(_b_) Recording instruments often fail to give even approximately correct readings in rich latex. Errors may thus be made easily. (_c_) A fairly soft coagulum means easier working on the machines, less labour, and proportionately cheaper costs. [Illustration: THREE GRADES OF CREPE RUBBER. Left to right: fine pale crepe; second quality pale crepe; compound crepe.] It is advised, therefore, that for general purposes the same standard as that found suitable for sheet rubber should be taken--viz., 1-1/2 lbs. dry rubber per gallon. At all events the standard should not exceed 2 lbs. per gallon. COAGULATION AND COAGULANT.--Coagulation may be undertaken without any special arrangement of tanks, and is usually effected in the ordinary "Shanghai" glazed earthenware jars containing about 45 gallons. Given reasonable care, and a fairly fool-proof system of calculation for the quantities of chemicals required, no difficulty need be experienced. [Illustration: A WASHING SHED. Sheets are soaked in hot water in tanks in the background, and then scrubbed under a spray of cold water.] On a larger scale it is advised that proper reception tanks, in which standardisation can be effected, should be installed. Where both sheet rubber and fine crepe are being prepared, the whole system of sheet-coagulating tanks may be employed with considerable advantage, even to the insertion of the partitions. If ordinary jars are used, and the coagulum is left until the following morning, the mass of rubber has to be cut up into pieces of a size suitable for the machines. The knives or saws are sometimes rusty, and the colour of the coagulum is affected. The coolies often feed into the machines lumps which are too large, with the result that portions are thrust under the cheek-blocks and become stained. When a sheet-coagulating tank is used all labour of cutting the coagulum is obviated. The long strips are handled and fed into the rolls easily. It may be seen, likewise, that actual work is thus saved in machining. QUANTITY OF COAGULANT.--For a general discussion on the coagulant and quantities employed, the reader is referred to Chapter VIII. It is there recommended that for latex standardised to a level of 1-1/2 lbs. per gallon, the proportion of pure acetic acid should be in the ratio of 1:1,200. Directions are there given for the making of the solution, and the calculation of the quantity required for any given volume of latex. It is pointed out that for average _undiluted_ latex the basis of calculation, for quantities of acetic acid required, should be taken on the ratio 1:1,000. Where latex exceeds a dry rubber content of 3 lbs. per gallon, it may be necessary to increase the quantity of acid to 1:800.