diff --git a/brew/water_optimizer.m b/brew/water_optimizer.m
index d6c4391..46bcbd3 100644
--- a/brew/water_optimizer.m
+++ b/brew/water_optimizer.m
@@ -53,13 +53,29 @@ A = 0*T
 Pa = [0 0 0 0]';
 Pp = [M_CaSO4; M_CaCl2; M_MgSO4; M_NaCl];
 
-Dn = 1;
-while Dn > 0.5,
-  [A1, Pa, Dn] = vecfit(Pp,mask,T,A,Pa, 0.0001.*(1-exp(-Dn)))
+CONV_COUNTER_RELOAD = 10;
+Dn0 = 1;
+conv_counter = CONV_COUNTER_RELOAD;
+while true,
+  [A1, Pa, Dn1] = vecfit(Pp,mask,T,A,Pa, 0.0001.*(1-exp(-Dn0)))
+  Dc = round_n(Dn1,3);
+  if Dn0 == Dc,
+    if conv_counter == 0,
+      break;
+    else
+      conv_counter -= 1
+    end
+  else
+    conv_counter = CONV_COUNTER_RELOAD
+  end
+  Dn0 = Dc;
 end
 T=T
 A1=A1
 Pa=Pa
 endfunction
 
+function zr = round_n(z, n)
+   zr = round(z*10^n)/10^n;
+endfunction