(I'm posting to the list in case other conservators with hands on
experience in similar conditions want to check, disagree, agree and chime in)
 
Mary:
 
Interesting conservation problem, you have a lot of factors to consider
with compound-material artifacts like these. You may have to do some
testing to get some more information about the materials before you settle
on a treatment plan. The composition of the cupreous alloy in your brass,
the condition of the fibers in your paper, the adhesive that glues it to
the tin, and the pigment of the ink are all important factors which will
narrow your treatment options.
 
While you are figuring your plan out, its crucial that you have the tins
stored in very arid conditions-- bronze disease could still occur on your
brass at a relative humidity as low as 35 - 50%. Dessication within 48
hours of excavation is usually reccommended, and silica gel does this
pretty easily. Moisture will also adversely affect your paper (mold,
fungus, etc). This is assuming that the paper isn't wet and excessively
muddy to begin with... you'll have shrinkage problems if you dry it out too
fast in such a case. Also important is keeping them in dark storage,
oxidation is your enemy. Watch your Ph levels, too; always handle them with
gloves. This could be the way that these tins will have to exisit even
after treatment.
 
Cleaning of your brass is dependent on the compound itself, the level of
chlorides and the level of patinization (esp. presence of nantokite). If
you have chlorides, they have to go. Other than that, manually cleaning is
preferred... I have used baking soda with good results.  Inhibition with
BTA(benzotriazole) is standard for long term stabilization of cupreous
compounds, often it is enough of a treatment by itself. Go with very
careful spot treatment applications under a microscope. I don't know how
the BTA, or the solvent you use with it, is going to affect your
paper/glue/and ink.
 
Paper conservation is textile conservation with some twists, and textile
conservation is usually better left to experts. Solvent cleaning using
organic solvents or petroleum solvents (e.g white spirits) may prove to be
less destructive to your ink than D.I. water, which softens fibers.
Sterilization with a mild Lysol solution would stop mold and fungi.
 
It may be that all you have to do is lightly scrub the tins with some Arm
and Hammer, spot clean the labels, apply a few coats of BTA to the brass
and then seal it up. I'd go with an Acrylic sealant; I love Acryloid B-72,
commonly available as Krylon clear coat spray paint. Polyvinyl Acetate also
mixes with BTA.
 
These may help in addition to standard conservation texts:
 
Casey, P.J. and Cronyn, J.M.(eds) _Numistics and Conservation_, Occasional
Paper 1, Durham, U. of Durham, Dept of Archaeology.
 
Leene, J.E. (ed) 1972. _Textile Conservation_, Sevenoaks: Butterworths.
 
As a postscript, Wayne Smith at Texas A&M's Archaeological Preservation
Research Laboratory is doing almost miraculous things with compound
artifacts using various forms of silicone treatments. You may want to call
him.
 
Good luck,
 
David Johnson
 
At 08:36 PM 5/5/97 -0400, you wrote:
>Histarch readers:
>
>I am currently at the tail end of a 5-week data recovery project in a small
>Chinese American community in California.  We recently exposed a feature
>containing 20+ brass opium tins and lots of other opium associated materials.
> Six of the opium tins still have paper labels in excellent condition and I
>am concerned that they will begin to disintegrate.  Any suggestions on
>treatment, cleaning, preservation of these fragile items?
>
>Mary Maniery
>Sacramento, CA
>