asbestos cloth. (See fig. 3-56.) Continue heating has  reached its proper temperature for  pouring. (See fig. 3-57.) The  temperature of the  zinc  must be accurately measured with a portable pyrometer. NOTE Do not  handle the  portable pyrometer carelessly,  because the millivoltmeter on it is a sensitive, precision instrument. When the portable pyrometer is not in use, keep it in the carrying case. the terminal until it begins to radiate heat waves. Remove the torch from the terminal and leave the terminal undisturbed for 30 seconds. Make a mark on the thickest portion of the terminal with a 550 and 600°F Tempilstik. Repeat this at four areas, 90 degrees apart, to ensure  an average  temperature. NOTE The zinc should be at the proper temperature at this time so that the pouring can take place when  the terminal is heated Prior to  use, check the calibration to the correct temperature. Do NOT attempt to measure term temperature with the portable pyrometer. If the 550°F Tempilstik leaves a wet mark  and the 600°F Tempilstik leaves a chalk mark at the four areas, pour the zinc immediately. If the four areas show a wet mark for both the 550  and 600°F Tempilstik, continue checking the four  areas every 20 seconds until the 600°F Tempilstik leaves a chalk mark  and the 550°F Tempilstik leaves a wet mark; then  pour the zinc immediately. portable pyrometer at  room  temperature. the calibration of the pyrometer as follows: of the Check 1. Place a clean  pouring ladle in  the  melting furnace  assembly and melt zinc in the pouring ladle until the ladle is about one-half full. 2. Heat the zinc to between 950 and  1,OOOOF and measure the temperature with the portable pyrometer. When the temperature has  reached between 950 and l,OOO’F, remove the ladle from the furnace. 3. Immediately immerse the If the temperature has fallen  below 550°F (550°F temperature-sensitive element  of the pyrometer into Tempilstik leaves a chalk mark), reheat the terminal the molten zinc. The pyrometer element must and proceed again as previously described. Skim the dross (impurities) from the top of the molten zinc before pouring. Use  the portable pyrometer to measure the temperature of  the molten zinc  and to determine, thereby, if the zinc remain immersed for the entire calibration. 4. Care must be exercised to  determine the exact zinc freeze point. Carefully observe the pyrometer temperature indicator and the condition of the zinc during cooling. Use a wire probe to check the condition of the zinc during cooling. . HEATINGTORCH HEATTERMlNAL TO%XPF -6W.F Figure 3-56.-Heating the terminal. Figure 3-57.-Pyrometer. 3-58