Bluelab pH 4.0 Calibration Solution – For Accurate pH Meter Calibration

What is Bluelab pH 4.0 Calibration Solution used for?

It’s used to calibrate pH meters at the acidic end of the scale, especially useful for hydroponic and coco growers where nutrient solutions typically run below pH 7. A two-point calibration with pH 7.0 and pH 4.0 ensures accurate readings.

Do I need to calibrate with both pH 7.0 and pH 4.0?

Yes. Most pH meters require a two-point calibration for best accuracy. Start with pH 7.0, then calibrate with pH 4.0 to cover the acidic range common in hydro and coco systems.

How often should I calibrate with Bluelab pH 4.0 Calibration Solution?

Monthly is a good baseline. If you're measuring daily or in warm, high-use environments, calibrate more often—especially if readings seem off or the probe is exposed to nutrient residue.

What sizes does Bluelab pH 4.0 Calibration Solution come in?

It’s available in single-use 18ml sachets and larger bottles like 250ml. Sachets offer fresh, uncontaminated solution every time, while bottles are more economical if you calibrate often.

Can I reuse Bluelab pH 4.0 Calibration Solution?

No. Reusing it, storing it in cups, or pouring it back into the bottle leads to contamination and inaccurate calibration. Always use a fresh amount and discard after each use.

What’s the correct way to use Bluelab pH 4.0 Calibration Solution?

Pour into a clean container, rinse the probe with clean water, then insert it into the solution. Avoid direct dipping into the bottle or sachet to keep the solution uncontaminated.

Do I need to clean the probe before calibrating?

Yes—if it has residue or salt buildup. At minimum, rinse it with clean water. A dirty probe can throw off calibration accuracy or cause the meter to fail calibration entirely.

What reading should I expect in pH 4.0 solution?

Your meter should stabilize close to 4.0. If it takes a long time to settle or won’t calibrate, check for a dirty, dry, or aging probe, or consider replacing the buffer solution.

Does temperature affect calibration with Bluelab pH 4.0?

Yes. For best accuracy, let both the probe and solution reach room temperature. Most meters have compensation features, but extreme temperature differences still impact results.

Is Bluelab pH 4.0 Calibration Solution compatible with all pH meters?

Yes. It’s a universal pH buffer and works with most pH pens and meters that support two-point calibration. It’s not suitable for EC or ORP meters, which require different solutions.

Can I store my pH probe in pH 4.0 Calibration Solution?

No. Use KCl storage solution for long-term probe storage. pH 4.0 is only for calibration purposes and won’t properly hydrate or preserve the probe.

What’s the difference between Bluelab pH 4.0 and KCl storage solution?

pH 4.0 is a buffer solution used during calibration to set meter accuracy. KCl storage solution is designed to keep the pH probe hydrated and functional between uses.

Is Bluelab pH 4.0 Calibration Solution safe to handle?

Yes. It’s low-risk with normal handling. Avoid eye contact, don’t ingest, and wash hands if spilled. It’s safe for hydroponics, indoor grows, and lab use when used correctly.

What’s the most common mistake with pH 4.0 Calibration Solution?

Reusing solution or contaminating it by dipping dirty probes directly into the bottle or sachet. Always use fresh solution in a clean container and rinse your probe beforehand.