Proper procedure for using Hydrotherm

I've had a hydrotherm for a few years now, but never had any instructions as to how to read it and use it properly. Was in the local Co-op the other day, and there was an instruction sheet printed out that was published be Atkinson's Maple Syrup Supplies. There is no copyright notice on it, so I thought I would post the content here.

Description

• The Hydrotherm is a combination of the hydrometer and the thermometer. It measures the density of maple syrup at any temperature between 35F and 210F.
• The scale of the hydrotherm is graduated in 2/10 degrees brix and will indicate the density of the syrup 65.8 degrees brix and thicker.
• The cup for this hydrotherm should be at least 10", preferably 12"

Measuring Method.

• For quicker reading in hot syrup - keep the hydrotherm in hot water. Before use, dry well.
• Fill the cup with syrup and lower the hydrotherm slowly into the cup. Avoid knocking the bottom and sides of the cup. Allow both the hydrometer and the thermometer column to stop moving before reading.
• When the top of the red thermometer column is level with the surface of the syrup, the syrup density is 65.8 degrees brix.
• To comply with Ontario and Canada regulations for minimum density maple syrup (66 degrees brix) the top of the red thermometer column should be 1 graduation above the surface of the syrup.
• When the top of the red thermometer column is 3 1/2 or 4 graduations above the surface of the syrup, the syrup should be near the optimum density of 66.5 degrees brix.
• If the top of the red thermometer is not visible at or above the surface of the syrup, the syrup is too thin.

Hope this helps others - it helped me a lot. I was finishing yesterday and the hydrotherm and my thermometer both agreed at the 66 degrees brix level. To get to the optimum 66.5 brix I had to boil to ~ 8 degrees above water boiling temp.

Sorry for the thread revive.......thanks Big Eddy for this, it's perfect, got a hydrotherm a few years ago but we've never used it as it came with no instructions.
You still using yours?

Can anyone tell me.... how close to syrup do you need to be, to have the hydrotherm start floating at all? I have tried using one a couple times when I'm at 216-217 degrees or so... getting close to draw off, but never actually got it to float at all.... just sat on the bottom of the cup... so gave up and just use the thermometer.... and then when I am drawing syrup, I'm too focused on the temperature to bother with playing around with the hydrotherm.

Fort Wisers - I use mine every time I boil. It's all I use for syrup. The only thermometer I have is still in the box from when I bought it 5 years ago.

When boiling on the evaporator, I watch the syrup and test for sheeting until I feel I am close to ready, then fill my cup. I place the hydrotherm in the cup and see where it floats. I know that if I test immediately, it will float "at the 5th line" when it's syrup, regardless of whether the temperature column has stabilized or not. (basically doing a hydrometer hot test)
If it's ready, I open the valve and draw off about 2l, then repeat the test and see if I continue to draw or stop. On the evaporator I ignore the temperature column completely and just go with where it floats, (because I know where it should float immediately after filling the cup). I draw off a bit heavy deliberately - see below.

When I am finishing, I heat my syrup to 200F-210F, then shut off the heat and float the hydrotherm in the pot. I let the thermometer column stabilize (takes a few mins) and check the density. My target is 66.8 Brix which is 5 lines above the syrup level. Because I draw off heavy, I am usually 8-10 lines over and need to thin. I add 1 cup of sap at a time, stir well and retest - until my density is exactly 66.8 Brix. Then I heat the pot to a full boil, let it cool just long enough stop boiling, and pour it into my filter canner.

wmick - At boiling temperatures (212 - 219) the hydrotherm has the equivalent of approximately 3 Brix of additional stem length before it sinks. So if your boiling syrup is 63 Brix or higher, then it will float. At that point on the temperature density curve, there's about 3/4 degree F difference between 63 Brix and 66 Brix syrup. At lower temperatures, the hydrotherm will float at much lower densities.

The main advantage of the hydrometer and hydrotherm over a thermometer is accuracy. With either, you can measure density to +/- 0.2 Brix. Using a thermometer - even a high accuracy thermometer with 1/2 degree scale- the best you can do is ~1 Brix, and that is only if you accurately account for the boiling point of water TODAY (which will also be off by the accuracy of the thermometer)

Thanks Big Eddy... Appreciate the help.
This is exactly the explanation I was looking for... Makes perfect sense, now, that I couldn't get the thing to float at that point... Wasnt close enough to 66... (and/or too hot)))
Will do some more with it this weekend and hopefully have some success...

Thats really great, thanks Big Eddy!

We check every batch that comes off our evaporator using our hydrotherm. We used to use a refractometer but I didn't trust I was getting accurate and repeatable results in our cold sugar camp.

Now that we have a 2-sided syrup tank we draw off about 20 gallons, slide the empty side of the tank under the auto runoff, stir up the tank of unfiltered syrup, check density using the hydrotherm, adjust the density using permeate to 66.8 Brix, add filter aide and start the filter. We are able to be very accurate with our density with this method.

While it would be ideal to not have to adjust the density we find it is a lot easier to thin the syrup by 0.5 Brix than it is to thicken 20 gallons of thin syrup! We intentionally aim to draw off at about 67 Brix and if it's a hair thinner we are still ok, if a bit too thick we are adjusting down by 0.5 to 1.0 Brix.

Ennismaple and I are doing exactly the same thing, just at a different scale.
He does 20 gallons at a time, I do 20l.
He adds permeate, I add sap.
In both cases we start thick and adjust to exactly 66.8 Brix before bottling.

Embarrassed moment for a “still a newbie”, as I’m reading this and learning more than I knew about using a hydrometer. I always use one to determine when I drawoff, but I’ve only used the top red line (32 Baume / 65.8 brix), and I’m seeing here that all of you boil well past that, so my syrup is thin in comparison. I’d like to understand that. It always struck me as obvious that such a clear indicator as a red line would mean “Syrup”. Is the red line just a starting point, like a minimum acceptable for syrup? Is it just personal preference beyond that? Unless you’re selling in Canada where 66.5 is required? And why would you go beyond that - again just personal preference?

Lifelong learner

One thing to remember about a hydrotherm is they are not certified like a hydrometer. I had one I liked but broke it. got another one but that one would measure a point thin. Moral of story check hydrotherm with something certified to be sure you are getting a accurate reading.I think some places quit selling them for this reason.