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SomervillesBrew
10-21-2009, 12:58 PM
Should a salinity refractometer with a specific gravity scale be OK for testing gravity of wort?
I figured that the specific gravity of a liquid would be the same whether it was a saline solution or sugar.
However, I used a salinity refractometer for testing my wort and it said that it was over 1.070, I then used two different hydrometers to double and triple check, but found 1.050 on both hydrometers.
I calibrated all three instruments with distilled water.

Should a salinity refractometer with a specific gravity scale be OK for testing gravity of wort?

Scott M
10-21-2009, 01:22 PM
Why would you?

The instrument isn't the issue. All refractometers will give you a visual of the "gravity" or density of the liquid.

They are about $45 - $80, it isn't worth the lost product because you don't have the right equipment, or can't trust what you're reading.

What was the temperature of the wort? Did you convert for temp when measuring with the hydrometers?

JTremblay
12-10-2009, 01:36 PM
Sorry for the late reply, but I know about these for my aquariums.

The long and short of it is that most aquarium refractometers are not accurate across their entire range -- i.e., if you calibrate them with RO water (1.000), they are unlikely to be accurate at 1.026 (salinity for a marine tank). And, sometimes, the measurements can be off by more than 10% from the low end to the high end.

You can, of course, compensate for the difference ...

But only after playing around with either a hydrometer or samples of a known gravity.

Mad-Brewer
12-11-2009, 05:16 PM
"Should a salinity refractometer with a specific gravity scale be OK for testing gravity of wort? I figured that the specific gravity of a liquid would be the same whether it was a saline solution or sugar."

The issue I think is the 'refractive index' of both sugar and salt. Each bends light differently. Salt has an index value of about 1.5 but sugar at 30% concentration is about 1.38. The refractometer is calibrated for an index relevant to sugar.