ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 69 
By the inclusion of these four factors, the electrical theory appears 
to explain most cases of dyeing; its value is recognised mostly in 
the case of direct colours where chemical theories have failed. 
Printing. 
The printing of textile fabrics is carried out by applying a viscous 
solution by means of an engraved roller to the fabric. Many interesting 
colloid-chemical phenomena are met with in the preparation of the 
viscous printing pastes. Even to-day there is a considerable amount 
of secrecy exercised in the preparation of these pastes, partly as 
regards the materials employed, but more particularly in the manner 
of mixing them. There is little difficulty in ascertaining the in- 
gredients by chemical analysis, and by the help of colloid-chemistry 
the order in which the ingredients must be mixed can readily be 
decided. Materials which precipitate one another should first be 
mixed with the protective colloid, starch, tragacanth, &c. 
The subsequent fixation of tbe printing colour by steaming, par- 
ticularly in the case of non-mordant dyes, has been shown to be due 
to the swelling of the fibre by the action of the steam.'?**4 The 
fixation of colours from pastes containing both colour and mordant is 
undoubtedly due to coagulation, as the result of reduction in the 
protective power of the colloids at high temperature.°™™"? 3 
Finishing. 
The finishing of textile fabrics is an art to which very ltttle science 
has beenapplied. The effects of the mechanical treatments to which 
fabrics are subjected during finishing! have only recently been 
investigated.? The main factors are mechanical pressure, heat and 
moisture. The effect of moisture is to increase the degree of swelling 
of the fibre, and this is greater the higher the temperature. Pressure 
decreases the swelling in the direction at which it is applied. Per- 
manent finishes are produced by processes which reduce the swelling 
capacity of the fibre colloids. 
(O) Dyeing, 
1 Compare King, First Report, p. 20. 
? Harrison, Journ. Soc. Dyers and Cols., 2'7, 279 (1911), 
3 Harrison, ibid. 34. 97, 127 (1918). 
* Craven, ibid. 34, 128 (1918). 
5 Fort, ibid. 34, 124 (1918). 
§ Haller, Koll. Zeit., 23, 100 (1918). 
(P) Printing. 
Compare First Report Article by Stocks, 46-78, 
1 Justin Mueller, Koll. Zeit., 5, 233 (1909), 
2 Justin Mueller, '7, 40 (1910). 
3 Harrison, Koll. Zeit., 9. 5 (1911). 
4 Haller, Kolloidchem. Beihefte, 8, 1 (1916). 
5 Haller, Koll. Zeit., 23, 100 (1918). 
(Q) Finishing. 
1 See Article in Journ. Soc, Dyers and Colourists, 29 117 (1913) 
* Harrison, Zertile Inst. Journal (1916). 
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