354 Winter Cover Washes 



gave sufficient adhesive power but not sufficient covering power. 

 Starch paste was therefore tried to remedy this according to the formula : 



Whiting Glue Starch Water 



8 i i 10 



This gave a thick and fairly firm coat. Less starch gave too thin 

 and loose a coat while more glue became too expensive. In order 

 to get a cheap form of starch, ordinary flour was used after being 

 converted by hot water into paste. 



Three formulas were made up with varying amounts of flour and 

 glue. The results and costs are included in the table below : 



No. 

 (1) 

 (2) 

 (3) 



The price of all these is rather high and they have besides other 

 disadvantages. 



When such a coating is exposed to the action of water it quickly 

 gets washed away owing to the solubility of the glue, but if a small 

 quantity of potassium dichromate is added the glue is rendered insoluble 

 on exposure to light. This action depends on the gelatine of the glue 

 which, mixed with dichromate and exposed to light, becomes insoluble. 



The following formulae were then tried : 



Whiting Glue Flour 

 8 i i 



8 i i- 



8 i i 



8 4 I 



In all cases the addition of the dichromate caused a great thinning 

 in the consistency of the liquid and a poor coat resulted. On trying 

 starch again according to the formulae: 



Whiting Glue 



8 i 



8 4 



good covering power and adhesiveness were obtained in both cases. 

 It was necessary therefore to obtain a cheap form of starch and this 

 was found in "Farina," a potato flour which cost about 2d. a pound 

 when bought by the hundredweight. Accordingly the following two 

 mixtures were tried : 



GIuo Farina Water 



i .! 10 



4 4 10 



