Refractometer Calibration Standard - 60 ml

Brightwell Aquatics Refractometer Calibration Standard is a precision reference solution for calibrating seawater refractometers and checking other salinity- or density-measuring instruments.

The solution provides a 35 ppt salinity reference, corresponding to a specific gravity of 1.0264 and refractive index of 1.3394. Calibrating at 35 ppt places the reference point near the salinity commonly measured in reef aquariums, helping users obtain dependable readings within the instrument’s normal working range.

Accurate salinity measurements are essential when mixing saltwater, performing water changes, acclimating livestock, and maintaining a stable marine aquarium. A refractometer that is out of calibration can lead to unnecessary salinity adjustments even when the aquarium water is already within the intended range.

Shake the solution before use, clean and completely dry the refractometer prism, apply several drops, wait 45 seconds, and adjust the instrument to 35 ppt.

• Provides a 35 ppt seawater calibration reference
• Corresponds to 1.0264 specific gravity
• Corresponds to a refractive index of 1.3394
• Helps identify and correct inaccurate refractometer readings
• Calibrates near the salinity range commonly measured in reef aquariums
• Supports more consistent saltwater mixing and aquarium maintenance
• Simple calibration procedure takes approximately one minute
• Suitable for checking seawater refractometers and compatible density-measuring instruments
• Formulated with high-purity salts
• Convenient 60 mL size for routine refractometer calibration

Refractometer Calibration

1. Shake the bottle thoroughly before use.

2. Rinse the refractometer prism with fresh distilled water.

3. Dry the prism completely using a clean, soft, lint-free cloth. Confirm that no water, salt, or visible residue remains.

4. Place several drops of Brightwell Aquatics Refractometer Calibration Standard on the prism.

5. Close the refractometer cover plate so the solution spreads evenly across the prism without trapped air bubbles.

6. Wait 45 seconds to allow the sample and instrument to stabilize.

7. Look through the refractometer and follow the instrument manufacturer’s calibration procedure.

8. Adjust the calibration control until the boundary line reads 35 ppt salinity.

9. Remove the calibration solution and rinse the prism with fresh distilled water.

10. Dry the instrument completely before testing aquarium water or returning it to storage.

Always follow the refractometer manufacturer’s instructions when they specify additional calibration or temperature-compensation requirements.

High-purity salts in a prepared aqueous calibration solution.

Brand: Brightwell Aquatics
Product: Refractometer Calibration Standard
SKU: RES60
Product Type: Seawater salinity calibration solution
Volume: 60 mL (2 fl oz)
Reference Salinity: 35 ppt
Reference Specific Gravity: 1.0264
Reference Refractive Index: 1.3394
Reference Temperature: 25°C (77°F)
Primary Application: Seawater refractometer calibration
Composition: High-purity salt solution
Country of Manufacture: USA

• One 60 mL bottle of Brightwell Aquatics Refractometer Calibration Standard

• Keep the bottle tightly closed when not in use.
• Prevent aquarium water, distilled rinse water, salt residue, or other contaminants from entering the bottle.
• Do not return used calibration solution to the original container.
• Use clean dispensing and testing equipment.
• Keep the solution away from excessive heat and direct sunlight.
• Do not use the solution if contamination or evaporation is suspected.
• This product is intended for calibrating aquarium salinity-measuring equipment.
• Do not add the solution to an aquarium.
• Not for human consumption.
• Keep out of reach of children.

The Refractometer Will Not Calibrate to 35 ppt

Confirm that the instrument has an adjustable calibration control and that the correct control is being used. Clean and dry the prism, apply fresh solution, wait 45 seconds, and repeat the calibration according to the refractometer manufacturer’s instructions.

The Reading Changes Between Tests

Make sure the bottle is shaken before use, the prism is clean and completely dry, and enough solution is applied to cover it evenly. Allow the full 45-second stabilization period before reading.

The Boundary Line Is Blurry

Clean the prism and cover plate, apply enough solution to cover the prism, and close the plate carefully. Check for trapped air bubbles, uneven coverage, or insufficient lighting.

The Reading Is Lower Than 35 ppt

The prism may still contain distilled water from cleaning, which can dilute the calibration sample. Dry the prism completely and repeat the test with fresh solution.

The Reading Is Higher Than 35 ppt

Salt residue may remain on the prism, or evaporation may have concentrated the sample. Rinse with distilled water, dry completely, and recalibrate with fresh solution directly from the bottle.

Calibration Changes With Room Conditions

Allow the refractometer and solution to reach the same stable room temperature before calibration. Avoid calibrating immediately after either item has been stored in an unusually hot or cold location.

The Solution May Be Contaminated

Do not pour used solution back into the bottle. If contamination or substantial evaporation is suspected, replace the solution rather than relying on an uncertain reference.

Q: What value should I use when calibrating my refractometer?
A: Adjust the refractometer until it reads 35 ppt salinity.

Q: What specific gravity corresponds to this solution?
A: The manufacturer specifies a reference specific gravity of 1.0264.

Q: What is the reference refractive index?
A: The specified refractive index is 1.3394.

Q: Why use a 35 ppt solution instead of distilled water?
A: A 35 ppt standard calibrates the instrument near the salinity range normally measured in marine and reef aquariums.

Q: How long should the solution remain on the prism?
A: Wait 45 seconds before adjusting or reading the refractometer.

Q: Should I shake the calibration solution?
A: Yes. Brightwell instructs users to shake the bottle before calibration.

Q: How should I clean the refractometer before calibration?
A: Rinse the prism with fresh distilled water and dry it completely using a clean, soft cloth.

Q: Can I reuse the solution from the refractometer?
A: No. Discard the used sample to prevent contamination of the original bottle.

Q: Can this solution be added to my aquarium?
A: No. It is a calibration reference for salinity-measuring equipment, not an aquarium additive.

Q: How often should I calibrate my refractometer?
A: Follow the instrument manufacturer’s recommendation and recalibrate whenever readings appear inconsistent, after the instrument has been dropped or stored for an extended period, or before making important salinity adjustments.

Q: Can it be used with a digital refractometer?
A: It may be used when the instrument supports calibration with a 35 ppt seawater standard. Follow the digital refractometer manufacturer’s specific instructions.

Q: What should I do if my refractometer still gives inconsistent readings?
A: Clean and dry the prism, use fresh calibration fluid, allow the solution and instrument to stabilize at the same temperature, and repeat the calibration. If readings remain unstable, inspect or service the instrument.