MAPLE SIRUP PRODUCERS MANUAL 



77 



PN-4789 



Figure 93. — The dial thermometer, like the tai'get ther- 

 mometer, has markings to indicate O, water boils, 

 sirup, soft tub, and cake sugar. The dial thermometer, 

 like the industrial thermometer, is mounted on the 

 outside of the evaporator. 



PN-4790 



Figure 94. — Sirup at approximately 210° F. is used in 

 making the hot test. The hydrometer cup is raised to 

 eye level and the reading is made as soon as the 

 hydrometer comes to rest. 



Fill the hydrometer cup with boiling sirup 

 from the evaporator or finishing pan (fig. 94). 

 Immediately place the hydrometer in the sirup 

 and, as soon as the hydrometer comes to rest, 

 make the observed density reading. Perform all 

 operations as quickly as possible. If the ob- 

 served hydrometer reading is between 59.3° and 

 59.6° Brix, the evaporation of the sap to stand- 

 ard-density sirup is completed. 



For best results with the hot test, the tem- 

 perature of the hot sirup must be between 210° 

 and 218" F. at the moment the hydrometer 

 reading is made. To be sure that the sirup is in 

 this temperature range, first determine the 

 temperature of the hot sirup as follows: 



Fill the hydrometer cup with boiling sirup. 

 Place the hydrometer and the thermometer in 

 the sirup. Then, instead of i-eading the hydrom- 

 eter, measure the temperature as soon as the 

 hydrometer comes to rest. Repeat this proce- 

 dure and, if the two consecutive temperature 



readings are not obtained in the range of 210° 

 to 218' F., speed up the operation until these 

 temperatures are obtained at the time hydrom- 

 eter readings are made. 



The hot test is not a precise measurement. It 

 is extremely difficult to make accurate hydrom- 

 eter and temperature readings at the same 

 time in sirup that is hotter than 180° F. because 

 the sirup is cooling rapidly. 



Fi-om the time the hydrometer cup is filled 

 with boiling sirup until the observed hydrome- 

 ter reading is made, the sirup will have cooled 

 several degi-ees. The amount of cooling depends 

 on the time involved and the temperature of 

 the air surroimding the hydrometer cup. 



Hydrothcrin 



The hydrotherm, a special hydrometer (chart 

 17), has a liquid thermometer built into it that 

 automatically locates the point on the hydrome- 

 ter (top of thermometer liquid column) for 



