diff -r 023ca640b5af -r 1365b5e47130 www/js/rec_edit.js
--- a/www/js/rec_edit.js	Mon May 13 12:50:24 2019 +0200
+++ b/www/js/rec_edit.js	Mon May 13 16:26:28 2019 +0200
@@ -169,9 +169,12 @@
 		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++) {
@@ -218,6 +221,7 @@
 				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);
 		}
 		to_100 = my_100;
 		if (to_100) {
@@ -235,8 +239,12 @@
 		preboil_sg = estimate_sg(sugarsm, parseFloat(dataRecord.boil_size));
 
 		// 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);