Paper Conservation: Decisions & Compromises

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Evaluation of stochiometric effects (“side effects” is not an appropriate title) The molar Ca/P ratios of the samples Phy-1 to Phy-4 are similar (0.605 ± 0.05), meaning that in the pH range 4.8 to 6, the CP is deposited in the samples with an average stochiometry of 3.6 calcium atoms per phytate molecule. This suggests that the precipitate is a mixture of Ca:Phytate 3:1, Ca:Phytate 3.5:1 and Ca:Phytate 4:1, consistently with existing data: The Ca:Phytate n:1 is known to be soluble for low values of n (n=1 and n=2), and insoluble for higher n values (2 < n) (Graf 1983). The specification of phytate solutions can be calculated versus pH considering the 12 pKa values of this acid (Heighton et al 2008): In the pH range from 5 to 6, three species of phytate, respectively bounded to four, five, and six protons are co-existing in solution, meaning that resp. eight, seven, and six free sites remain available for calcium bounding. If we consider that each calcium can occupy maximum two available phytate sites, and that calcium does not remove bound protons, the resulting Ca:Phytate precipitate stochiometry should be between 3:1 and 4:1, consistently with the measured value of 3.6:1. In our experimental procedures, the phytate concentration in the solution is 1.75 mM, and the concentration of iron in solution remains below 0.044 mM, a value estimated under the assumption that all iron present in the paper is dissolved. Phytate is also present in large excess compared to iron. In these conditions, its high affinity toward iron is expected to lead to the formation of soluble iron phytate 1:1 complexes, thus facilitating iron removal from the paper in comparison to pure water. This is not the case. Pure water appears the most efficient for iron removal (50 % of iron is lost). On the contrary, iron is more likely to remain in the paper when CP is present in solution (only 30 % of iron is lost). Far from enhancing iron removal from the samples, the CP solution helps to retain iron in the paper. present in low concentration and can be incorporated in the calcium:phytate precipitate without noticeably changing its stochiometry. It was recently demonstrated on quite similar laboratory samples (Rouchon et al 2011b) that the cellulose depolymerisation was mainly due to oxidative mechanisms provoked by surrounding oxygen. Consequently, the poor efficiency of CP treatment, when performed alone (Phy-1 to Phy-4) refers to the fact that phytate does not inhibit iron at this pH level. The ability of phytate to chelate iron is correlated to its capacity to block all iron coordination sites. This property was evidenced in mild alkaline, but not in acidic conditions. In these conditions protons are obviously competing with calcium and iron for phytate bounding. We think that the iron which remains in the paper after CP treatment is only poorly bound to CP and thus not inhibited. When the CP treatment is followed by deacidification, the pH of the paper rises to approx. 8 and approx. two of the protonated sites of phytate become available (Heighton et al 2008), thus favouring the inhibition of iron through chelation. Conclusion This study confirms that the calcium phytate treatment should necessarily be followed by a calcium hydrogencarbonate deacidification in order to achieve long term stability. It additionally shows that the precipitation of calcium phytate in the treating solution does not significantly impact the efficiency of the treatment. We think that iron is not inhibited in the pH range 5 to 6, because it has to compete with protons and calcium ions to bind phytate. After deacidification, the removal of protons releases approx. two new chelating sites on each phytate molecule, which is probably enough to efficiently inhibit iron. In CP solutions, calcium is used at a concentration of 4.4 mM, i.e. in large excess over iron (< 0.044 mM). It is already known that the addition of calcium in iron phytate solutions provokes co-precipitation phenomena (Subba Rao and Narasinga Rao 1983). Similarly, the fact that CP solution helps to retain iron in the paper appears to us related to co-precipitation phenomena. Iron is ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 48
Table 1. List of implemented treatments Name distilled water CP solution CH solution W30 2 baths – – W60 4 baths – – Phy-1 – 2 baths (pH 4.8) – Phy-2 – 2 baths (pH 5.2) – Phy-3 – 2 baths (pH 5.5) – Phy-4 – 2 baths (pH 6) – Bi – 2 baths PhyBi-1 – 2 baths (pH 4.8) 2 baths PhyBi-2 – 2 baths (pH 5.2) 2 baths PhyBi-3 – 2 baths (pH 5.5) 2 baths PhyBi-4 – 2 baths (pH 6) 2 baths The baths were lasting 15 minutes each, and the solutions were renewed between two baths. Endnotes 1 composition of the ink : monohydrate gallic acid (Aldrich, 398225), 0.6 g·L -1 ; heptahydrate Fe(II) sulphate (Aldrich, 215422), 2.66 g·L -1 ; gum arabic (Aldrich, G9752), 6 g·L -1 . 2 Perrier, pH 5.2, composition in mg·L -1 : Ca 2+ , 155; Mg 2+ , 7; Na + ,12; SO 4 2- ,46; Cl - , 25; HCO 3- , 445. Acknowledgment We are thankful to the paper conservator students of the Institut National du Patrimoine, Paris who were involved in some of the samples preparations. References Graf, E. 1983. “Calcium-Binding to Phytic Acid”. Journal of Agricultural Food Chemistry, 31 (4): 851-855. Heighton, L., Schmidt, W. F., Siefert, R. L. 2008. “Kinetic and Equilibrium Constants of Phytic Acid and Ferric and Ferrous Phytate Derived from Nuclear Magnetic Resonance Spectroscopy”. Journal of Agricultural Food Chemistry, 56 (20): 9543- 9547. Neevel, J. G. 1995. “Phytate : a Potential Conservation Agent for the Treatment of Ink Corrosion Caused by Iron Gall Inks”. Restaurator, 16 (3): 143-160. Remazeilles, C., Rouchon Quillet, V., Bernard, J., Calligaro, T., Dran, J. C., Salomon, J., Eveno, M. 2005. “Influence of Gum Arabic on Iron Gall Ink Corrosion, Part II : Observation and Elemental Analysis of Originals”. Restaurator, 26 (2): 118-133. Rouchon, V., Pellizzi, E., Duranton, M., Vanmeert, F., Janssens, K. 2011a. “Combining XANES, ICP-AES, and SEM/EDS for the study of phytate chelating treatments used on iron gall ink damaged manuscripts”. Journal of Analytical Atomic Spectrometry, 26: 2434-2441. Rouchon, V., Duranton, M., Burgaud, C., Pellizzi, E., Lavedrine, B., Janssens, K., de Nolf, W., Nuyts, G., Vanmeert, F., Hellemans, K. 2011b. “Room-Temperature Study of Iron Gall Ink Impregnated Paper Degradation under Various Oxygen and Humidity Conditions: Time-Dependent Monitoring by Viscosity and X-ray Absorption Near-Edge Spectrometry Measurements”. Analytical Chemistry, 83 (7): 2589-2597. Subba Rao, K., Narasinga Rao, B. S. 1983. “Studies on iron chelation by phytate and the influence of other mineral ions on it”. Nutrition Reports International, 28 (4): 771-782. Véronique Rouchon | Eleonora Pellizzi | Maroussia Duranton Centre de Recherche sur la Conservation des Collections, (Muséum national d’histoire naturelle, Centre national de la recherche scientifique, Ministère de la Culture et de la Communication, USR 3224), CP21, 36 rue Geoffroy-Saint-Hilaire, 75005 Paris, France. rouchon@mnhn.fr Correspondence should be addressed to Véronique Rouchon. ICOM-CC Graphic Documents Working Group Interim Meeting | Vienna 17 – 19 April 2013 49
Page 1 and 2: Paper Conservation: Decisions & Com
Page 3 and 4: Content Lieve Watteeuw Introduction
Page 5: Michael Wheeler | Nicholas Barnard
Page 8 and 9: New Trends in Preservation in the D
Page 10 and 11: and monitoring against adverse envi
Page 12 and 13: Steve Hobaica, Patrick Loughney, Ma
Page 14 and 15: The Albums of Duke Charles de Croÿ
Page 16 and 17: Fig. 4: turning the supporting pape
Page 18 and 19: Fig. 2: Close-up of some of the los
Page 20 and 21: manuscript paper, the binding would
Page 22 and 23: Figure 2 partial sewing: the blue d
Page 24 and 25: Books in Exhibitions: History and A
Page 26 and 27: Fig. 4 Museum in London and the pre
Page 28 and 29: Risk and Safety of Illuminated Manu
Page 30 and 31: Fig. 2 Atlas, the Crown papers are
Page 32 and 33: Acknowledgments The authors would l
Page 34 and 35: Verdigris I: Compromises in Conserv
Page 36 and 37: Verdigris 2: Wet Chemical Treatment
Page 38 and 39: Integrated Modelling: The Demograph
Page 40 and 41: Fig. 3: The consequence of 50 insta
Page 42 and 43: Characterisation of Historical Pape
Page 44 and 45: pling is required, tide-lines are c
Page 46 and 47: Study of Phytate Chelating Treatmen
Page 50 and 51: Practice and Progress in the Conser
Page 52 and 53: Fig. 1 Fig. 2 plex picture and prov
Page 54 and 55: Fig. 2: Coloured paper strips place
Page 56 and 57: the fire (on the other hand paper,
Page 58 and 59: inform decisions on conservation tr
Page 60 and 61: This paper summarizes what is known
Page 62 and 63: 2. Methods An interdisciplinary met
Page 64 and 65: Fig. 4: Dyed endpaper pasted at the
Page 66 and 67: Preservation of Architectural Drawi
Page 68 and 69: Notes 1 According Salvador Muñoz V
Page 70 and 71: course of time under the influence
Page 72 and 73: the curators in review of the treat
Page 74 and 75: cellulose powders with cellulose et
Page 76 and 77: Authors Xing Kung Liao Conservator
Page 78 and 79: Fig. 2: Our Railroad Workers and th
Page 80 and 81: The Restoration of Cartoons at the
Page 82 and 83: tation presumes that the works are
Page 84 and 85: To Remove or Retain? - Extensive In
Page 86 and 87: Fig. 4 repeated applications until
Page 88 and 89: The Migration of Hydroxy Propyl Cel
Page 90: tion issue allowed a visualisation
Page 93 and 94: Ethical Considerations Concerning t
Page 95 and 96: emoved with damp cotton swab. Then
Page 97 and 98: Conservation of a Book of Hours fro
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Fig. 4: Pigments movement and conse
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Notes 1 Brazilwood lake, lapis lazu
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pages, which would easily have torn
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The Microflora Inhabiting Leonardo
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Acknowledgments The authors would l
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Microorganisms in Books - First Res
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hyaline white mycelia on and in the
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Deconstructing the Reconstruction E
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Fig. 3: Poster after 2012 conservat
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Conservators’ Investigation of Ch
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had been used, may be false-positiv
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function will provide a holistic pi
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Fig. 2: Patriarchs of Chan Buddhism
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ing techniques, which build upon fu
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Applications of Image Processing So
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Fig. 3 Fig. 4 images in a single wi
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Analysing Deterioration Artifacts i
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Fig. 3 similarity maps. Similarity
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Strategy in the Case of a Wrecked P
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without preliminary consolidation.
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Fiber Optic Reflectance Spectroscop
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Fig. 3: 18 th century paper seal, i
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Fig. 3 Fig. 4 of responsibilities r
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Characterising the Origin of Carbon
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Fig. 3: Sampling depth for ATR spec
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Fig. 2: Filmoplast® tape attached
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Pluchart, F. 1971. Pop Art Et Cie.
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Fig. 3: The reverse of left screen
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porting the reverse of severe creas
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