Temp/Hyrdometer Question

[nhmaple_enthusiast]

Hello
I set 35 taps in northern NH and boil down on a Smoky Lake 2'X4' flat bottom pan that is divided. Nice little rig for # of taps. Because my sugar house is not close enough for water and power I try to bring it close to syrup and finish it in the house on an electric cooktop. I use a digital thermometer and hydrometer to finish. I test the thermometer in boiling water prior and because I'm 1100 feet above sea level I expect the thermometer to show water boiling at 210 degrees. One degree less for each 500 feet of elevation. And it's accurate and shows water boiling at 210 degrees. I would then expect to be close to syrup at approx 217-218 degrees, but that is not the case. I cannot get the hydrometer to float at the hot line unless I'm at a strong 220 degrees. I fill the hydrometer cup right out of the kettle and it's very close to the 211, maybe slightly less.
Maybe I'm splitting hairs here but it seems that I need to be well above the 7 degrees. Just wondered if anyone has experienced similar issues
thanks Tim

[ecolbeck]

The boiling point of water is also affected by weather induced barometric pressure changes. The exact boiling point of water needs to be determined on a daily basis. The other thing to consider is that you need to compensate for temperature with your hydrometer. Manufacturers make temperature compensation charts to help you determine the correct density at a particular temperature.

I actually set my thermometer based on the finished density of syrup rather than boiling water. I find this method more convenient. I also draw off syrup slightly over density and then dilute it before bottling. It is far easier to dilute syrup than it is to reheat and continue boiling.

[RedMapleCreek]

I used to have the same difficulty in knowing what hydrometer reading was syrup for a given temperature during the sampling. I now use a Murphy cup which has a built in dial thermometer that indicates the correct hydrometer reading for the temperature of the contents in the cup. This eliminates any need for temperature compensation charts and makes checking tHe density quick and easy. I bought mine at Bascoms, but they are available from several maple equipment vendors.

[ecolbeck]

I used to have the same difficulty in knowing what hydrometer reading was syrup for a given temperature during the sampling. I now use a Murphy cup which has a built in dial thermometer that indicates the correct hydrometer reading for the temperature of the contents in the cup. This eliminates any need for temperature compensation charts and makes checking tHe density quick and easy. I bought mine at Bascoms, but they are available from several maple equipment vendors.

+1 on the Murphy cup. Makes life MUCH easier.

[bill m]

First, are you sure your hydrometer is correct? If it is then stop worrying about temperature and trust the hydrometer. Just make sure you are using it correctly.

[M&M Maple Grove]

It’s also worth noting that the hot test line on a hydrometer is an estimate. Hydrometers are calibrated at 60° Cold test line. Overtime, I found it a lot easier studying how to syrup comes off a scoop or metal spatula after dipping and removing it from the syrup. The viscosity of the syrup as it is running off is the best indicator for me. The old timer method. If you were finishing off on the stove top, you can check with a hydrometer at 60° and make a good estimate of where you’re finishing point will be in the pot. I’ll use the hydrometer to get an estimate of where I’m at while finishing but the line never seems to be accurate. Refractometers are handy as well. Much less chance of breakage.

[bill m]

Overtime, I found it a lot easier studying how to syrup comes off a scoop or metal spatula after dipping and removing it from the syrup. The viscosity of the syrup as it is running off is the best indicator for me.

Of all of the methods of testing syrup this is the least accurate. I have demonstrated to visitors many times how it will sheet off of a scoop and then check with a hydrometer and it will not float.

I’ll use the hydrometer to get an estimate of where I’m at while finishing but the line never seems to be accurate.

What are you using to check it against to prove your hydrometer is not accurate?

[nhmaple_enthusiast]

Thanks for all the replies.....here is why I brought this up. When I first started sugaring many years ago I used Rink Mann's Backyard Sugarin' handbook as a guide. Neat little book for the beginner. This was before Murphy Cups and Rink used a thermometer to determine when his sap was syrup, no hydrometer. He checked his thermometer in a pot of boiling water next to his kettle and added 7 degrees. That's exactly what I did, but because my water boils at 210 I checked it at 217 with a hydrometer and it was just barely floating. So I thought maybe the 7 degree concept was just a guide. But if I red line at 220+ then I'm thinking either the hydrometer is way off and my syrup is way heavy or forget about the 7 degree concept.
My Bascom's hydrometer was bought quite a few years ago, but when I got it I used my vernier caliper to measure the top of the paper to the top of the glass bulb to gauge whether it has moved over the years and it has not. it's still at .885
I'll probably pick up another hydrometer at some point. thanks again

[DRoseum]

You have to use a hydrometer, a thermometer and a compensation chart OR a hydrometer and a compensation (murphy) cup. Density changes with temperature - you have to account for that to make sure your density is correct.

Also as others have noted, the finishing temperature of syrup (and boiling point of water) can vary by multiple degrees F based up current barometric pressure at your location. I have had it change by 2 degrees mid boil. Hydrometers (if in good condition and used properly) are best for density checks. State regulators who inspect your facilities and practices will want to see a controlled process/procedure for actually measuring and documenting density for each batch if you plan to sell your syrup.

[Sugar Bear]

Hello
I set 35 taps in northern NH and boil down on a Smoky Lake 2'X4' flat bottom pan that is divided. Nice little rig for # of taps. Because my sugar house is not close enough for water and power I try to bring it close to syrup and finish it in the house on an electric cooktop. I use a digital thermometer and hydrometer to finish. I test the thermometer in boiling water prior and because I'm 1100 feet above sea level I expect the thermometer to show water boiling at 210 degrees. One degree less for each 500 feet of elevation. And it's accurate and shows water boiling at 210 degrees. I would then expect to be close to syrup at approx 217-218 degrees, but that is not the case. I cannot get the hydrometer to float at the hot line unless I'm at a strong 220 degrees. I fill the hydrometer cup right out of the kettle and it's very close to the 211, maybe slightly less.
Maybe I'm splitting hairs here but it seems that I need to be well above the 7 degrees. Just wondered if anyone has experienced similar issues
thanks Tim

Be sure to read this a couple times because I am not a good writer/explainer, but it will probably manifest the cause of your confusion and misread of temperature.

Your hydrometer is calibrated to float "syrup" at the red line at the 211 hot reading because that is the "anticipated" temperature of what syrup will quickly/soon be in the cup when it is poured at 219 degrees into the 68 degree cup ( cup that is stored at typical room temperature) .

The hydrometer is calibrated by the maker ( thermodynamic engineers ) and they assume the cup is calibrated to 68 degrees or there about by the user.

So you have to ask yourself, what is the temperature of your metal cup when you poor syrup into it? Are you pouring syrup into a 60 degree metal cup?
In which case your syrup might need to be at 220 before it will show up at 211 in the cup.

As we all know metal quickly and effectively cools hot liquids and visa versa.

So if you store your cup at 32 degrees and then pore 219 degree syrup in it, it will immediately be something like 204 degrees in the cup. And that will give you an inaccurate reading. 210 degrees will give you an ever so slightly inaccurate reading.

If you fill your cup once with 219 degree syrup ( you will heat the metal of the cup up some ) and then pore syrup out and quickly refill immediately with 219 degree syrup you will have syrup in the cup that is 214 degree. Again producing a inaccurate reading on the hydrometer.


Again ... a metal cup stored and at 68 degrees filled with syrup at 219 degrees should result in syrup in the cup at 211 degrees immediately and then falling from there.

A 78 degree metal cup will do something different temperature wise.

So will a 32 degree metal cup.

The permutations and combinations are endless.

But if we are careful with our cup temperature, hydrometers will work very well so long as they are calibrated to begin with well. Which can be another issue in itself.

The bottom line here is that the manufacture has to calibrate the hydrometer well and the user has to calibrate the temperature of the metal cup well in order for them to be accurate.