248 Whiter Cover Washes 



their wetting and spreading power and probably the same spreading 

 effect took place in this mixture. By increasing the lime from 20 to 30 

 a thick and firm coat was obtained. This 30, 2, 100 mixture was tried 

 out of doors where it resisted rain fairly well but still did weather 

 somewhat. It appeared therefore that the glue was not made insoluble 

 on the tree quickly enough. Two methods suggested themselves as 

 likely to overcome the difficulty. The first was to use the lime warm 

 and so to get the glue gradually to become insoluble as it dried on 

 the tree. 



This was actually done in one or two cases with successful results 

 but it was found difficult to judge the correct temperature and success 

 was always a matter of luck. Any delay in getting the spray on the 

 tree, owing for instance to choked nozzles, resulted in the glue being 

 made insoluble before it reached the tree and a loss of covering and 

 adhesive power. 



The second method was to use potassium dichromate as had already 

 been done the season before when working with glue mixtures. This 

 causes the glue to become insoluble when exposed to light, thus holding 

 the lime coat together. This method proved quite successful. It is 

 necessary, however, to use the correct amount of dichromate. If 

 too much is used immediate thinning is produced and the mixture 

 is spoiled. If only a little too much is used the lime coat on the tree 

 becomes too flaky though at the same time remarkably hard. So hard 

 is it that if one rubs one's hand on the trunk of a tree so sprayed no 

 lime comes off at all and the surface gives one the impression of fine 

 emery paper. The best quantity to use is expressed in the formula : 



To make this mixture 30 pounds of lime are placed in a tub and 

 6 gallons of water poured over it and allowed to slake. When the lime 

 begins to boil add 2 more gallons of water gradually so as to keep 

 the slaking mixture always as hot as possible. Then 2 pounds of 

 glue are put into a pail with one gallon of cold water and occasionally 

 stirred. After the lime has slaked and become quite cold, which takes 

 6-12 hours, a gallon of hot water is added to the glue which then im- 

 mediately goes into solution. This is then added to the lime, well 



