in principle. It consists of a heavily tinned pan strongly made set 

 on an arch which usually has a regular stove front with large doors 

 for firing. The pans have corrugated bottoms and are partitioned 

 off to give a zig zag course to the sap. It is important that it be set 

 quite level so as to maintain a uniform depth of sap. Most of them 

 are equipped with a float feed which allows the fresh sap to flow in as 



Fig. 16. TYPES OF MODERN EVAPORATORS 



All have corrugated bottoms 



rapidly as the water evaporates. The sap enters at one corner usually 

 at the front and by a zig zag course flows from 80 to 100 feet before 

 reaching the outlet at the other end. The sap thickens as it flows 

 and has to remain in the last compartment only a very brief time be- 

 fore it has reached the consistency of syrup. From here it is drawn 

 off at frequent intervals. 



When purchasing an evaporator it is important to provide for 

 expansion of the plant and the taking care of heavy runs of sap. An 

 experienced maker believes in providing ten square feet of boiling sur- 

 face for every one hundred trees tapped. 



