Re: [gardeners] pH
Kay Lancaster (gardeners@globalgarden.com)
Thu, 20 May 1999 21:14:04 -0700 (PDT)
Both of these sites are offering pH meters of considerably better quality
than the $20 ones commonly sold in gardening stores that look like a old
fuel gauge with a couple of stout wires sticking out of the bottom. That
variety gives wierd and wonderful (but rarely accurate) measurements, and
you can often watch the needle drift around in a buffer solution of known
pH. Nor can you get several to agree with one another. A few years ago,
I put three of them in a beaker with pH 7.01 buffer used for calibrating
lab meters, and got simultaneous readings of 5.5, 7.4 and 8.3.
In contrast, a paper like pHydrion is about 1/4 the price and has an
accuracy of about 0.5 pH units... more than close enough for all but the
most finicky plants.
In my opinion, after doing many critical pH measurements over the years,
I can't find a pH meter that costs less than about $50 I'd be willing to
trust as a substitute for pHydrion at $5.00.
And there are more accurate indicator strips available through
various scientific supply companies... they simply provide more
precision than you need for garden pH measurements, and at a higher
cost. If you do require more precision (for hydroponics, for instance),
there are short range pH papers that will give you a good 0.2 unit
precision within that range, and they're a whole lot easier to use
than calibrating a meter and keeping the electrodes properly cleaned
and fed, in my opinion.
Kay Lancaster kay@fern.com
just west of Portland, OR USDA zone 8 (polarfleece)