Flying on thin ice or skating too close to the sun ?

I've been getting decent  amounts of maple sap, thanks to the weather.  But in the first three boils I've had widely varying results:

boil 1: resulting maple syrup was between 32 and 58 brix (brown and sweet but not really syrup

boil 2: syrup was slightly overboiled, brix of 68 (should be more like 66) but close enough

boil 3: syrup was like honey, brix of 80 (couldn't get a good reading), the still breaker flipped off

I just don't have control of my process - in other words: I've lost the recipe.  The sap varies in sugar concentration but I usually boil the same amount at roughly the same starting temperature (refrigerator).  

 

The easy strategy is to underboil and finish the syrup later - but it would be nice to just have a finished product each time without the extra step.

Another strategy would be to dilute the sap to start at the same sugar content each time:  same volume, same temperature, same sugar concentration => same boil time and same resulting syrup,  right ?  

Boiling maple sap in a still is like making candy except not being able to see what is happening.

I'll just have to keep chugging along until I find the right method.

Update Friday: the 4th boil was the same sugar concentration as the 3rd boil, same elapsed time but the result was twice as much "syrup" at a brix below 58, so it might be the ambient temperature in the room as another factor or ?

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm