The effect of adding urea to the dyebath on the rate of absorption of reactive and acid dyes by wool, and of acid dyes by other protein bres, has been studied. Possible modesof action of aqueous solutions of urea on wool are discussed. The observed increase in the ite of dyeing in the presence of urea is due to disaggregation of the dye in solution and reduction in dye‐protein hydrophobic interactions. The action of urea in promoting fibre swelling is also likely to be a contributory factor.

Inter nat io nal Wool Secret aria t Technical Centre Valley Drive Ilkley Yorkshire EnglandDuring the commercial operation of chlorine-Hercosett processes, some contamination of the resin solution by sodium sulphite takes place. The progressive reaction between Hercosett 5 7 and sodium sulphite can cause differential-dyeing effects and inadequate shrinkproofing of treated wool. These effects are attributable to a conversion of the cationic sites in the resin to anionic sites. Methods of preventing the development of these problems are described, as are techniques for ameliorating these effects on inadequately-processed wool.

The causes of anomalous results obtained in the measurement of the swelling of wool fibres by different methods have been investigated. The British Standard method (BS 2043) and the fixed‐point method were examined. When urea solutions are used as the swelling media, the results obtained by the two methods differ considerably. The short lengths of fibre used in the BS 2043 method are well within the fibre dimensions for swelling to occur by end penetration and hence give results that can be misleading when related to the swelling of undamaged fibres during processing. When the swelling agent itself can penetrate the fibre wall, either method will give reliable results. When, however, the agent can show colligative osmotic properties typical of many non‐volatile salts, discrepancies may arise between the two methods.

The present aqueous batch processes for the production of Superwash wool are briefly described. These pretreatment/ resin processes suffer from defects such as a harmful effect on fabric properties, a noticeable colour change on treatment and unacceptable cross–staining of multi–coloured materials. The development of aqueous processes in which the polymer is exhausted on to the wool is described in terms of the chemistry of the polymer used and its mode of application, generally by exhaustion from long liquors. The effect on fibre properties is described with particular reference to coloration aspects. Practical considerations that have arisen during bulk trials are covered, together with costings, where relevant.

The importance of control in the application of the water‐soluble polymer, Hercosett 57, to prechlorin‐ated wool tops and garments, is stressed with special reference to its effect on washability and subsequent dyeing operations. Reactive dyes play a vital role in achieving adequate colour fastness to meet machine‐washable specifications and this paper pays special attention to problems of wet fastness encountered with full‐depth dyeings produced with these dyes. In order to overcome these problems, both the dyeing operation and the after‐treatment stage have been closely studied. A novel after‐treatment is proposed as being more effective than the usual dilute ammonia method. Both high‐temperature dyeing and low‐temperature dyeing are discussed, the former method showing advantages in the case of full‐depth dyeings and the latter in the case of pale‐depth dyeings.