MILK-PLANT OPERATION. 23 
economy of using machinery is even more obvious than at that time, 
owing to the fact that the cost of labor is so much higher than it 
was in 1914. According to Figure 16, hand washing was more 
economical than the automatic machine for plants washing less than 
1,200 bottles daily, while the brush washer was more economical 
than the automatic machine for plants washing up to about 2,300 
bottles daily. According to Figure 15 hand washing is not economi- 
cal for plants even of the smallest size, and the brush washer is 
economical only for plants washing 1,600 bottles or less. 
In the illustrations it can be seen that in order to determine ths 
relative economy of the various methods of washing bottles the cost 
of the machine and of labor in the particular locality must be care- 
fully considered. The variation in the efficiency of different men 
must be taken into account also. 
Another factor to be considered in determining which type is the 
most economical is the time required to wash a given number of 
bottles. Time in the milk plant is an important factor, and methods 
of operation must be followed that will provide for the work being 
accomplished in a definite time. It will be noted that at 56 plants 
using automatic washers the average number of bottles washed per 
hour was 4,628, while at 49 plants using brush washers the average 
number of bottles washed was only 928. Thus if a plant has, let us 
say, 5,000 bottles to wash it will take, according to these figures, 
more than five hours with a brush washer, while the work could be 
done with an automatic machine in a little more than an hour. It 
is generally desirable at medium-sized or small plants that the bottle 
washing take no more than half of the day, so that the men doing 
this work can be employed elsewhere during the remainder of the 
day. For example, one set of men may wash the bottles in the morn- 
ing and bottle milk in the afternoon. In that case the bottle washing 
must be done in from three to four hours. It is therefore necessary 
at such plants to select a bottle washer which will permit the work 
to be done in this time, and as a general rule it is to the advantage 
of the dealers handling this number of bottles to use the automatic 
rather than the brush washer. Where only one or two men are 
washing bottles and they are not suitable to help in filling bottles, 
it may be economy to keep them washing bottles for the greater 
part of the day; in that case a brush washer would be satisfactory, 
provided they could wash all the bottles with it in from six to eight 
hours. In any case, however, thoroughness is of first importance, 
and such methods should be used as will result in the most thorough 
cleansing and sterilization. 
In the discussion of labor costs in bottling milk and in washing 
bottles, no attempt has been made to include all types of machinery. 
The studies made include the more common types in use, although 
other more recent types are on the market. 
INSPECTION OF BOTTLES. 
While the large automatic pressure washers give satisfactory results 
in general, there are always some bottles that will not be thoroughly 
cleaned. Bottles that have stood for several days, or those in which 
the casein of the milk has dried, will pass through the machines with- 
out being properly cleaned. It is necessary that all such bottles be 
culled out and washed with a hand brush before they are sent through 
