Refractometer Takes Out All the Guesswork

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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.

Darrell Nicholson, editor of Practical Sailor, grew up boating on Miami’s Biscayne Bay on everything from prams to Morgan ketches. Two years out of Emory University, after a brief stint as a sportswriter, he set out from Miami aboard a 60-year-old wooden William Atkin ketch named Tosca. For 10 years, he and writer-photographer Theresa Gibbons explored the Caribbean, crossed the Pacific, and cruised Southeast Asia aboard Tosca, working along the way as journalists and documenting their adventures for various travel and sailing publications, including Cruising World, Sail, Sailing, Cruising Helmsman, and Sailing World. Upon his return to land life, Darrell became the associate editor, then senior editor at Cruising World magazine, where he worked for five years. 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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