Brightwell Refractometer Calibration 35 ppt — 35 ppt refractometer calibration solution - Brightwell

Brightwell Refractometer Calibration Standard 35 ppt — reference solution for marine refractometers

The Brightwell Refractometer Calibration Standard 35 ppt is a reference solution designed to accurately calibrate refractometers, hydrometers, and other density-measuring instruments used on marine aquariums. Formulated in the United States by Brightwell Aquatics, it matches the salinity of natural seawater exactly (35 ppt) — letting an aquarist verify and correct a reading before any critical measurement.

A drifted refractometer is one of the most common sources of error in marine aquarium keeping: a reading off by 2 to 3 ppt drives salinity adjustments that stress invertebrates and corals. Monthly calibration with this 35 ppt solution avoids that systemic pitfall.

What the 35 ppt solution is for and when to use it

• Monthly refractometer calibration — preventive routine to catch slow, invisible prism drift.
• After prism cleaning — systematic recalibration after any refractometer maintenance.
• New refractometer — first calibration out of the box to verify factory precision.
• Before a critical measurement — homemade salt prep, check after a big water change, quarantine setup.

Brightwell official calibration procedure

1. Shake the product well before use.
2. Clean the refractometer prism with fresh distilled water.
3. Dry the prism fully with a clean, soft, dry cloth.
4. Place several drops of Brightwell Refractometer Calibration Standard on the prism.
5. Wait 45 seconds, then calibrate to 35 ppt salinity.

Brightwell official specifications

• Specific gravity: 1.0264
• Refractive index: 1.3394
• Salinity: 35 ppt
• Conductivity: 53 µS/cm at 25 °C

Specifications

• Brand: Brightwell Aquatics (made in the USA)
• Format: 60 mL bottle
• Type: 35 ppt reference solution for refractometer and hydrometer calibration
• Compatibility: marine refractometers, digital hydrometers, density-measuring instruments
• Accuracy: matched to natural seawater parameters

Why choose Brightwell at ReefSolution

• Reef Casa ATC Refractometer — the reef refractometer to pair with this calibration solution for reliable readings.
• Aquaforest Reef Salt 22 kg — the reef salt to mix to 35 ppt after calibrating the refractometer.
• Coralife Deep Six Hydrometer — the reef backup hydrometer to cross-check the refractometer's reading.

Frequently asked questions

How often should I calibrate my refractometer?

Brightwell recommends monthly calibration as a minimum. On a refractometer used daily or recently cleaned, weekly calibration is even safer. The 35 ppt solution allows a fast check in a few minutes.

Can I calibrate a refractometer with tap water?

No — Brightwell does not spell this out but tap water carries dissolved salts that skew the zero calibration. Use only RO or distilled water to clean the prism, never tap water.

Why wait 45 seconds before reading the calibration?

Brightwell publishes this delay in the official procedure: the 45 seconds let the solution stabilize at ambient temperature and the prism reach thermal equilibrium. Reading too quickly gives a skewed result.

Can the 35 ppt solution be used on a hydrometer?

Yes — Brightwell notes the reference solution also fits hydrometer and other density-instrument calibration. The exact procedure differs by instrument — check the hydrometer manufacturer's documentation for use.