diff -r 023ca640b5af -r 1365b5e47130 www/js/prod_edit.js
--- a/www/js/prod_edit.js	Mon May 13 12:50:24 2019 +0200
+++ b/www/js/prod_edit.js	Mon May 13 16:26:28 2019 +0200
@@ -122,6 +122,7 @@
                         $("#ok_supplies").html("<img src='images/dialog-error.png'>");
 	}
 
+
 	/*
 	 * All calculations that depend on changes in the fermentables,
 	 * volumes and equipments.
@@ -140,9 +141,12 @@
 		var addedmass = 0;	// Added mass after boil
 		var mvol = 0;		// mash volume
 		var colort = 0;		// Colors srm * vol totals
+		var colorh = 0;		// Colors ebc * vol * kt
 		var my_100 = false;
 		var mashtime = 0;	// Total mash time
 		var mashtemp = 0;	// Average mash temperature
+		var bv = 0.925; 	// Bierverlies rendement
+                var sr = 0.95;  	// Mash en spoel rendement
 
 		if ((rows = $('#mashGrid').jqxGrid('getrows'))) {
 			for (var i = 0; i < rows.length; i++) {
@@ -189,6 +193,7 @@
 				vol += (x * sugardensity + (1 - x) * 1) * row.f_amount;
 			}
 			colort += row.f_amount * ebc_to_srm(row.f_color);
+			colorh += row.f_amount * row.f_color * get_kt(row.f_color);
 			// Check supplies.
 			if ((((dataRecord.inventory_reduced <= 2) && (row.f_added <= 1)) ||  // Mash or boil
                              ((dataRecord.inventory_reduced <= 3) && (row.f_added == 2)) ||  // Primary
@@ -255,8 +260,12 @@
 				dataRecord.brew_fermenter_sg = Math.round(plato_to_sg(pt) * 10000) / 10000;
 				$("#brew_fermenter_sg").val(dataRecord.brew_fermenter_sg);
 				// color
-				var cw = colort / (aboil_volume + top) * 8.34436;
-				dataRecord.brew_fermenter_color = kw_to_ebc(dataRecord.color_method, cw);
+				if (dataRecord.color_method == 3) {
+					dataRecord.brew_fermenter_color = Math.round((4.46 * bv * sr) /  (aboil_volume + top) * colorh);
+				} else {
+					var cw = colort / (aboil_volume + top) * 8.34436;
+					dataRecord.brew_fermenter_color = kw_to_ebc(dataRecord.color_method, cw);
+				}
 				$("#brew_fermenter_color").val(dataRecord.brew_fermenter_color);
 				var scolor = ebc_to_color(dataRecord.brew_fermenter_color);
 				$("#bcolorf").show();
@@ -271,8 +280,12 @@
 		}
 
 		// Color of the wort
-		var cw = colort / parseFloat(dataRecord.batch_size) * 8.34436;
-		var color = kw_to_ebc(dataRecord.color_method, cw);
+		if (dataRecord.color_method == 3) {	// Hans Halberstadt
+			var color = Math.round((4.46 * bv * sr) /  parseFloat(dataRecord.batch_size) * colorh);
+		} else {
+			var cw = colort / parseFloat(dataRecord.batch_size) * 8.34436;
+			var color = kw_to_ebc(dataRecord.color_method, cw);
+		}
 		dataRecord.est_color = color;
                 $('#est_color').val(color);
                 $('#est_color2').val(color);