Product Review: Duplex II and Rayner Dialdex Refractometers


For decades, I used a Gem Instruments Duplex II refractometer exclusively. Many regard it as the best refractometer available in the United States. In Europe, on the other hand, the Rayner Dialdex refractometer is considered the best. Shipping costs have kept these from being regularly traded across the Atlantic. As a result, most people don’t have a choice of brands. However, you can safely say both are top-quality manufacturers.

While reviewing “no name” refractometers, I read that the Duplex II is the only refractometer designed specifically for spot readings. As I discovered, the “no name” brand units were almost useless at spot readings. I was left wondering how much their smaller size had to do with that.

As an experiment, I purchased a Rayner Dialdex. It’s considerably smaller than the Duplex II and about the same size as a “no name” brand. Both of these instruments are expensive. New, the Duplex sells for around $625. (Editor’s note: You can find used Duplex II and Dialdex refractometers for sale online at lower prices).

How do they compare?

Ease of Use

At first, I found the Rayner Dialdex very awkward to use. However, I soon got comfortable with it. …

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Content Length 821 words
Reading time 4 min 6 sec

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  • Ease of Use
    • Polarizing Filter
    • Finding the Shadow Line
  • Clarity of Readings
    • Refractive Index Readings
    • Spot Readings
  • Conclusion

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