330 



CITY MILK SUPPLY 



From the labor costs and the cost of machinery used, the relative 

 economy of the different methods of washing bottles for plants of different 

 sizes can be determined. The average cost of brush machines was $175 

 and of automatic washers was $1,500 with a 20 per cent, depreciation 

 and with 5 per cent, interest on the investment; the overhead expense 

 at these prices is 12 cts. per day for the brush machine and $1.03 for the 

 automatic. In hand washing the overhead expense would be the upkeep 



Number of Bottles 



FIG. 46. Curves showing the labor and overhead costs of washing bottles by dif- 

 ferent methods at plants of various sizes. 



( Milk Plant Letter No. 18, Dairy Div., U. S. Dept. of Agriculture.) 



of the floor space and is not figured. Taking the wage at 20 cts. an hour 

 the labor cost with each type is determined by dividing this by the num- 

 ber of bottles washed per man per hour in each type which gives 0.00019, 

 0.000585 and 0.00101 ct. for hand, brush and automatic washing respect- 

 ively. With these overhead expenses as an average and this labor cost 

 for each method the graph (Fig. 46) has been constructed. Hand wash- 

 ing is represented by a straight line since the labor cost remains the same 



