MANUFACTURE OF CASEIN. 11 
stacked trays freely through it. Many tunnels are made -31 or 32 
inches wide to accommodate the 30-inch-square drying trays which 
can be purchased ready-made. The tunnels used in our experiments 
were 24 inches wide (fig. 2). A double-tunnel drier, 22 feet long, 
5 feet high, and each tunnel 24 inches wide, when filled with drying 
trays will hold the casein from 20,000 pounds of buttermilk. The 
driers can be made of any length and height but it is advisable to 
have them high enough to allow a man to walk in without incon- 
venience when pushing the trays in or out. Full-width doors are 
placed on each end of the tunnels, so that the trucks stacked full of 
trays may be pushed in at one end and out at the other, which facili- 
tates and systematizes the work. The cost of a drying tunnel can be 
ascertained by considering the type of construction and the price of 
material and labor available in the locality. 
BLOWER AND HEATING APPARATUS. 
A low-pressure blower of sufficient capacity to provide a large 
volume of heated air over the ground curd is required. No exact 
figures as to the cost of a blower can be given. Gne of the casein 
jobbers quotes a price of $35 on a blower and $50 for a heater which 
has sufficient radiating surface to heat the air to the required temper- 
ature. The additional expense of installing the apparatus, supposed 
to have a capacity for drying the casein from 15,000 pounds of milk 
daily, should also be considered. It may be possible to make a pipe 
heater at the factory more cheaply than it can be purchased, but if 
the best results are "to be obtained care must be taken to have the 
proper radiating surface. 
DRYING TRAYS AND TRUCKS. 
Satisfactory drying trays of the desired size can be made of J-inch 
square strips and galvanized screening. A rectangular frame is made 
of the strips, which are mortised and glued at the corners. Another 
strip is mortised lengthwise of the frame. Galvanized screening, 
16 meshes to the inch, such as is used for windows and doors, is 
tacked to one side of the frame, after which ^-inch by J-inch strips 
are placed over the screen, flush with the lengthwise strip, and fas- 
tened with screws. The three strips forming the bottom of the tray 
allow a free circulation of air through the stacked trays, and in 
addition materially strengthen it. Canvas or unbleached muslin 
used on the bottom tray of each truck, in place of the screening, serves 
to catch the fine particles of dried casein that drop through the 
upper trays. With galvanized-wire screening at the prices that 
prevailed in 1914, when the experimental equipment was installed, 
the 23 by 30 inch trays may be made for $7 a dozen and the 30 by 30 
inch trays for about $9 a dozen, 
