46 BULLETIN 894, U. S. DEPARTMENT OF AGRICULTURE. 
The gas-filled type is more sluggish in action than the vapor type, 
out gives the temperature of the bulb only, not being affected by 
higher or lower temperatures along the tube or at the dial. 
The gas-filled thermometers are not affected by the height of the 
bulb so that it is possible to remove the bulbs from the kiln for cali- 
bration in water. The vapor-filled thermometers must be calibrated 
in place. 
Recording instruments have not proved altogether reliable and 
should not be wholly depended upon. They should be regularly 
compared with a standard glass thermometer. Recorders are very 
valuable, however, in indicating whether kiln conditions are steady, 
variable, rising, or falling, making it possible for the operator to 
regulate the kiln from the operating room with a great saving of time. 
Recorders may be obtained in single-pen or double-pen cases, 24-hour 
or 7-day charts, with 8-inch or 12-inch dials. There is no object 
in procuring recording thermometers with a very wide temper ature 
range. In fact, if a chart is selected which will record temperature 
about 20 degrees higher and lower than the highest and lowest tem- 
perature to be used, the divisions on the chart will be wide and easy to 
read accurately. Fifteen feet of flexible tubing is enough in most 
kilns, 
SOME POINTS TO BE EMPHASIZED IN SPECIFICATIONS. 
Gravel, dirt, filings, oil, or other foreign matter in the steam and 
water piping is responsible for much of the trouble experienced when 
starting a battery of new kilns and causes loss of time and expense 
until the system is made clean. Such trouble and expense can be 
reduced, if not entirely eliminated, by careful handling of piping and 
fittings from the time they are delivered until installed. The de- 
signer therefore should take pains to emphasize in the specifications 
the precautions to be taken, and the superintendent should see that 
these precautions are carried out. 
When pipe is being delivered have it piled at delivery on blocks or 
supports free of the ground or floor. Fittings should be kept in the 
gunnysacks in which they are delivered and not permitted to be 
kicked around. 
Both ends of the pipe should be reamed after threading. Before 
assembling, each pipe is to be stood on end and pounded with a 
hammer to remove any scale or dirt. Fittings must be perfectly 
tight, iron to iron, without the use of red lead or cement. 
The water mains should be thoroughly flushed out, with full head 
of hot water, before supplies are attached to kiln. Next, the sup- 
plies to kilns and spray lines should be similarly flushed before 
water mixers or spray nozzles are installed. « 
