Page:Paper and Its Uses.djvu/89

Rh or coated papers that the cause of the inclusion in the job list is not smell, for a customer cannot be expected to accept a big parcel of printed matter for circulation which is offensive to one of the finer senses, and therefore not likely to prove persuasive to the recipients.

Deterioration of paper has been dealt with already, but there are faults unwittingly developed in some paper which can be avoided by the application of a little forethought. The colouring matters of papers are affected by various things. Some blue colours are discharged (bleached) when acid in any form comes in contact with them, others behave similarly when alkali is encountered. Some buff papers are altered in shade or even in colour by the same agents, and other colours are affected by some but not by all acids. It is not proposed to examine the composition of the colours used by the papermaker, but to point to instances where care is required. When the printer or manufacturing stationer is covering strawboards, boxboards, or millboards with coloured papers, paste or glue may be employed as adhesive, and these are always liable to become acid. To avoid change of colour the use of freshly prepared paste or glue should be adopted. Strawboards frequently contain a certain amount of free alkali, and the colours of papers or cloth mounted upon them may be affected. It may be necessary to change the paper to one which is unaffected by the strawboard, and if this is not feasible, a change of board may be necessary. It is not practicable to neutralise the alkali, as fresh trouble may be caused, and an unsatisfactory result be obtained. Before starting on a big job, tests should be made with the actual materials so that no serious loss by spoilage or stoppage may occur.