When I boil down sap for maple syrup I boil it in my kitchen on my stove top. I use a heavy weight stainless steel six quart dutch oven. I set the burner at high till it starts to boil, then turn the heat back just a bit to medium high. As the water boils off, I add more sap from a large kettle that sets on top of the pellet stove in our kitchen. This doesn't boil the sap. It just heats it, takes the chill off of it.
At first the sap boils rapidly and with pretty big bubbles. It looks like water boiling.
As the sap boils down, more sugar to water than what it started out as, the bubbles start to get smaller. It also starts to taste sweeter.
I've never used a candy thermometer when boiling down sap for syrup. I suppose I could but I can't be bothered with that. I do this the same as my father did back when I was a kid growing up in upstate New York and he would tap our maple tree to make syrup. All that sap boiling and steam in the kitchen used to warp our cupboard doors and coat the windows. I crack a window near the stove so that helps out some. But be prepared for a steamy kitchen. Also, don't run off and think you have time to go get involved in something else, something that will take you too far from the kitchen. You need to keep an eye on the sap as it starts to boil down.
After I have used up all the sap from the big pot on the pellet stove, the sap on the kitchen stove starts to boil down in earnest. All this time I have been skimming off the foam that collects near the sides of the pan. These are minerals, etc. No reason to keep all that foam there.
Soon enough the bubbles on the top of the sap start to group up and foam toward the middle of the pot. Taste it again. It tastes even sweeter! Careful you don't burn your tongue. At this point I watch the pot very carefully. Sap, as soon as it hits that critical temperature when it turns from watery sweet stuff to syrup, can get away from you really quickly. I cut the heat back just a bit. The bubbles go back to bigger. When they get smaller again, I cut back the heat just a little more. Taste it again. I watch how it hangs on the spoon. If it coats the spoon and drips off slowly in big drops I pronounce it done. I remove the pot from the burner, let it cool down just enough so I can taste it without burning my tongue, then pour it off into a Mason jar that has been filled with hot water (pour that water out) and sitting on the kitchen counter.
Next day, same thing and I add the new syrup to the old syrup. If there is a day when I will not get so much syrup out of what had been gathered and to boil it down to syrup stage would have left too little in the pot to control the boiling, I don't boil it down to syrup, but save the partway stuff off in a jar and add that to the next day's batch.
This method of pot watching has worked out for me for quite a few years.
At first the sap boils rapidly and with pretty big bubbles. It looks like water boiling.
After I have used up all the sap from the big pot on the pellet stove, the sap on the kitchen stove starts to boil down in earnest. All this time I have been skimming off the foam that collects near the sides of the pan. These are minerals, etc. No reason to keep all that foam there.
Next day, same thing and I add the new syrup to the old syrup. If there is a day when I will not get so much syrup out of what had been gathered and to boil it down to syrup stage would have left too little in the pot to control the boiling, I don't boil it down to syrup, but save the partway stuff off in a jar and add that to the next day's batch.
This method of pot watching has worked out for me for quite a few years.
