INTRODUCTION. 9 



evaporation or boiling plant in buckets suspended from a yoke carried 

 over the shoulder. This method has been superseded by a collecting 

 can on a sled drawn by a team (fig. 4), or by a pipe line from the 

 individual buckets, or from stationary tanks placed at intervals. 

 These tanks are high enough to be drained into a central tank at the 

 evaporation house. 



The Indians boiled or thickened the sap by placing it in clay or 

 bark vessels and dropping in heated stones. Sometimes the sap was 

 concentrated by allowing it to freeze overnight and removing the 

 crust of ice. The clay and wooden vessels were later replaced by 

 copper and iron ones. The old lye or potash kettle, which was used 

 for boiling, was suspended from sticks or placed on stones and the fire 

 built underneath it. This method of boiling in kettles is generally 

 practiced at small camps; the kettles are sometimes placed in the open 

 with little or no protection, though a lean-to is often used to cover 

 them. In other cases the concentration of the sap is effected in shal- 

 low pans not over 6 inches deep, of which there may be one or more 

 over the same fire. If one is used, the boiling goes on continuously 

 and generally the fresh sap is added to the boiling sirup. But if 

 several are used, the first sap is placed in the pan farthest from the fire 

 and when sufficiently heated is dipped or siphoned to the next pan, 

 and so on. In this way the fresh sap is not mixed with that already 

 boiling. 



Modern evaporators are constructed on much the same principle, 

 that is, they consist of numerous compartments and the sirup is 

 siphoned from one to the other. The bottom, or floor of the evapora- 

 tor, is corrugated to expose a greater surface to the heat, and parti- 

 tions are placed in the pan to direct the flow of the juice. A constant 

 level is sustained as the sap runs in at one end and, after traversing 

 a distance of about 90 feet or more, is drawn off continuously. Many 

 plants are equipped with steam evaporators which consist of copper or 

 tin kettles with steam coils, in which the final boiling is accomplished. 

 In a very few plants the entire evaporation is effected by steam. The 

 practice in these plants is to reduce the sap to a thin sirup in an 

 evaporator pan or kettle over the fire and then finish the product in 

 steam kettles. As the sap is a nearly pure sucrose solution, normal 

 clarification occurs during boiling, and no other is necessary. This 

 process is more fully described on page 55. 



There is a wide variation in the taste, appearance, and flavor of the 

 product due to differences in manufacture, the greater part of the 

 maple sirup being made on a small scale under varying conditions of 

 care and cleanliness and with the use of different kinds of apparatus. 

 That these varying conditions exist may be proved by comparing the 

 widely differing products seen at the large centers where they are sold. 



