Refractometer Takes Out All the Guesswork

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Refractometer Takes Out All the Guesswork

What matters most, our testing confirms, is not so much which brand of pink stuff you choose, but how you use it. Even the best product, mixed with too much water left in the line, results in a blend with unknown and perhaps unsatisfactory performance. While this may not be critical in North Carolina, sailors in Wisconsin need to get it right.

There is only one way to do that; measure the glycol as it comes out the other end of the plumbing. A $10 hydrometer from the local auto-parts store will do this. You have to collect a suitable volume in a cup, and if there is any oil (which floats) or dirt (which sinks), the reading will be affected. Remember to first check the calibration with water; if its off, buy a new one. In the end, you can guess based on color.

Or you can buy a tool that will last a lifetime, can be calibrated (small hidden screw on the bottom side) to read within 1 degree of the true freeze point of either PG or EG, using only a few drops, and will even read the state-of-charge on your batterys wet cells. We are speaking of the pocket refractometer, which looks like a small spotting scope.

In addition to changing the density of water, glycols, alcohols, and acid affect the way light is bent, and a refractometer can measure this change. To operate it, the user places a few drops of the target liquid on the prism, closes the cover, looks in the eye piece, and sees a sharp line that can be read in seconds

Pocket refractometers sell for $75 to $150 through many online auto-parts retailers.

Practical Sailor has been independently testing and reporting on marine products for serious sailors for more than 45 years. Supported entirely by subscribers, Practical Sailor accepts no advertising or any form of compensation from manufacturers whose products we test. Testing is carried out by a team of experts from a wide range of fields including marine electronics, marine safety, marine surveying, sailboat rigging, sailmaking, engineering, ocean sailing, sailboat racing, and sailboat construction and design. This diversity of expertise allows us to carry out in-depth, objective evaluation of virtually every product available to serious sailors. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser with more than three decades of experience as a marine writer, photographer, boat captain, and product tester. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.

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