Date: Wed, 17 May 2000 09:41:42 +1000 From: Miguel de Salas <mm_de@postoffice.utas.edu.au> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1565$foo@default> Subject: Sand Types: which best?
At 02:29 PM 16-05-2000 -0700, you wrote:
>> You must use SILICA sand, because it is slightly acidic, it retains
>> moisture, and the mix with the Sphagnum more closely resembles the natural
>> habitat of CPs.
>
>The above is part of a recent message from "Strata, Inc."
><strata@flash.net> in a response to a question from Kit. Several times I
>have read in the CP digest the comment that silica sand retains
>moisture, suggesting that silica sand retains more moisture than other
>types of sand. Is the "retains moisture" statement intended to suggest
>that silica sand particle somehow absorbs moisture, in addition to
>retaining moisture by capillary tension on the sand surface and
>interstices? Moisture retention is related to the surface area of the
>sand particles, which is a function of grain size and shape. Silica sand
>is preferred by CP growers to other kinds of sand because it is inert
>and does not weather or decompose into "soil". Silica sand is used by
>sand blasters because of its hardness and resistance to abrasion. Pure
>silica sand (quartz sand) is what glass is made of. What am I missing?
>
A question for those out there, especially people involved with or dealing
with nurseries:
I have several types of sand available: coarse river sand, which is in fact
quite fine, but very dirty. After several rinses, the water still turns
brown/black from suspended clay particles. Sharp sand, which is quarried
from some local dunes. I am concerned that due to its proximity to the sea,
and its marine origin, and is spite of being quarried from pleistocene
deposits, it may be too rich in salts, esp. NaCl. Fat sand (trade term
here) which is a quarried sand as well, from the same location, but coarser
and rich in iron (yellow red, from a layer deeper in the horizon which has
had iron accumulation). Finally, washed river gravel. This one is very
clean, pure quartz fine gravel, but contains no sand. it ranges from about
half rice grain size to pea size, I consider it too coarse.
There is one other. I can buy double washed river sand as "propagating
sand", but the cost is huge: AUS $5 for 5 liters. All the others are on the
range of $2-3 for 25l, or by the cubic meter.
Any thoughts on the matter? the sharp sand is clean and white, but being
from coastal dune deposits, I am concerned about the salt. Should I just
wash them myself?
Miguel de Salas
School of Plant Science,
University of Tasmania,
PO Box 252-55, Sandy Bay, Hobart
Tasmania, Australia, 7001.
mailto://mm_de@postoffice.utas.edu.au
My Moths Page:
http://members.xoom.com/migueldes/moths/moths.html
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