Reading Refractometer

[Mattd]

I calibrated my refractometer w distilled water to 1.000sg.

My 1.026sg cal fluid measured 1.018sg. When I adjust for temp (based off the only chart I could find that I could interpret), it is right at 1.026sg.

So, when I measure my permeate it reads 1.000sg, just like the distilled water. Maybe towards the end of a run it bumps up slightly. Do I still need to add .008 for the temp adjustment?

1.008sg is like 2% sugar. That’s a big diff versus 1.000sg and 0%.

[DrTimPerkins]

What is the range of your refractometer? What are you reading in the sap?

Unless the refractometer has automatic temperature compensation (ATC) or you're measuring it at the exact same temperature that you calibrated at, you will always need to compensate. When you take your measurement, make sure that the refractometer and the liquid you're measuring is isothermal (the same temperature) and stable. If your refractometer is warm and the sap/permeate/concentrate is cold, your reading can be off. Let them equilibrate for a min or so. Similarly, if your refractometer is cold and you're measuring hot syrup, it'll be way off. Even if your refractometer is cold, but your hands are warm can throw off the reading.

Permeate often has such low sugar content that it is difficult and unreliable to measure unless your refractometer (or hydrometer) is made to read at low ranges. Just because it'll spit out a number doesn't mean it'll give you a correct number. The better approach is to boil some of the permeate in a pot and reduce it by 50%, take a reading, and double it.

If your permeate is reading 2%, you should be able to taste sugar in it. If you can taste sugar in your permeate...you've got bigger problems than a refractometer.