least 0 8 percent or more preferably 1 0 or 1 2 percent in order to give the required dark green response it should be noted that tbpe actually gives a dark blue colour with vx but since vx also dissolves the yellow dye their resultant colour response is dark green in respect of all three dyes dye loadings up to about 2 0 might be utilized above that amount the detector becomes too expensive and in any event there is no significant improvement in detecting ability the paper base into which the dyes are incorporated can vary over a wide range of constituents a preferred formulation comprises in addition to a basic pulp formulation agents for improvement of wet and dry strength for ph control for water repellency and for binding purposes a typical formulation may contain a melamine formaldehyde resin to improve wet and dry strength and anionic emulsion of a sizing agent to impart water repellency sodium aluminate for ph control and provision of aluminum ions and alum for the provision of aluminum ions the aluminum ions interacting with pulp fibres to bind the sizing agent to the fibres a typical melamine formaldehyde resin is parez 607 tm a suitable sizing agent is newphor 100 tm the order of addition of the additives to the pulp slurry is important and comprises in order the resin the aluminum sodium aluminate the sizing agent and the dye slurries while the concentrations of the various additives may be varied over substantial ranges to suit particular conditions a typical and.