396 FOREST PRODUCTS 



tion. It is estimated that on the average evaporator used, the sap covers 

 about 50 ft. of surface through the various compartments before it finally 

 emerges as syrup. 



It has been determined that sap boils at 213 F. At 219 F. (at 

 500 ft. in elevation above sea level) the syrup will have attained a specific 

 gravity of about 1.325 and weigh n Ib. to the gallon, a point at which it 

 will not granulate. At the beginning of the season sap ordinarily con- 

 tains about 6 per cent of malate of lime; later in the season it may con- 

 tain from 25 to 30 per cent of the total dry matter of the sap. If the 

 malate of lime is not removed before the syrup is taken off, tempera- 

 tures should run about 221 F. An increase or decrease in the altitude 

 of 500 ft. affects the thermometer i F. for the purpose of boiling. 



Every few minutes the syrup is run off and strained through felt to 

 remove any malate of lime not already eliminated or any impurities of 

 any kind. It is then put up when still hot into tin cans or glass jars, the 

 former usually of i or ^ gal. size and the latter of i or 2 qt. capacity. Care 

 must be taken to observe that the containers are absolutely clean and 

 when filled are made airtight and kept in a cool place. 



When sugar is to be made, the syrup is placed over the sugaring-off 

 arch and heated until it is so thick that it pours slowly or becomes 

 waxy in the snow or in cold water. This occurs at a temperature of 

 about 230 F. It is then turned into molds. Experienced sugar 

 makers can readily tell when the syrup has sugared-off, but some operators 

 use a saccharometer or thermometer to determine this. When hard, the 

 sugar is wrapped in wax paper. The first run of sap always makes the 

 best sugar. In fact, that from the last of the season will sometimes fail 

 to " cake." 



YIELDS OF SAP, SYRUP AND SUGAR 



The yield of products in this industry varies considerably with the 

 season, size of the tree, character of tapping and many other conditions 

 which have been covered under the subjects of sap flow, tapping, etc. 

 Yields are often expressed on the basis of the individual tree. However, 

 this is not a satisfactory basis, because much depends upon the size of 

 the tree, the number of buckets hung, its past and present condition, etc. 

 A general figure for all trees, an average of 3 Ib. of sugar per season per 

 tree is sometimes used. This varies, however, from i to 7 Ib. per tree. 



The most satisfactory basis of determining the yields is expressed in 

 terms of the individual bucket. Both costs and yields are now coming 

 to be expressed in terms of buckets rather than the individual tree. By 



