many laboratory devices and test methods have been developed in order to enable the investigator to evaluate pulps retention aids fillers and other additives without resorting to a trial on a full size paper machine these include modifications of devices used to measure freeness and handsheet making equipment as well as devices designed specifically to measure retention standard handsheet making equipment such as a british hand sheet mold equipped with a means of re circulating white water can prove useful in laboratory studies the advantage in addition to being fast and simple is that the resulting handsheets can also be tested however these are static methods and do not simulate the turbulence and shear forces that the furnish would be subjected to on a paper machine the dynamic drainage jar developed by britt and unbehend attempts to simulate conditions encountered on a paper machine 16 the device determines the relative tendency of the fines fraction to pass through the screen with the fluid phase or to remain adsorbed as a part of the solid phase the result is expressed as retention of the fines fraction under selected and controlled turbulence conditions 16 li h m and scott w e 2000 tappi papermakers conference proceedings tappi press atlanta 2000 p 1 because it is not possible to duplicate the performance of a paper machine in an experimental device without in effect building an experimental paper machine with all the complexity of a real paper machine britt and unbehend argue that a laboratory device which measures the relative tendency of the.