Re: [gardeners] pH
George Shirley (gardeners@globalgarden.com)
Fri, 21 May 1999 09:23:09 -0500
Kay Lancaster wrote:
> 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)
Knowing that Kay won't toot her own horn I'll take a chance on arousing her
ire and toot it for her. For those of you that are new to this list - Kay
Lancaster is a PhD Botanist and long-time gardener. In addition she taught
botany at the university level for a number of years. Might also add that she
is a really nice lady.
George