Simon Fraser University Museum of Archaeology and Ethnology
The good archaeological detective very quickly learns to identify and
recover most of the finds from the area of the site he or she is digging.
But even the most sharp-eyed archaeologist is likely to miss a few things.
This is why it is useful to screen and float the
excavated soil to check for more things.
The simplest method of screening is carried out in a
hand sieve like the one shown below:
The screen can recover things that are missed due to temporary loss of
concentration or things that are too small to be noticed while digging like
beads, seeds and tiny bones.
When water is available on the site, like at DhRl 16, the process can
be improved.  There are several ways to do this:
One way is that the screen can be immersed slightly in water and gently
shaken. When you do this the soil dissolves and falls through, leaving behind
any objects.  The objects left behind are now easy to see among the remaining
rocks because they have been washed clean!
Another way to do the same thing is to gently shower water over the screen with
a hose.  This makes the soil fall through and washes the objects clean, same as above.
The most advanced way of doing this is called floatation.  Floatation is often used
to collect tiny seeds and plant remains from the soil.  Manual floatation is done
by using a set of screens that fit together: You put the soil on the top, gently spray
water over the top until all the soil dissolves and falls through, then pull apart your screens and voila! all the remaining seeds, plant remains and tiny bones are left behind!
Most floatation is done by hand like this but there is machines that do it for you.
In fact, at DhRl 16, there was a floatation machine near the site
that was used to collect plant remains.
Like all the other artifacts, anything found during screening is carefully recorded,
labeled and conserved until it can be studied in the laboratory.
Sometimes it is amazing what you discover in your screens.
You feel like a real detective, finding lost and hidden evidence!
Pretty neat, eh? If you think this sounds like fun, be sure to
check out the floatation activity page, you won't be disappointed!