Washing Recycled Pulp Until It Stops Paying: Deinking Yield, Brightness and the Optimum Number of Wash Cycles for Small-Scale Production

This paper addresses a practical question in brightness: recovered newsprint is the cheapest fibre available to a small paper maker, but it arrives carrying printing ink, filler and short fibres that have already been used once. Using a self-contained computation from stated assumptions, the study evaluates the options across the range a small operation ordinarily meets and identifies the point at which the balance of cost, quality and material use changes. The headline findings are that optimum washes is 2; brightness at optimum is 58; yield kg at optimum is 95.6; net value usd at optimum is 38.43; net value usd no wash is 21; net value usd eight washes is 25.93. These figures come from a simulation study: the work is SIMULATED, NOT MEASURED, no physical trials were performed, and every number reported is taken from the deposited computation output so that any reader can reproduce or refute it with local values. The practical value of the result is a rule that can be applied at the point of work without further calculation, together with the tabulated cases from which the rule was derived and a statement of the assumptions on which it depends. Where the computation shows that a widely used practice wastes money or material, that finding is stated directly; where it shows that a popular economy is genuine, the size of the genuine saving is stated with equal directness, so that effort can be directed to the economies that are worth having.