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
 from matplotlib.figure import Figure