7 Degrees? Science Question

[OneLegJohn]

I have a few questions for you fellow traders this morning. This one is in regards to properly using my new auto drawoff. Here goes the first question. Keep in mind I have a 2X6 evap and boil 10% concentrate.

After bringing the temp of the drawoff from startup mode to production mode (increasing from 6 over by tenth degrees) I was still drawing off light. BP of water was 210.4F and I eventually set the drawoff to 217.4F, 7 over. The hydrometer said I was light. I kept increasing drawoff temp until I hit 218.2 and just decided to finish in finisher. Shouldn't the two coincide, Temp and density? Which one is more accurate? Do I set the drawoff to 7.5 or 8 degrees over BP of water? What the heck is going on?

[wnybassman]

For ten years I was finishing my syrup at 7º - 7.5º over. Last year I bought a hydrometer and find myself having to go 8.5º or so over now to get the density right.

[peacemaker]

have u had your hydrometer calibrated

[Toblerone]

I have the same experience, with a brand new hydrometer. I don't know the exact temperature elevation, but it is always more than the 7.1 they say you need. I think the hydrometer is the more accurate since it measures density directly.

[Tweegs]

Ditto Peacemaker.
Ours reads .5 low.

[Brent]

I've used two different auto draw off devices and neither one could be set by the displayed number, even though they were barometric compensated.

I learned to set them low, draw, test and bump up 1/2 a degree and keep that going until I got the test to give me the best results. Almost always a degree or more above the magic 7. Now I really don't care what the display says.
Once set up to give the right density, they repeated pretty well. U think the angle of the probe into the syrup can change the numbers. I have also found that poor handling pulled the sensor up inside the tube a couple inches, so even though the tube seemed well submerged, the sensor was not.

[OneLegJohn]

When you draw off light, what do you do with it? Do you pour it back in the opposite side of the syrup pan?

[forester1]

No, I wouldn't pour it back to the opposite side of the pan. You will upset your gradient. I would pour it back to the drawoff channel, maybe back a little from the drawoff.

[OneLegJohn]

Thanks, Jerry. There hasn't been clear instructions as to where to put it.

[ToadHill]

Be very careful pouring unfinished syrup back into your syrup pan. Add it back in small quantities between draws. We once poured a bunch back into a 5x16 rig and ended up with so much syrup in the pan that we couldn't get it out fast enough and scorched the pan.

As for the hydrometer and thermometer/auto drawoff accuracy, hydrometers are the more accurate method. They are inspected by the State of Vermont before they are sold, but you should periodically calibrate it against one that you know to be correct.

The problem with thermometers is twofold; first they can be off by as much as 3-4 degrees right out of the box and when you combine that with an uneven heat source you can get pretty dramatic errors. When checking the boiling point, if you are off by one degree Fahrenheit that is the equivalent of 3 brix. So say your thermometer says it is syrup, but it is off by one degree, then instead of 67 brix syrup you have 64 brix. With a hydrometer you can avoid this, but you will need to use a correction chart if you want to use the hydrometer at any temperature other than what they are calibrated for (usually 211 degrees and 60 degrees). Hydrometers are really easy to use and are highly accurate. Just make sure you keep it clean (nothing stuck to the stem) and read across the top of the syrup and not the top of the meniscus.

With an automatic drawoff you should check the density with the hydrometer and set the drawoff at whatever temperature gives you the correct density and disregard the temperature since it is actually irrelevant.

Hope that helps

[OneLegJohn]

Hope that helps
Yes. Yes, it does. I use a hydrometer, but I don't have a way to check temp in the hydro cup. Why would the Marcland autodrawoff have a 3-4 degree variation?

[Sugarmaker]

Nate,
I calibrate my auto draw off with my hydrometer as mentioned.
I feel that the hydrometer is more accurate than the temp.
Most of the time our Auto draw is set to draw off at about 217 F. Once that is set I still check with the hydrometer once in a while during a long boil.
Chris

[Haynes Forest Products]

Hydrometer is effected by Atmospheric pressure and the drawoff isnt. Did you account for that.....................I NEVER DID I always went by the hydro:)

[peacemaker]

sit at bascoms on open house day with the lady testing hydrometers and u will see that even brand new ones all test differently

[Bucket Head]

I have commented before on how the seven degree's over the boiling point is incorrect. Just one of the many things learned the hard way, unfortunately.

My question is where did the seven degree standard come from? Who determined this? How did they determine this? And why is it still printed in every sugaring publication when its widely known to be wrong?

Steve

[Brent]

I don't think the number is wrong, I think it's a matter of the instruments we're buying .... generally the cheapest we think will work.

Thermometers have the largest degree of error. I have a collection digital thermometers, two on draw offs and one stand alone that are barometric corrected, and a couple from the wife's kitchen, and several old style ones. Put them all in a pot and very few, if any agree.

Then you get the imersion factor. Are you measuring very close to the pan where there might be more liquid, or are you measuring up in the foam and bubbles.

Then try to get your hydrometer to agrees with a digital refractometer.

I think the standard 7 or 7.4 or whatever is more likely to be correct than any of our instruments.

[BryanEx]

What can be determined in a lab is often difficult to reproduce in practice. Who here actually gets the mileage their car or truck manufacturer claims? My Honda Civic is good on gas but does not achieve 55 mpg on the highway as advetised.

[red maples]

Different times of year possibly different grades as well. Last year the begining of the year I could draw off at 219 exactly at the #7 on the dial but about the 1/2 mark of the season I had to keep drawing off at a higher temp. On any given day I monitor with the hydro until I can draw check it against the temp on evap and draw at that temp I will recheck sometimes but it will work for that day. There were days last year I had to let it go almost to 221* to drawoff that almost 9*.

[Beweller]

The elevation of the boiling point is determined by the content of dissolved substances. I suspect that the usual 7.4 degrees refers to dissolved sucrose. In maple syrup there will be other sugars--of lower molecular weight-- other organic substances of lower molecular weights and dissolved minerals. All of these will affect the boiling point while having a smaller effect on the density.

I doubt that many maplers have precision temperature measuring equipment. My experience with electronic cold junction compensators--while acquired some years ago--was not encouraging. ASTM precision thermometers are expensive and easily broken. Ice junctions can easily be 4 degrees C off if the ice is allowed to float. And on and on.

[Haynes Forest Products]

Beweller very intresting about the solids. So I drawoff and filter into my finisher and then tweak it to the right density. I also hear from the real sugar makers that test the syrup a the draw off filter into the bottler and bottle. SO im thinking my way is the more acurate way because I test my syrup with a hydrometer AFTER the solids are removed:)

[Beweller]

Suspended solids do affect the density. This is used in one technique to determine the clay/??/sand content of soil. (A senior moment--I can't come up with the word where the ?? appear.)

But to affect the density by say 0.01, you would require 10 grams of suspended sugar sand per liter of syrup. Not likely.