| Sampling
Bags
When collecting sand in the field you need some method of
keeping your samples safely separated until you get back to base. There
are a number of ways to achieve this but perhaps the most
cost effective and easiest way is using self-sealing
polythene bags, also variously called zip-lock, zip-seal or mini-grip
bags.
These are essentially polythene bags with a re-usable press-to-close zip along one edge,
making them ideal for
collecting sand samples in the field. They are available in a wide range
of sizes from about 38 x 63 mm up to 381 x 508 mm. My own
preference is for bags around 90 x 115 mm, a bit larger
than I need but easy to fill and seal. This size of bag
easily holds the 60 ml sample size I tend to collect. My own method is to use these sampling bags for temporary
storage, while collecting in the field and also for
archiving the spare sand samples after a small amount has been decanted into my final display
containers.
When collecting samples it is very important to label them
to prevent samples getting mixed up and this can be done
easily by using self-seal bags with write-on panels. These
bags come with a single white panel or set of three white panels on one side,
designed to allow you to write on them with a pen. A normal
biro does work but can easily be rubbed off and a permanent
marker pen is more foolproof.
When collecting sand at beaches, and other locations as
well, the samples can often be damp or even water-logged and
an easy way to prevent your collecting bag from getting wet
is to put the water-logged sample into a second bag, sealing
them both up carefully. Try not to get any sand particles in the seal
or it may leak and carry them upright as well.
When choosing a suitable size to serve as your sampling
bags it's not always best to go for the smallest bag that
will contain your sampled quantity. If you try and fill a
bag to maximum capacity it will place strain on the seal and
the contents are quite likely to spill when the seal fails.
Always go for a sampling bag larger than you need. As a guide I never
fill a bag more than half full.
Self-seal bags are quite cheap to purchase, costing only
a few pounds for batches of 100, the usual quantity sold. A
more cost effective option is to shop around and buy them by
the 1000. You also have less likelihood of running out of
bags when in the field. A 1000 bags can seem quite a lot but
it does not take long to use them up when a days collecting
can bring home as many as 50 samples.
An important tip when collecting in the field is to make
sure you have enough sampling bags with you. When I started
collecting I thought that 20 bags was enough but revised this
on a recent collecting trip when I gathered 44 different
samples. Now, as a rule I carry at least 100 sampling bags
with a full pack of 100 more in the car, just in case. You can also collect your samples in rigid containers
such as plastic bottles or even glass jars. However, these
are heavier and take up more space than cheap
polythene bags but are effective none-the-less. |
