34 is the ratio of of the resin retained on the fiber to the weight of the fiber expressed as percent in respect of mac the percent resin retained was determined by measurement in the case of the 2 solution and by extrapolation in the case of the 1 solution for urea formaldehyde the retention was assumed to be 50 of the resin available because extensive experience in the use of this resin has shown this rate to be generally true for sunrez the retention is an estimate based upon data pertaining to other formaldehyde free wet strength resins the actual value being unknown table 1______________________________________calipers and tensiles of treated handsheets resin caliper mm u00d7 10 sup 2 tensile g cm ______________________________________0 0 control 13 97 271 83 7 mac 1 soln 20 57 too weak to test7 4 mac 2 soln 22 86 too weak to test2 5 sunrez 17 o2 84 832 5 ufc 24 38 too weak to test______________________________________ it can be seen from table 1 that at the levels of addition employed and particularly using a 2 solution the maleamic acid copolymer is quite effective in modifying wood pulp fibers indeed its effect is comparable to that of the.