138 American Milk- Condensing Factories. 
building and its fixtures have been constructed in the most 
expensive manner. 
Fig. 13. — Plan of Third Story of Middletown Milk- Condensing Factory. 
Condensing Skimmed Milk. 
Plain condensed milk is varied in manufacture as follows : — 
I. By using whole milk, or milk containing all its own 
cream, 
II. By mixing skimmed with whole milk. When this is 
done, the skimmed milk is first drawn into the vacuum-pan, 
and after its volume has been reduced considerably, the whole 
milk is added, and the mixture then reduced to thcN required 
consistency. 
III. By condensing the skimmed milk alone. 
At the Middletown factory skimmed milk is extensively used 
for condensing. After the milk has been taken from the delivery 
window and dumped into the heating-tanks, steam is admitted 
to the jacketed bottom, and the milk heated to 130^. A small 
quantity of alum and saltpetre is sometimes added to the milk, 
for the purpose of clarifying it more readily. During the 
heating process the impurities in the milk rise to the surface, 
and are skimmed off, and when this has been effected (the time 
of heating ranging from one and a half to two hours) the milk is 
