Expert: Ralph Salier - 12/13/2006

Question
Hello again Dr. Salier,
thanks for taking the time to look into this for me.  Much of this information is locked away in the halls of academe, and finding it from theoutside can be difficult.  

I was trying to be concise so as to not bore you, or take too much of your time.  But, you have asked ... look out, I love my work.

I acquired both pieces in question last year in Asia, where they were in a personal collection, and in the same climate from which they originated.  The panels, to clarify, no longer have lichen growth ... just the marks, including an imprint or two that are merely a grain of sand in depth.  My reason for asking about the pitting is to double confirm the origin of the pitting and impritns.  they are Viet Khmer, which is little documented outside of mostly lost french books.  Stylistically, they meld both Bayon and Angkor Wat styles ... and I had one 'expert' state that they were probably 13th  century.  This, I highly doubt .. condition is too good, and the fact that the styles of the two period meld indicates that they were later, what I call the "glory days" influence.  I have an earlier piece or two that are Viet Khmer, and they both evince strong Lopburi type influences.  so, outside of the minor exfoliation typical of anything of that age that has had exposure to erosive elements, they are in fine condition.  Its just a matter of confirming authentication I've done.
Oh .. there is one thing, a matter of curiosity .. the presence of a white substance, predominantly around the higher relief work that has fractured along the sedimentary lines.  I sent samples of it and of the lion to a botanist at my alma mater, but she could see no signs of biological growth or cellular structure.  I thought it was a bad paste job, but as it is not restricted purely to the fractures, it occurred to me that they might be either a growth that caused the fractures, or one that grew from the paste used (as in your mentioning of the hazards of Elmers.).  Sorry, an aside .. speaking of Elmers, the current formula contains elements not overly desirable.  It was changed about 15 years agao .. but I know what you mean.

The samples I sent of the lion: there is a very minute 'furry' texture to elements of it, so I was unsure as to the nature of the growth.  While otherwise the symptomology was that of autotrophic bactieria, I figured it best to make sure.  While the microscope used was not quite powerful enough to view individual bacteria, it was able to confirm my own observations of a very thin 'slime coat' (I viewd this at around 120x), as well as spotting consistent with bacterial colonization.

When it arrived, neither the coloration nor the degree of exfoliation were evident.  It was not until about 4-5 months later that I noticed it, and started the research.  The first source I found reccomended the prompt mechanical removal of the worst spots.  Rather than that, I figured using a hose to remove it would be far less detrimental, particularly as I could bake it in the sun afterwords.  In the months that have followed, outside of study, no treatment has been done, and the problem has not increased.  My thought is that: the presence of the bacteria, while in situ and over time, would have eaten much more of it away.  However, at the time I had it, it had penetrated to about 1mm or so, and the presence of the inter bacterial bonds, the "slime coat" was actually holding that layer together.  When climate change caused it to falter or die off, the exfoliation occured. Oh .. I'm in the Seattle area, and it arrived in winter.  So, the combination of cooler temperatures and less humidity of the interior environment here is what I am thinking of. (bronzes on the other hand .. summer, with the similar humidity but higher salt concentration in the air .. ugh.  everything has to be maintained on a weekly basis).

the current situation is stable, but more fragile than I would like.  In spite of my mercantile status, I care about these things.  Document them, study them, create grand theories and the works.  If and when they find a new home, they should be stable and protected.  I won't sell them if not, unless to someone who knows as much as I or more, and cares as much or more.  Pictures are available, including some microscopic shots of up to around 12ox.  Because I'm a fan, and think that they might be useful to you.. the lenses I use to get that are Raynox, around $125, and snap onto the end of a 135mm or greater lens of 35mm type.  I use a Fuji digital "slr style" camera, with a 10x zoom and 5 mp, which according to the few shots I have taken with a mm guide I made, works out to about 120x at its max.  Thats with the 36x magnifier .... kit comes with 6x and 12x as well.

Panels are in relief, a complete set with integral bordering, and measure a total of 43"x31"h.  the Lion is Cham, probably thap mam period, and (one of the indicators of this) in the round.  Showing the later influence similar to Balinese art, it is highly detailed, with the bottom third being a base with a Kala face to the front.  It measures about 35" in height.

As to your thoughts .. given the desirability of possible removal, would a really dilute solution of Acryloid B72 in ethanol be maybe the best? I know its used on bone as well, but I believe with an acetone base .. not sure of the desirability of that solvent on stone. Around 2-3%?  Pretreatment would definitely not be bleach.  More likely the use of strptomycin or similar broad spectrum topical antibiotic (streptomycin is recommended in the lit.), or possibly a vinegar bath followed by steam.  the streptomycin is easy to find in the midwest as it is a treatment ofr fireblight, a fruit tree problem, but not around here.  My vet recommended a couple of alternatives, but I have not researched them yet.  Oh, should you need the idea, it is soluble in ethanol, which allows for pretty good penetration of the surface.

Spending is limited ... I've been at this a few years, but I am not running a profit, and live at minimum myself.  New location combined with my more academic approach probably havent helped.  To be honest (not a sales pitch)when I first got into this 4 years ago, the idea was to sell such items to museums and such.  Unfortuantely, such door s are hard to get through.  Must be my lack of grey hair.  So, everything is out of pocket.  Its one of the reasons I have spent the last year studying conservation methods and material for a variety of subjects.  That, and i find it fun and rewarding.
Wild ideas ... I thrive on them.  Shoot, if you work with metals, could probably give you a few wild ideas that work great.  But, sandstone coins are hard to come by as experimental material, and I have a few friends who are experts in archaic and later weaponry .. which helps.

Probably far more than you wanted to know, but hope it helps.
Best,
Nathan


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The text above is a follow-up to ...

-----Question-----
hi Mr./Dr. Salier,
I've been banging my head against this wall for a while, so I am hoping you can help wither directly or by pointing me in the direction of where to find the appropriate information.
this actually concerns 2 pieces, both Vietnamese.  The first is a sandstone lion figure, circa 13th/14th century. Courtesy of an autotrophic bacterial infection, it has an exfoliation problem.  While the infection is relatively easy to remedy, I don't wish to do it until I can get something to safely consolidate the surface, in spots at the very least.  Conservare is out of the question, as it is apparently only available in 4 gallon buckets at a price well beyond what i can spend.  Will a microcrystalline wax treatment in particularly rough spots 'smother' the sandstone?  Or is there something else I canuse?  Maybe acryloid, if just in spot treatment?

On the other, a 16th c. or earlier Viet Khmer set of sandstone panels, I just wanted to ask if you were aware of anywhere I could find pictures of pitting left behind by lichen hyphae/thallus.  part of my authentication, i have found diagrams, but direct photographic comparison would be very hlepful.
thanks for whatever help you can give,
nathan
-----Answer-----
Hi Nathan,  I appologise for not responding sooner.  This required/requires additional research.  Exfoliation on sandstone is not uncommon and there are numerous causes as well as solutions to the problem.  However, you are looking for inexpensive solutions, these are hard to come by, thus the research.  How much can you spend and are you open to "wild ideas or concepts"?

The pitting caused by the Lichen are more problamatical.  It greatly depends on a number of factors not the least of which is the nature of the environment they were "living in" prior to their "rescue" and what was used to remove them.  Sometimes the removal of a lichen can be more destructive then just allowing it to exist or the "cut it back".  

For these panels, you should contact the conservation department of the British Museum in London as they have the most experiance with this kind of material and damage.  They may be able to provide some guidance for both curation/preservation and authentication.  Ask for the curator of South East Asian Artifacts and materials.  They will ask questions, I hope you are prepared to answer them.

Going back to the lions.  There are some polymer solutions you can use that will also do justice to the bugs.  Many are a urathane based solution where you thin the urathane but not to the point where it will no longer bond but can penatrate the stone and as it hardens through the evaporation of the solvant consolidates the surface and makes it rather hard.  This is similar to what can be used on friable bone to harden it for study.    There are also some types of glue like Elmers which, when thinned down with water will work as well but the bugs like Elmers so you would need to kill the bugs first.  If you plan to use bleach, be VERY CAREFUL as you may cause more harm then good depending on the nature of what is holding the sandstone together in the first place.  

The wax can work but it will cause problems later when trying to do other conservation work or when cleaning the stone.  You could also experiment with lacquers, tong oil and preservatives used on wood, especially those which are thin enough or can be thinned to move more freely into the substrate.  BUT These should be tested first in very small areas in obsucure locations so as to damaging the visual surfaces.  

If you could tell me the situation you are in relative to the conservation of these items, I may be able to suggest funding resources for the curation of the objects.  Where are they located?  Does it involve only these items or are there others?  I am hoping that you are willing to provide me answers to these questions.

Answer
Hi Nathan,  That is a lot to absorb.  The layering that you are seeing may be the mineral salts which are naturally occuring in the matrix of the sand stone.  This can cause exfoliation under the right circumstances espcially if the surface was in anyway sealed in the past.  The stone needs to breath and since most sand stones are "wet" there is a constant migration of minerals in the stone.  

I have pulled together some websites and two people you can use as contacts who may be willing to help you out.  I've not spoken to them but would be willing to do so if you request it of me.  

As follows:

www.springerlink.com/content/t529w74125562795

www.everlifememorials.com/headstone/cleaning-cemetary-tombstones.htm (learning center)

www.gravestonepreservation.info/grart-10.asp
www.  "     "     "     "   "  /gravestone-articles.asp

Matthew C. Reiley
Conservation Manager, Central Park NYC
347-236-9461
mreiley@centralparknyc.org

M.Reiley
Conservation Manager,CPC
79th St. Maint. Yard
Central Park, NY, NY 10024


Pat Plunkett - Stone Restoration expert
34 Hickory Ave
Takoma Park, MD 20912
301-270-9475

Patplunkett@comcast.com


Try these resources and if this is not enough, come on back and I'll see what else I can find.  You may want to take the tac that you are working with grave stones so as to avoid any kind of questions as to the origin of the artifacts from Asia.  This especially true for Pat.

Some of these sources also speak about some books as resources for you as well.

Please keep me informed and again if you would like me to contact these two individuals and act as go between I would be willing to do so.

By the by, my email is rsalier@hotmail.com