Like well water, maple sap contains minerals. When boiling, you’re depriving the sap of water but the minerals and sugar remain. The sugar density increases and the minerals concentrate. The absence of water causes the minerals to drop and bake on the floor of the pan. This is most severe in the last compartment of the evaporator, the compartment where you’re drawing finished syrup off of.
As your boil time progresses the minerals, called “sugar sand” or “nitre” in the maple world, become so thick in the draw-off compartment that they become problematic. The sugar sand will bake on so thick that the heat from the fire is able to damage the pan because the liquid isn’t able to cool/protect it. Eventually sugar sand will begin to flake off in huge pieces which can clog valves and plumbing.
Sugar sand must be mitigated, either by cleaning the pan often or by reversing the flow. Reversing flow of the pan has become a popular method of dealing with the issues caused by sugar sand as it takes less time and is less wasteful than cleaning. Smoky Lake Pan Sets are reversible by disconnecting the front pan and rotating it 180°. Alternatively, the Same Side Reverse (SSR) option on Smoky Lake Pan Sets allows you to reverse the flow simply by swinging the handles of two stainless steel ball valves. It is the easiest system in the industry.
Methods of Reversing
There are two different styles for reversing the flow. One style requires you to turn the pan 180º on your arch (see video below for details). The other style of reversing is called “Same Side Reverse” (SSR). The SSR system allows you to change the flow direction by simply swinging the handles on two valves. The SSR system is available on Smoky Lake Drop Flue Pan Sets and Raised Flue Pan Sets.
Below are the instruction guides for various Smoky Lake pan styles. Within each guide there is a section regarding how to reverse the flow and/or remove sugar sand. Please note that Flat Pans and Hybrid Pans are not reversible. For those styles pans, simply drain and clean the pan in order to remove nitre.