FIXING OF COLOURS.

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quite free from particles of those membranes which line the inside of theshell> the solution of albumen should always be carefully filtered through afine silk sieve, because the presence of small solid particles in the solution,although they may be so small as to be invisible to the naked eye, causesdefeats of a serious nature in the printing, viz., the production of dark colouredspecks upon the cloth.

Albumen of good quality is recognised by its transparency when in flakes,by its taste being not disagreeable, and the odour free from that of putrefaction;it should dissolve readily in cold water with constant stirring. To preventfrothing, and to render the albumen smooth in working, as well as to preventputrefaction, various additions are made, the material added being probablynot the same in any two places. Ammonia, turpentine, and oil are amongthe principal agents added, but the quantities must be very small. A solutionof white bees’-wax in olive oil is sometimes advantageous; bees’-wax and notJapan-wax should be employed. M. Zeller states that good results areobtained by the addition of a certain quantity of fine olive oil to the drypigments previously to mixing them with the albumen solution ; when, forinstance, to 2 kilos, of ultramarine 500 grms. of oil are employed, the colour,after fixing, will be at least 10 per cent deeper; and it follows that a smallerquantity or an inferior quality of material may be used. In technical termsthe colour “goes further;” while there is the very considerable advantagethat after the dressing of the goods they are much more flexible* and muchsmoother than when oil has not been added. In order to obtain good resultsin cylinder printing it is frequently necessary to add gum to the albumencolours.

A solution of albumen cannot under ordinary circumstances be expeCtedto be long kept free from putrefaction ; and true antiseptics have a coagulativeeffect. It is therefore usual to employ oil of turpentine, which is added withthe twofold view of preventing frothing as well as putrefaction. Hyposulphiteof soda has been used, but with no good effeCt. But arsenite of soda, orarsenious acid, commonly known as white arsenic, in the proportion ofT^th part by weight of the albumen, is not injurious to the colour, and,according to M. C. Kcechlin, a high practical authority, the best preservativeof albumen solutions.

The following substitutes for albumen have been proposed:—An ammoniacalsolution of shellac for the fixing of ultramarine. Copal first softened inaceton, and then dissolved in essence of lavender; fabrics treated with thissubstitute may be washed in even boiling water. A solution of caoutchoucin coal-tar oil, petroleum, or Persian naphtha has been successfully employedfor fixing ultramarine upon woollen stuffs; the method answered well, buthas been abandoned on account of the inflammability of the solution, andprimarily on account of the discovery of the aniline colours. A solution ofresin in linseed oil has been substituted for albumen, as well as gum sandarachand mastic dissolved in acetic acid, the latter not being employed with suchpowdered colours as ultramarine.

In order to ascertain whether a colour is fixed with albumen, or with any°f its substitutes, the fabric should be momentarily immersed in boiling soap-suds and slightly rubbed: well-fixed albumen pigments withstand thistreatment, but where substitutes are employed the colour scales off.

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