diff --git a/Graphs/gGraphView.cpp b/Graphs/gGraphView.cpp
index 1d4db2eb..62c284e1 100644
--- a/Graphs/gGraphView.cpp
+++ b/Graphs/gGraphView.cpp
@@ -147,6 +147,8 @@ GLBuffer::GLBuffer(int max,int type, bool stippled)
     m_cnt=0;
     m_colcnt=0;
     m_size=1;
+    m_blendfunc1=GL_SRC_ALPHA;
+    m_blendfunc2=GL_ONE_MINUS_SRC_ALPHA;
 }
 GLBuffer::~GLBuffer()
 {
@@ -308,7 +310,9 @@ void GLShortBuffer::draw()
         float size=m_size;
         if (antialias) {
             glEnable(GL_BLEND);
-            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+            glBlendFunc(m_blendfunc1,  m_blendfunc2);
+            //glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_TRUE);
             if (m_type==GL_LINES || m_type==GL_LINE_LOOP) {
                 glEnable(GL_LINE_SMOOTH);
                 glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
@@ -563,7 +567,7 @@ void GLFloatBuffer::draw()
     float size=m_size;
     if (antialias) {
         glEnable(GL_BLEND);
-        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+        glBlendFunc(m_blendfunc1,  m_blendfunc2);
         if (m_type==GL_LINES || m_type==GL_LINE_LOOP) {
             glEnable(GL_LINE_SMOOTH);
             glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
diff --git a/Graphs/gGraphView.h b/Graphs/gGraphView.h
index 719a2b73..fcd54971 100644
--- a/Graphs/gGraphView.h
+++ b/Graphs/gGraphView.h
@@ -73,6 +73,7 @@ public:
     void setAntiAlias(bool b) { m_antialias=b; }
     void forceAntiAlias(bool b) { m_forceantialias=b; }
     void setColor(QColor col) { m_color=col; }
+    void setBlendFunc(GLuint b1, GLuint b2) { m_blendfunc1=b1; m_blendfunc2=b2; }
 protected:
     int m_max;
     int m_type;     // type (GL_LINES, GL_QUADS, etc)
@@ -86,6 +87,7 @@ protected:
     bool m_forceantialias;
     QMutex mutex;
     bool m_stippled;
+    GLuint m_blendfunc1, m_blendfunc2;
 };
 
 /*! \class GLShortBuffer
diff --git a/Graphs/gLineChart.cpp b/Graphs/gLineChart.cpp
index cdad5beb..58c7077c 100644
--- a/Graphs/gLineChart.cpp
+++ b/Graphs/gLineChart.cpp
@@ -21,6 +21,7 @@ gLineChart::gLineChart(ChannelID code,QColor col,bool square_plot, bool disable_
     addGLBuf(lines=new GLShortBuffer(100000,GL_LINES));
     lines->setColor(col);
     lines->setAntiAlias(true);
+    lines->setBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC1_ALPHA);
 }
 gLineChart::~gLineChart()
 {
diff --git a/Graphs/gSummaryChart.cpp b/Graphs/gSummaryChart.cpp
index bc4cc5fb..1a376854 100644
--- a/Graphs/gSummaryChart.cpp
+++ b/Graphs/gSummaryChart.cpp
@@ -18,8 +18,10 @@ SummaryChart::SummaryChart(QString label,GraphType type)
     addGLBuf(quads=new GLShortBuffer(20000,GL_QUADS));
     addGLBuf(lines=new GLShortBuffer(20000,GL_LINES));
     quads->forceAntiAlias(true);
-    lines->setSize(2.5);
+    lines->setSize(1.5);
+    lines->setBlendFunc(GL_DST_ALPHA, GL_ONE_MINUS_DST_ALPHA);
     lines->forceAntiAlias(false);
+
     m_empty=true;
     hl_day=-1;
     m_machinetype=MT_CPAP;