MAPLE SIRUP PRODUCERS MANUAL 



55 



first in one position and then in another until 

 all the scale-covered surfaces have been soaked. 

 Sulfamic acid and its salts are toxic to grow- 

 ing plants. For this reason, it is an effective 

 weedkiller. But care should be taken not to 

 discard the used acid solution where desirable 

 plants may be damaged or killed. 



Endrof-Senson Cleaning 



A much-used procedure for cleaning evapora- 

 tor pans at the end of the season is to fill them 

 with sap and let them stand several weeks. The 

 sap will ferment and the acids formed will 

 loosen the scale. If the sap becomes ropy and 

 jellylike, it will be difficult to remove. However, 

 if it is allowed to stand longer, it will again 

 become liquid and can be removed easily. As 

 with the other cleaners, the pans must be 

 rinsed after the fermented sap treatment and 

 dried before they are stored. Fermented sap 

 will not remove heavy scale deposits. 



Whether to clean the evaporator at the end of 

 the sap season is debatable. Some producers 

 store the evaporator pans with the deposit, 

 assuming that this serves as a protective coat- 

 ing and keeps the evaporator surfaces from 

 corroding. The preferable method is to clean the 

 equipment so that it is ready for use the next 

 spring. In either case, the evaporator pans 

 should be dried and stored in an inverted posi- 

 tion. 



Smninaiy 



(1) Use a flue-type open-pan evaporator as the 

 basic unit. 



(2) Evaporate more than 90 percent of the 

 water in the evaporator. The sap should 

 have a Brix value of 45° to 60°. 



(3) Complete the evaporation in a finishing 

 pan. 



(4) To expand the evaporation, add one or 

 more flue pans and operate them in series. 



(5) Operate the evaporator with a minimum 

 depth of sap. Keep the depth of sirup at 

 point of drawoff at V2 to 1 inch. 



(6) Keep sap boiling vigorously at all times. 



(7) For wood fires keep the fire uniform and 

 keep the fire doors closed except when 

 adding fuel. 



(8) If a finishing pan is not used, draw off the 

 sirup as soon as it reaches the proper 

 boiling temperature (7° F. above the boil- 

 ing point of water for that hour and place). 



(9) If a finishing pan is used, draw off the 

 sirup at 45° to 60° Brix (boiling tempera- 

 ture at drawoff 2.5° to 5.1° F. above the 

 temperature of boiling water). Use an au- 

 tomatic valve controlled by a thermo- 

 switch. 



(10) Filter the sirup in transferring it from the 

 evaporator to the finishing pan. 



(11) As soon as the temperature of the boiling 

 sirup in the finishing pan rises 7° F. above 

 the boiling point of water (which yields 

 standard-density sirup; 7.5° above the boil- 

 ing point yields 67°-Brix sirup with better 

 taste), immediately stop heating, cover the 

 pan and withdraw the sirup. 



(12) Clean the evaporators often enough to pre- 

 vent buildup of sugar sand. 



(13) Rinse the evaporator pans with large 

 amounts of water (use three separate rin- 

 ses, draining the pan between each rinse 

 after each time a chemical cleaner is used 

 in the evajwrator or finishing pan). 



(14) Keep the underside of the flues clean. 



OTHER T^ PES OF EVAPORATORS 



Other types of evaporators include the steam 

 evaporator (or a combination of oil and steam) 

 and the vacuum evaporator. 



Stoain Evaporator 



The evaporation of maple sap with high- 

 pressure steam (figs. 84-86 and chart 11) is 

 practiced by a few producers {97). Its use, how- 

 ever, has never become widespread. Steam 



evaporators have several advantages, as fol- 

 lows: (1) The heat is steady; therefore, the sap 

 can be evaporated at a continuous and even 

 rate. (2) Heat can be supplied in steam coils, 

 manifolds, or a jacketed kettle. (3) The evapora- 

 tor can be constructed with smooth walls; flues 

 are unnecessary. (4) Scorching of sirup is mini- 

 mized. (5) The evaporator room can be sepa- 

 rated from the boiler room, which makes it 



