Bluelab PH 7.0 calibration solution 500 ML

A 500 ml bottle of Bluelab pH 7.0 buffer, for anyone with several meters or many measuring points.

When the larger bottle actually costs you more

Per millilitre, 500 ml always beats 250 ml. That does not automatically make it the cheaper choice, and the reason is shelf life.

Buffer ages once air reaches it: carbon dioxide dissolves in and the value slowly shifts. That happens per elapsed month, not per millilitre used, a bottle standing half full on a shelf ages just as fast as one you use daily.

Which makes the arithmetic simple. Calibrate once a month using around 15 ml a time and 500 ml takes you nearly three years. By then the liquid at the bottom stopped being a reliable reference long ago, and you have thrown away most of your saving, or worse, you have been setting your meter against an expired value for years.

The rule of thumb: buy the bottle you will finish within about a year. For most growers with one meter, that is 250 ml.

This 500 ml is the right choice if you genuinely get through it:

• Several meters: a handheld, a monitor in the reservoir, perhaps a spare pen.
• Several rooms or sites, each with their own measuring routine.
• Continuously running monitors, whose probes wear faster and therefore want calibrating more often.
• A dosing computer, where a drifted probe translates directly into wrong dosing, so frequent calibration is not a luxury.

Technical Specifications:

• Value: pH 7.0
• Volume: 500 ml
• Brand: Bluelab
• Use: first calibration point (zero point) on any pH meter

Frequently asked questions

How long does an opened bottle stay good?
Work on about a year, provided you keep it open briefly and close it well. Write the opening date on the bottle.

Can I decant into a smaller bottle?
That does not help: decanting is itself an exposure to air. Better to keep the main bottle open only briefly.

Where should I store it?
Cool, dark and tightly closed: not in a warm grow room.