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How To Use A Murphy Cup Or Float

The first thing to understand is that hydrometer readings are affected by two things:

  1. The Sugar Density
  2. The Temperature of the Syrup Sample

The reason your hydrometer has two different “finishing lines” on it is due to the temperature variable. One line represents the “Cold Test” (60ºF) and the other line represents the “Hot Test” (211ºF). Both of those lines are telling you where the syrup should float if you have perfect density (66.9º BRIX). But what do you do if your syrup is any temperature other than 60ºF or 211ºF?

Before the Murphy Cup, sugar makers had to take the temperature of the syrup sample with a thermometer and then reference a compensation chart to calculate where the hydrometer should be floating if it is 66.9º BRIX. All the while, temperature of the sample could be changing, and temperature was a moving target. The Murphy Dial simplifies the process so that your regular thermometer and compensation chart are no longer needed.

The Murphy Dial displays your TARGET — or the “finishing line” — that your hydrometer must match. Use your hydrometer reading to determine if your sugar density is higher or lower than the target.

If the hydrometer and dial readings match, the syrup is perfect density (66.9º BRIX).

If the hydrometer reading is LOWER than the dial’s reading, your syrup’s sugar density is LOWER than 66.9º BRIX.  Therefore, keep boiling.

If the hydrometer reading is HIGHER than the dial’s reading, your syrup’s sugar density is HIGHER than 66.9º BRIX.  Slowly stir in distilled water or sap to reclaim perfect density.

Downloadable Instruction Sheet

How To Read A Murphy Dial
How To Read A Murphy Dial


Hydrometers and Cups by Smoky Lake

  • Maple Syrup Hydrometer $26.00Add to cart
  • GOLD SERIES Maple Syrup Hydrometer $38.00Add to cart
  • Murphy Compensation Cup $149.00Add to cart
  • Murphy Compensation Float $149.00Add to cart

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4 Comments

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Susan Andrews

March 19, 2022

hi there, I love the Murphy Cup and am using it right now to check density of my current batch of syrup.

Main question is, how long do you have to wait a dead-on accurate reading? I’ve been checking it every 10 minutes (20 min now) and the hyrometer’s reading keeps changing as the syrup cools. Currently it looks like I am with .5 of density but would like it be dead on.

Any ideas as to how long I should wait, please let me know!

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Angela

March 19, 2022

Hi Susan
The dial is going to change based on your syrup sample’s temperature. The temperature is going to change the way that the hydrometer floats, which is why the Murphy Cup is so important. You do not need to wait for your sample to cool. You may compare the dial reading to the hydrometer reading at any temperature.

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Rich

February 16, 2023

I got one of these for Christmas and I still don’t figure what the hype is. When I fill my Murphey cup as my sap is within a degree of being syrup, it takes 10-20 seconds for the dial to stop moving. I know my temp is between 218 and 219 because I have a thermometer set up in my divided pan. So let’s say today sap is syrup at 219. When the alarm goes off, I scoop a ladle out and dump it in my cup with the hydrometer to verify what I already know. Those 10-20 seconds I wait for the murphy cup to settle, I could end up with sugar. I think Susan above may be on line with what I’m saying. I can’t find a video so I don’t understand what the hype is about a MC.

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Angela

February 16, 2023

Hi Rich. You would be surprised how fast syrup cools when it is placed in a test cup. For example, you see visual evidence of this because you know that the syrup never continues to boil in a cup. That’s because it is cooling rapidly. The fact that the dial on the Murphy Cup is moving is further evidence that the temperature is changing. This is why trying to use a thermometer and compensation chart is so excessively tedious and frustrating when the temperature is changing. The Murphy Cup takes this all in stride. At any moment in time, you know where the hydrometer should be floating based on the current temperature of your sample.

You can learn more about using a Murphy Float in our Barrel to Bottle series. (The Murphy Float and the Murphy Cup operate via the same fundamental concepts) https://www.smokylakemaple.com/barrel-to-bottle. See session 1 regarding density checking.