March 1999 - Society for California Archaeology

16
New Methods and Technologies
Additional experiments showed that the rate of clay
distintegration seemed to be directly proportional to
the density of the sodium bicarbonate solution (Van
Horn and Murray 1982:25).
However, they do not furnish numbers. My second experiment
was designed to assess this relationship. I used the same
test apparatus described above. This time I thoroughly mixed
a large quantity of clay so as to assure uniformity, and then
divided this into 300 g samples, which were then formed into
bricks. Again I used plain water as a control. The test solutions
contained 10.0, 20.0, 30.0 , 40.0, 50.0, 60.0, 70.0, 80.0,
and 90.0 gm per liter of water. The water temperature was
62 o . I was not able to get all 90 gm of baking soda dissolved,
and this was also true for the 80 gm of baking soda, but less of
a problem than with the highest amount. I allowed the
experiment to run for 4.5 hours, using only gentle lifting and
tilting to pour off clay particles once per hour. While the
control brick was virtually unchanged by this process, the
baking soda again caused the bricks to soften and fall apart. I
collected, dried, and weighed the clay particles in the trays
and whatever portions of the bricks remained behind in the
baskets. The findings are depicted in igure 4. The point of
diminishing returns is evident at around 70 gm.
These findings suggest at least two, alternative processing
methods. Assuming an interest in recycling the baking soda
solution, I would suggest starting with 30.0 or 40.0 gm per
liter and periodically adding fresh solution as needed.
Alternatively, with no recycling, a maximum concentration
would be about 70.0 gm per liter.
Dry weight (gm) disintegrated clay.
225.00
200.00
175.00
150.00
125.00
100.00
75.00
50.00
25.00
0.00
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0
Sodium bicarbonate (gm) per liter of water.
Figure 4: Results after 4.5 hours soaking in graded solutions of
sodium bicarbonate.
Van Horn, David A. and John R. Murray
1982 A Method for Effectively Screening Some Clay
Matrices. In Practical Archaeology: ield and Laboratory
Techniques and Archaeological Logistics, Brian Dillon,
ed. Institute of Archaeology, University of California, Los
Angeles, Archaeological Research Tools, Volume 2: 23-31.
Proposed Schedule for Newsletter
Regional Reports
Regional reports will follow the “News from the ield”
format found in Newsletters past. Contributing regional
editors will offer one report every two years on a set
schedule. The reports will be a digest of the most significant
archaeological/cultural heritage activities in each
region in the last two years, following a project-by-project or
thematic (e.g., “Early Holocene archaeology”) organizing
principle. The masthead illustration on the facing page will
highlight the pertinant region in turn.
The regional editors are intimately familiar with their
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arms. Help them out by supplying them with information
about your activities! Two regional editor positions are still
open. If you are interested, please contact the Editor,
gwhite@csuchico.edu.
by issue
by region
Vol. # Contributions Region
33 1 Underwater
33 2 Northwest W Mojave/SJo
33 3 Northcentral Mojave/Colorado
33 4 Northeast E Sierra
34 1 C/N Sierra San Diego Co.
34 2 S Sierra Orange/LA Cos.
34 3 Bay Area ??
34 4 Central Coast ??
Region Vol. # Submit When? Editor
Northwest 33 2 14 May, 1999 Tom Keeter
Northcentral 33 3 13 August, 1999 Eric Ritter
Northeast 33 4 12 November, 1999 Gerry Gates
C/N Sierra 34 1 11 ebruary, 2000 Susan Lindstrom
S Sierra 34 2 12 May, 2000 Kristina Roper
Bay Area 34 3 11 August, 2000 Mark Hylkema
Central Coast 34 4 11 August, 2000 open
E Sierra 33 4 12 November, 1999 Don Laylander
Mojave/Colorado 33 3 13 August, 1999 Mark Basgall
W Mojave/SJo 33 2 14 May, 1999 Mark Campbell
Orange/LA Cos. 34 2 12 May, 2000 open
San Diego Co. 34 1 11 ebruary, 2000 Bryan Byrd
Underwater 33 1 12 ebruary, 1999 Jack Hunter