MAPLE SYRUP AND SUGAR 395 



first comes in from the bush, all the utensils should be thoroughly cleaned 

 and scalded, the sugar house carefully swept and dusted out and the 

 firebox prepared for the fire. The automatic feeder or regulator is then 

 opened and the sap allowed to flow from the storage tank into the evap- 

 orator until it covers all the corrugations. As the sap heats up, the first 

 part to reach the syrup end is dipped back until the proper density is 

 reached. Many of the modern evaporators have a heater in connection 

 with them which warms up the sap from the waste heat so that it evap- 

 orates much more quickly. 



Fig. 105. — Interior of a sugar house showing the steaming evaporator at the left and the 

 " sugaring-off " arch at the right. 



The sap is maintained just as shallow as possible without danger of 

 burning as this method permits the most rapid evaporation. When the 

 fire gets hotter, a greater flow of sap is induced through the regulator, 

 or, if scorching is Hkely, the fire is checked by means of dampers or other 

 patent devices. As impurities or scum come to the surface, they are 

 skimmed off. The sap gradually turns an amber color as it reaches the 

 syrupy stage and deposits of malate of lime (called niter in Vermont and 

 silica in Ohio) are noted on the bottom of the evaporator as the current 

 reaches the end of the pan. Many devices, such as siphons, interchange- 

 able pans, reversing the current, etc., are used to obviate this precipita- 



