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What is a Refractometer?

Refractometers are handheld, lightweight, portable instruments used to determine the concentration of water soluble fluids such as machine tool coolants, heat treating fluids, hydraulic fluids, plating baths, detergents, antifreeze, battery acid, etc. The BRIX scale was actually developed for working with sugar related liquids (fruit juices, soft drinks, wine), but it is also commonly used for controlling the concentration of various industrial fluids (cutting coolants, glycol solutions, and flux rinsing compounds).

Refractometers are very easy to use, even the non-digital, analog refractometers. Just place a few drops of fluid on the prism and hold the unit up to a light source. Look into the eyepiece and read the scale. To calibrate, just make sure the prism is clean and place a few drops of tap water on the prism. The separation line should be on zero. If not, turn the adjustment screw until it is.

Remember, refractometers read on a Brix scale rather than actual percent. To get the actual percent, you must multiply the refractometer reading by your coolant's refractive index (on product data sheet). With most soluble oils the index is 1, so a refractometer reading of 5 multiplied by an index of 1 = 5% concentration. However, many semi-synthetics, synthetics, grinding fluids, and some soluble oils can have a refractive index from 1.5 to 3. So a refractometer reading of 5 multiplied by an index of 1.75 = 8.75% concentration. This is most critical with solutions designed to be run at lower concentrations which have high indexes.

Another often ignored but very important factor is the difference between "working" concentration and "make-up" concentration. The fluid in your tank is the working solution and should be at the recommended concentration. But when adding make-up fluid to the tank, you must allow for evaporation of the water over time from the working solution. Typically the make up should be added at 1/2 the recommended "working" concentration. But there are many variables which affect this relationship, and every machine in the shop will be different. So the best course of action is to monitor the fluid in the tank with a refractometer and adjust the make up fluid leaner or richer to maintain proper working concentration in the tank.

Maintaining the proper concentration of your cutting and grinding fluids can save you money! First, you'll eliminate "rich" solutions that waste coolant, leave sticky/oily residues, and possibly cause operator health problems. Second, by eliminating "lean" solutions, you'll extend tool life, limit biological growth, and reduce machine and parts corrosion problems.

Misco Palm Abbe Digital Refractometer
Misco Digital

The new Palm Abbe is a fourth-generation digital handheld refractometer that puts laboratory precision in the palm of your hand. Not just laboratory precision, but laboratory precision for the price of a traditional analog refractometer. It is exactly the kind of bold, cutting-edge technology you would expect from MISCO, the company that pioneered the digital handheld refractometer.

The Palm Abbe refractometer is fast, convenient, and easy to use. Simply place a drop or two of fluid in the well and press a button on the key-pad. The custom-designed microprocessor delivers a nearly instantaneous readout in refractive index, degrees Brix, or any one of a thousand different units of measure, allowing you to read directly in the units you desire. Nonlinear temperature compensation is automatic and insures that fluids read between 0 and 50 °C (+32 to 122 °F) are measured accurately.  Nonlinear temperature compensation is more accurate than the (linear) automatic temperature compensation (ATC) on analog refractometers.

The large dual-line LCD display is easily read, even in dim light, and removes the subjectivity associated with interpreting where a boundary line crosses tiny scale divisions. And, it is so easy to use! The user interface consists of two buttons, one to take readings and the other to step through various menu options.

Calibration is automatic and does not require the use of special calibration solutions or tools. The Palm Abbe refractometer automatically calibrates itself to water and is ready to use in seconds. No more screws to turn and nothing to adjust.  If you need NIST Traceable Certified Calibration, it can be ordered under Misco Palm Abbe Accessories below.

Analog Industrial Refractometer
Laxco Analog

Quality new style refractometers, not the old style. Steel and glass head and prism. These are the INDUSTRIAL Series which feature rugged, drop-tested daylight plates, magnified scales for precise readings, and all-metal construction, which make these handheld refractometers an exceptional value!  These analog refractometers are backed and inspected by Laxco, formerly Westover Scientific and Advanced Microscopy Group (AMG).

NOTE:  Analog refractometers can be easily calibrated using tap water.  However, they cannot be ordered with calibration certification papers.  If you need NIST Traceable Calibration Certification, then you must order a Misco digital refractometer.

Misco Palm Abbe Digital Refractometer Rubber Jackets

Misco Palm Abbe Cases, Rubber Jackets, and Calibration.  Analog Refractometer Replacement Daylite Plates/Covers.