Description
A dependable pH 4.0 reference for every calibration
Bluelab pH 4.0 Calibration Solution is the low reference point for a two-point pH calibration. Used after pH 7.0, it sets the slope of a pH pen, meter or controller probe so readings are accurate across the acidic range that nutrient solutions run in (Bluelab recommend pH 5.5–6.3 in solution). It works with every Bluelab pH product and any other meter that calibrates against a pH 4.0 buffer, and suits growers who calibrate several meters and controllers every month.
Key Benefits
- Genuine Bluelab pH 4.0 reference – the second point of a two-point calibration
- Pairs with pH 7.0 – calibrate at 7.0 first, then 4.0
- For every Bluelab pH product – pens, Combo Meter, OnePen, Guardian Monitor and controller probes
- Works with other brands that calibrate at pH 4.0
- Catches probe drift before it reaches a feed
Probe Drift You Cannot See
Every pH probe drifts as its glass ages and the reference junction is used up, and because the meter still shows a plausible number, the error goes unnoticed. Half a point out is enough to have you adding pH down to a reservoir that was already right, or leaving one where nutrients start to lock out and poor nutrient uptake follows. Bluelab recommend cleaning and calibrating pH probes every 30 days, and a calibration is only as good as the solution it uses: fresh, uncontaminated reference solution every time.
How to Use
- Clean the probe and rinse it in fresh tap water before calibrating.
- Pour a small amount of pH 7.0 and pH 4.0 into separate clean containers; never put the probe into the original container.
- Calibrate at pH 7.0 first, rinse, then calibrate at pH 4.0 (use pH 10.0 instead if you mostly measure above 7.0).
- Discard the used solution after calibrating; never pour it back.
- Store sealed, somewhere cool and out of direct sunlight.
- Recalibrate every 30 days, after every clean and whenever a reading looks wrong.
Technical Specifications
- Solution: pH 4.0 calibration buffer
- Use: second point of a two-point pH calibration, after pH 7.0
- Compatible with: all Bluelab pH pens, meters, monitors and controller probes; other pH meters that calibrate at pH 4.0
- Recommended interval: every 30 days and after cleaning (Bluelab)
- Storage: sealed, cool, out of direct sunlight
- Brand: Bluelab
Frequently Asked Questions
Do I also need pH 7.0 solution?
Yes. A two-point calibration starts at pH 7.0 and finishes at pH 4.0, so you need both.
Can I reuse the solution?
No. Pour out only what you need, calibrate, then throw it away. Returning used solution or dipping the probe into the container contaminates what is left.
Should I calibrate at pH 4.0 or pH 10.0?
Use pH 4.0 if you measure below pH 7, as with most nutrient solutions. Bluelab suggest pH 10.0 only if your readings are normally above 7.0.
Works Well With
