14 BULLETIN 894, U. S. DEPARTMENT OE AGRICULTURE. 
The detail of the baffle boxes on the accompanying drawings illus- 
trates a common method of construction. 
No paint should be used on the boxes. 
DOORS. 
The doors should be easily operated, tight fitting, and well insu- 
lated. They should be so designed that slight working due to ex- 
pansion and contraction on account of heat and moisture changes 
will not cause them to stick and bind. A loose-fitting, leaky door 
may cause enough damage in one charge of valuable wood to pay for 
a new door. 
LOADING DOORS. 
Steel, wood, and canvas are the most common materials for load- 
ing doors, but sometimes asbestos on a steel or wooden frame or 
various patent composition doors are used. Steel doors should be 
insulated on the inside with a moisture-proof insulation at least 2 
inches thick. Wood doors are usually built of three thicknesses of 
5-inch stock laid diagonally. Such a door, if covered with tin, is 
practically fireproof and lowers insurance rates. If the door is not 
tinclad, some moisture-proof insulation should be used between the 
plies. Canvas which has been dipped in linseed oil is satisfactory. 
Canvas doors are made double with an intervening air space of about 
a foot, and are hung on rollers. The edges are clamped down when 
the kiln is in operation. 
The doors may be hinged to swing out or built to slide on rollers 
or to elevate vertically by balance weights. Sliding doors can not 
be used where the operating valves and thermostats are on the wall 
between the loading doors of adjacent kilns. Swinging doors should 
be on special or garage hinges and held by refrigerator door locks. 
For the roller doors there are several very satisfactory patented door 
carriers. 
INSPECTION DOORS. 
The frequent inspection of stock and the reading of auxiliary 
thermometers in the kiln is very apt to be neglected unless some easy 
method of getting into the kiln is provided. For this purpose there 
should be a small door in each compartment for obtaining access to 
the kiln without having to open the main doors. Large doors are 
often too heavy for one man to handle and impossible to open or 
close from the inside. Small doors can be built in the main door 
and need not be over 2 feet 6 inches by 5 feet. They should have 
latches or fastenings which may be operated from the inside as well 
as outside of the kiln, so that an operator will not be in danger of 
being closed inside the kiln. 
