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Re: [ANE-2] Re: Help with baking a tablet

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  • Robert M Whiting
    In addition the BM s instructions (which are, of course, excellent) I have a few addtional words of advice. The preheating of the tablet(s) is very important.
    Message 1 of 6 , Jul 7 12:05 AM
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      In addition the BM's instructions (which are, of course, excellent) I have
      a few addtional words of advice.

      The preheating of the tablet(s) is very important. Its purpose is to get
      rid of any moisture that may be inside the tablet. If the tablet is not
      thoroughly dried before firing, moisture inside the tablet may be
      converted to superheated steam and cause the tablet to explode.

      Do not be surprised if your tablet comes apart into several pieces during
      firing. They can be rejoined using an adhesive suitable for pottery as
      described in the BM instructions. At the OI, we always used Duco cement
      diluted with acetone.

      Do not count on the firing to remove the salts in the tablet. After
      firing, the tablet should be soaked to remove the salts. Once fired the
      tablet can be safely immersed in water. Use distilled water and change
      the water every day or two. Continue until there is no trace of salt in
      the water. If you do not remove the salts from the tablet, they will
      recrystalize and eventually destroy the tablet.

      Bob Whiting
      whiting@...


      On Sat, 6 Jul 2013, imbros03 wrote:

      > Hi Larry,
      >
      > A friend of mine send me the protocole followed by the BM. I copied it and pasted below.
      >
      > I have sent a message to your e-address that is in the ANE-2 group asking for some technical information about your tablets that probably is not of interest of the rest of the group,
      >
      > Best regards
      >
      > Aldo Tamburrino, Ph.D.
      > Dept. Civil Engineering
      > University of Chile
      > ____________________
      >
      > Standard Baking for most Cuneiform Tablets
      >
      > The modified schedule that we[BM] have adopted is as follows:
      >
      > Room temperature to 140C at 19C/hr, hold 24 hrs
      > 140 to 630C at 50C/hr, hold 4 hrs
      > cool at 29C/hr to room temperature
      >
      > A small proportion of tablets from almost all of the 22 sites in our
      > collections can react adversely to the firings. The archaic tablets
      > from Nineveh are thought to be particularly stable and infact very few
      > of them have ever required treatment.
      >
      > Special Instructions for Very Large Cuneiform Tablets
      >
      > One of the things we were particularly interested in was if tablets from
      > different sites or periods required different firing schedules. This
      > could be caused if different clay sources were used. The thermal
      > analysis that we commissioned, showed that the tablets fell into three
      > groups, one of which included tablets from northern sites, the other
      > southern sites and third that had already undergone some form of
      > heating. With only minor differences between them, the schedule was
      > designed to encompass all three of the groups we identified. The only
      > real evidences of a different clay source came from two analyses of
      > tablets from Kanesh in Anatolia. All of this does not mean that there
      > aren't groups of tablets that different thermal behaviour, but just that
      > we did not identify any within our collection, which originates mainly
      > from Mesopotamia, but covers most periods.
      >
      > The drying required for larger (thicker) tablets, especially freshly
      > excavated material that could contain significant water [is longer].
      > This can be accommodated by extending the hold period at 140C to maybe 3
      > days. For thick tablets it is also prudent to extend the hold period at
      > 630C, maybe to 24 hours.
      >
      > A higher temperature firing would give higher strength and some of the
      > salts would be removed by glass formation in the fired tablet. However
      > there is considerable risk from calcite degradation between 660 and 720C
      > and the firing schedule would need to be carefully designed to minimise
      > this risk. We have evidence that this is the cause of a large portion
      > of the damage we observe during tablet firing. Also our curators feel
      > that surface texture is an important feature of the tablets (as it aids
      > in making joins) and that over firing alters this. The small number of
      > tablets intentionally firing in antiquity were fired to these higher
      > temperature and another reason for keeping to lower temperatures is that
      > this allows easy discrimination of these intentionally fired tablets
      > from those that have been fired for conservation purposes.
      >
      > Consolidation and Gluing of Cuneiform Tablets
      >
      > Fired tablets are reconstructed with HMG cellulose nitrate adhesive
      > which has been successfully used for more than 30years in the
      > department. It is sometimes necessary to locally consoldiate loose
      > areas, or flakes of tablets or break edges, it is not normally necessary
      > to consolidate the whole surface of a tablet.
      >
      > Tablets which require consolidation are treated in varying
      > concentrations of Paraloid B72 in 50/50 acetone and industrial
      > methylated spirits usually 2 to 10%. The material will only dissolve in
      > acetone the IMS is added to reduced evaportion. The consolidant is
      > pipetted onto the surface and allowed to dry before reapplication. There
      > is a great risk of darkening of the tablet which can be very much
      > reduced by using less volitile solvents or reducing the evaportion of
      > the solvent by placing the tablet in a chamber, overing with glass or
      > wrapping in clingfilm [catering thin plastic film]. B72 has a low glass
      > transition temperature which means the resin will soften around 40c
      > which may be a problem for you, Paraloid B67 has a tg of 50c.
      >
      >
      > --- In ANE-2@yahoogroups.com, "larryjhs01" <larryjhs@...> wrote:
      > >
      > > Hello
      > >
      > > I have an UrII tablet in my vast collection, but it is rather fragile
      > > and the clay is beginning to crumble. There is also a bit of salt on
      > > the surface.
      > >
      > > Can anyone in the world of 'cuneiform care' provide me with baking and
      > > other instructions (I can get access to a pottery kiln).
      > >
      > > Thanks.
      > >
      > > Larry Stillman
      > > Monash University
      > >
      >
      >
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
    • Adapa@...
      Dear Bob, I believe that the British Museum no longer soaks tablets due to the occasional formation of a disfiguring white bloom which sometimes results. The
      Message 2 of 6 , Jul 7 6:45 AM
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        Dear Bob,

        I believe that the British Museum no longer soaks tablets due to the
        occasional formation of a disfiguring white bloom which sometimes results. The
        reasons for this are complex, and not just related to the use of hard water,
        as some have suggested. I understand that they have checked that the
        stability of the temperature and humidity of their storage conditions means
        recrystallization is unlikely to occur.

        In my opinion, soaking is still very much worth while, although it is only
        effective for surface salts. Capillarity seems to prevent the tablet core
        from effectively being washed, and even after months of fresh water changes,
        core samples can still show high levels of soluble salts. The bloom can be
        prevented by the addition of a calcium sequestering agent - such as
        "Calgon" - to the soaking water, which is practical for small scale conservation,
        but not on the industrial scale they need at the BM.

        Regards,
        Mark

        (Mark Wilson)



        In a message dated 07/07/2013 09:05:38 W. Europe Daylight Time,
        whiting@... writes:




        In addition the BM's instructions (which are, of course, excellent) I have
        a few addtional words of advice.

        The preheating of the tablet(s) is very important. Its purpose is to get
        rid of any moisture that may be inside the tablet. If the tablet is not
        thoroughly dried before firing, moisture inside the tablet may be
        converted to superheated steam and cause the tablet to explode.

        Do not be surprised if your tablet comes apart into several pieces during
        firing. They can be rejoined using an adhesive suitable for pottery as
        described in the BM instructions. At the OI, we always used Duco cement
        diluted with acetone.

        Do not count on the firing to remove the salts in the tablet. After
        firing, the tablet should be soaked to remove the salts. Once fired the
        tablet can be safely immersed in water. Use distilled water and change
        the water every day or two. Continue until there is no trace of salt in
        the water. If you do not remove the salts from the tablet, they will
        recrystalize and eventually destroy the tablet.

        Bob Whiting
        _whiting@..._ (mailto:whiting@...)

        On Sat, 6 Jul 2013, imbros03 wrote:

        > Hi Larry,
        >
        > A friend of mine send me the protocole followed by the BM. I copied it
        and pasted below.
        >
        > I have sent a message to your e-address that is in the ANE-2 group
        asking for some technical information about your tablets that probably is not of
        interest of the rest of the group,
        >
        > Best regards
        >
        > Aldo Tamburrino, Ph.D.
        > Dept. Civil Engineering
        > University of Chile
        > ____________________
        >
        > Standard Baking for most Cuneiform Tablets
        >
        > The modified schedule that we[BM] have adopted is as follows:
        >
        > Room temperature to 140C at 19C/hr, hold 24 hrs
        > 140 to 630C at 50C/hr, hold 4 hrs
        > cool at 29C/hr to room temperature
        >
        > A small proportion of tablets from almost all of the 22 sites in our
        > collections can react adversely to the firings. The archaic tablets
        > from Nineveh are thought to be particularly stable and infact very few
        > of them have ever required treatment.
        >
        > Special Instructions for Very Large Cuneiform Tablets
        >
        > One of the things we were particularly interested in was if tablets from
        > different sites or periods required different firing schedules. This
        > could be caused if different clay sources were used. The thermal
        > analysis that we commissioned, showed that the tablets fell into three
        > groups, one of which included tablets from northern sites, the other
        > southern sites and third that had already undergone some form of
        > heating. With only minor differences between them, the schedule was
        > designed to encompass all three of the groups we identified. The only
        > real evidences of a different clay source came from two analyses of
        > tablets from Kanesh in Anatolia. All of this does not mean that there
        > aren't groups of tablets that different thermal behaviour, but just that
        > we did not identify any within our collection, which originates mainly
        > from Mesopotamia, but covers most periods.
        >
        > The drying required for larger (thicker) tablets, especially freshly
        > excavated material that could contain significant water [is longer].
        > This can be accommodated by extending the hold period at 140C to maybe 3
        > days. For thick tablets it is also prudent to extend the hold period at
        > 630C, maybe to 24 hours.
        >
        > A higher temperature firing would give higher strength and some of the
        > salts would be removed by glass formation in the fired tablet. However
        > there is considerable risk from calcite degradation between 660 and 720C
        > and the firing schedule would need to be carefully designed to minimise
        > this risk. We have evidence that this is the cause of a large portion
        > of the damage we observe during tablet firing. Also our curators feel
        > that surface texture is an important feature of the tablets (as it aids
        > in making joins) and that over firing alters this. The small number of
        > tablets intentionally firing in antiquity were fired to these higher
        > temperature and another reason for keeping to lower temperatures is that
        > this allows easy discrimination of these intentionally fired tablets
        > from those that have been fired for conservation purposes.
        >
        > Consolidation and Gluing of Cuneiform Tablets
        >
        > Fired tablets are reconstructed with HMG cellulose nitrate adhesive
        > which has been successfully used for more than 30years in the
        > department. It is sometimes necessary to locally consoldiate loose
        > areas, or flakes of tablets or break edges, it is not normally necessary
        > to consolidate the whole surface of a tablet.
        >
        > Tablets which require consolidation are treated in varying
        > concentrations of Paraloid B72 in 50/50 acetone and industrial
        > methylated spirits usually 2 to 10%. The material will only dissolve in
        > acetone the IMS is added to reduced evaportion. The consolidant is
        > pipetted onto the surface and allowed to dry before reapplication. There
        > is a great risk of darkening of the tablet which can be very much
        > reduced by using less volitile solvents or reducing the evaportion of
        > the solvent by placing the tablet in a chamber, overing with glass or
        > wrapping in clingfilm [catering thin plastic film]. B72 has a low glass
        > transition temperature which means the resin will soften around 40c
        > which may be a problem for you, Paraloid B67 has a tg of 50c.
        >
        >
        > --- In _ANE-2@yahoogroups.com_ (mailto:ANE-2@yahoogroups.com) ,
        "larryjhs01" <larryjhs@...> wrote:
        > >
        > > Hello
        > >
        > > I have an UrII tablet in my vast collection, but it is rather fragile
        > > and the clay is beginning to crumble. There is also a bit of salt on
        > > the surface.
        > >
        > > Can anyone in the world of 'cuneiform care' provide me with baking and
        > > other instructions (I can get access to a pottery kiln).
        > >
        > > Thanks.
        > >
        > > Larry Stillman
        > > Monash University
        > >
        >
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
        >
        >





        [Non-text portions of this message have been removed]
      • larryjhs01
        Thank you to everyone for the very helpful advice. Next step is to fire up the kiln...t.uppi ina kinu_ni a$appak... L
        Message 3 of 6 , Jul 7 7:13 AM
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          Thank you to everyone for the very helpful advice. Next step is to fire up the kiln...t.uppi ina kinu_ni a$appak...

          L


          --- In ANE-2@yahoogroups.com, "larryjhs01" <larryjhs@...> wrote:
          >
          > Hello
          >
          > I have an UrII tablet in my vast collection, but it is rather fragile and the clay is beginning to crumble. There is also a bit of salt on the surface.
          >
          > Can anyone in the world of 'cuneiform care' provide me with baking and other instructions (I can get access to a pottery kiln).
          >
          > Thanks.
          >
          > Larry Stillman
          > Monash University
          >
        • Beatrice Hopkinson
          Larry, I don t know if this has ever been done - but it seems to me that if you were to fire the tablet in an electric kiln to harden the clay - you could then
          Message 4 of 6 , Jul 7 9:29 AM
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            Larry,

            I don't know if this has ever been done - but it seems to me that if you were to fire the tablet in an electric kiln to harden the clay - you could then seep the tablet in water to dissolve the salts. But I wouldn't advise doing this unless someone has tried it on something that doesn't matter as much as your cuneiform tablet.

            I am presuming that your tablet has never been sealed in any way and was just sun-dried ? If the tablet was obtained from a site where they were accidentally fired - it could be that the tablet is impervious, in which case the salts will distintigrate it.

            You really need a conservator. But try this basic site to get a little more info: http://www.funsci.com/fun3_en/tablets/tab.htm#2.6

            One more thought is the tablets need to be in a totally moisture proof container.

            Hope this helps - hope someone else will respond with more experience of preserving actual tablets.


            Bea

            Beatrice Hopkinson
            Hon. Secretary Oxford University Soc. LA Branch
            President, DBSAT (Droitwich Brine Springs and ArchaeologicalTrust)
            Board AIA (Archaeological Institute of America)
            Affiliate, Cotsen Institute of Archaeology, UCLA
            818 766 7780


            On Jul 6, 2013, at 1:12 AM, larryjhs01 wrote:

            Hello

            I have an UrII tablet in my vast collection, but it is rather fragile and the clay is beginning to crumble. There is also a bit of salt on the surface.

            Can anyone in the world of 'cuneiform care' provide me with baking and other instructions (I can get access to a pottery kiln).

            Thanks.

            Larry Stillman
            Monash University





            [Non-text portions of this message have been removed]
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