Sap hydrometer temperature compensation?

[maple marc]

Just picked up a new toy, a sap hydrometer. I plan on comparing trees for high sugar, as well as testing my tanks thoughout the season to see how sugar content changes in general.

When I used it for the first time today, the sap in my tank tested at a fine 2.4 Brix. I then tested a bucket of water from my well, which tested at -.4. The air temperature was 38 degrees, the calibration temperature of the hydrometer. I think the well water was about 55 degrees. I'd like to know if my hyrometer is accurate--that would require a compensation chart. Does temperature effect the numbers? Should my hydrometer read 0 for water at 55 degrees? Anybody know where I can find a chart--if I need one?

Thanks,
Marc

[Maple Hill Sugarhouse]

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[maple marc]

Governor,
Many thanks for your chart. I tested my hydrometer with distilled water at 54 degrees. It read -.5 brix, and with a compensation factor of +.1 my unit is off by .4 brix. That stinks. I hope they will replace it. It came with a certificate of accuracy!

Marc

[Maple Hill Sugarhouse]

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[Gary]

I'am new to "sugaring",i will start next year,still reading, learning,and gathering equipment,in the wait till then. I still haven't read the exact purpose of getting and having a hydrometer,what the purpose is. I have read about having a good thermometer,on why and how to use it in sugaring,so why have a hydrometer? Gary

[Amber Gold]

You use a combination of thermometer and the hydrometer to check the density of the sap or syrup, depending on which you're testing. The hydrometer measures the density and obviously the thermometer measures the temperature. The density of the liquid changes with temperature, so you use the thermometer to be able to refer to a table, which will give you the sugar content of the liquid.

[Gary R]

Governor, thanks for the detailed information on the sap hydrometer. On a PA post yesterday I posed the same question. Adding .1 to my .7%, 54degree birch sap didn't get me excited. But, it's great to learn more about all aspects of this hobby.

Thanks:)

[maple marc]

From my previous post you know I that I tested my sap hydrometer in distilled water and found it off by about .4 brix. I returned it and the retailer kindly replaced it. Well, as soon as the new one arrived I tested that one. Guess what.....it was off by the same amount. I double-checked my procedure...same reading.

I called the manufacturer who asked me to send it directly to them for testing. They sent it back to me saying their tests showed it to be accurate--they tested it twice. I now have what is effectively a certified instrument without the certification. While I don't completely understand their explanations (I talked to two people), here is what I think is going on:

You can't rely on distilled water as a test medium. They don't use water--some other solution. So while my unit reads -.4 brix in water, it is accurate in sap. There is a slight temperature compensation--see the Governor's post below.

They also told me not to worry about the paper scale slipping--it's in there very tight and then glued.

Bottom line--don't get caught up in testing your hydrometer in water--waste of time.

Marc

[Brent]

Every sap hydrometer I've seen so far was calibrated to read accurately at 35 degrees. This is a real world temperature for what you will find it you are checking your sap in the woods or in a storage tank. Sap won't last long, only a few hours, at 55 degrees and nobody will store it at that temp. If your hydrometer is certified it will have the temperature of correct readings marked on the paper inside near the bottom.

It doesn't sound unreasonable to me that if distilled water reads 0 at 35 degrees, then it will be less dense at 55 and give you a reading of something near the -0.4 that you are getting.

[sapman]

I had my sap hydro checked at Bascom's last year. She said it was correct, which pleased me because a friend with a refractometer compared with me and I was high. But when checking my permeate this spring, it usually read a little sugar. So I checked it with distilled water, and got the same reading. I think at Bascom's, they are just checking against another hydro, which is supposed to be right, but who knows.