Here is the full pot of sap, as it began to heat. You can see that it pretty much looks like water.
As it boiled down, we added more sap, to keep the pot full. After about six hours, the last five gallon bucket had been added into the boil pot. As it boiled, and the hours went by, the sap began to change color. First getting a little tan, then golden, then amber. About that time, we were down to only about a gallon and a half in the pot.
Since the batch we'd boiled down the night before (I promise a post about that another day) went wrong right about this point, DH wanted to pull the pot off the turkey fryer and transfer the sap to a pot that could be finished on the stove in the kitchen.
So I got out my two gallon pot, put my handy muslin 'sap filter' over the top (secured with a giant rubber band), and DH poured the sap from the big pot into the smaller one. Then I took off the filter, and we put it on the cook top to finish off. I added my candy thermometer in order to keep track of the temperature of the sap from here on out. Syruping point is seven degrees above boiling point.
The 'turbo' burner on my cook top doesn't compare with the newly improved turkey fryer, and my evaporation rate went way down. Where I'd been getting quite a bit more than a gallon an hour on the turkey fryer, it took over two hours to get from about a gallon and a half down to three pints, when it actually got to the syruping point.
I sat in the kitchen, babysitting the sap, and I knit. When I got tired of knitting, I read the farm news. And when I'd finished the farm news, I surfed the web (I'm contemplating increasing the orchard and was researching the best places to get the varieties I am considering adding).
Finally, I saw the tell tale bubbles that indicated the sap was ready to hit the magic temperature and turn into syrup. Note how much emptier the pot is at this point.
From those first syrupy bubbles, it quickly became real honest to goodness syrup, indicated by the golden foam that rose up the sides of the pot.
I removed the pot from the cook top. It was time to can the syrup. I had clean canning jars waiting in a sinkful of hot water, keeping them warm so that there was no chance of the jars breaking when I ladled in the hot syrup.
All in all, it took about ten and a half hours to go from fifteen gallons of cold sap, to three pints of finished maple syrup.