Investigating the removal of permanent marker ink from historical parchment, using acetone and benzyl alcohol with Velvesil Plus™ gel.

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By Chanelle Briffa

[Editor's note: this is the first in a series of posts on MA work from our most recent alumni. We've had a lot of interesting work recently; you can read successful MA theses in the West Dean College Library, and some students will be publishing their research.]

Amongst other tests, an important aspect of my MA in Conservation Studies dissertation topic was testing the shrinkage temperature of the parchment sample after treatments were introduced. This helped determine whether the treatment used was damaging the intramolecular bonds of the collagen fibres, thus accelerating the deterioration of the parchment.

This project investigates the removal of permanent marker ink from historical parchment documents (notarial deeds) at the Notarial Archives of Malta.[1] Approximately fifteen years ago, the administrators of the collection documented reference numbers of each deed on the covers using black permanent marker ink. In 2015, conservators attempted the removal of this marker ink using acetone; however, treatment was only partially successful.

Ethical implications were considered: removing the ink marks will not make a document more authentic than when it was marked; in this case, cleaning will enable researchers to study details on the parchment, and help alter the negative attitude adopted due to the ink marks. The ink does not offer information concerning the document. On the other hand, removing the said ink would eradicate an element from the history of the document. The ink has become part of the history of the document, an example of the usage of these documents. In this case, when considering both arguments, helping to alter people's perception and the possibility of preventing future generations from writing on the documents again, is the most concerning factor. This is what encouraged conservators' decision to safely remove the ink.

 

Figure 1: Ink markings on the volumes at the Notarial Archives of Malta.

Six historical parchment fragments from the Notarial Archives were employed as test substrates. The skin samples were marked with Stanger® permanent marker ink (research in departmental account books at the Notarial Archives, Malta, suggested that the same brand as that used for the original markings) and conditioned to mimic the humid environment in which the documents were originally kept. Velvesil Plus™ gels with benzyl alcohol, and Velvesil Plus™ gel with acetone, were used to assess the removal of the ink.

In this case, a gel was used as a container to carry the solvent in place. It holds the solvent in place, thus decreasing the rate at which it evaporates at, allowing it more time to penetrate the substrate when compared to applying a solvent without a gel. The choice of gel is important as it determines the type of solvents it can hold. As the gel would rest on the substrate's surface, it is important to ensure that they are not endangering the substrate. Choice of solvents was based on author's previous scientific analysis backed by literature.

Velvesil Plus™ gel is a cross-polymer silicone gel used in the beauty industry and introduced to the conservation world by Wolbers, who suggested its use for porous substrates. Spectrophotometer data and a visual assessment were implemented to identify the effect of the treatment. The shrinkage temperature of the parchment was tested before and after the application of the chosen combinations of gel and solvent applications to determine whether the treatment damaged the collagen structure.

The analytical tests were conducted at the West Dean College analytical lab. Shrinkage temperature tests were conducted at the National Archives at Kew, as West Dean College does not offer such facilities. Sonja Schwoll and Kostas Ntanos kindly helped with the tests.

 

Figure 2: Analysing the fibres while conducting the shrinkage temperature test

A fibre sample of approximately 1mm x 1mm was cut from both the treated areas and from the untreated, un-inked areas of each of the four samples, using a no.15 scalpel blade. This fibre samples was placed on a concave microscope slide, and wetted with deionised water (pH7). The fibres were soaked for approximately 5-15 minutes. This softened the fibres, making it easier to separate individual strands. The sample, still on the slide, was then placed under a microscope with X4 magnification, and the fibres were separated using needles. The fibre separation process took around 15-20 minutes for each sample. After separating the fibres from one another, the concave microscope slide, with the samples still in water, was covered by a borosilicate 18x18 mm flat glass slide. This allowed for the fibres to be examined under a microscope and an area with at least 3-4 loose fibres was focused on for a better analysis of the shrinkage activity. It was not always possible to find 3-4 loose fibres in one specific area, as it was not easy to separate the fibres from each other. However, the tests were still successfully conducted as loose fibre ends were present and visible. (see fig.3)

 

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    Figure 3: Equipment used to separate the fibres and prepare them for testing
    Figure 4: Loose fibre ends used to calculate the shrinkage temperature

    A Mettler Toledo FP82HT micro hot stage, thermostatically controlled by an FP90 central processor, and a Leica DME microscope, with x40 magnification, was used to conduct this test. The equipment was also connected to a desktop computer with recording software called Studio Analyser, which recorded each test. This allowed for the re-evaluation of data, by playing the footage on either Studio player or Windows media player. The video zoom level was 111%.

    The prepared slides were heated on the hot stage, starting at 20ºC with a temperature increase of 2ºC/min, as suggested by Larsen et al.[1] and the Conservation and Restoration of Parchment international workshop.[2] The samples were observed during the heating process, using both the microscope and the computer software.

    Results indicate that the permanent marker ink itself does not actually damage the fibres. The Ts tests of an inked area compared an untreated, un-inked area, from the same sample substrate, were the same at 52.7ºC.

     

    Figure 5: Plotted shrinkage temperatures comparing the temperature of the untreated, un-inked fibres to the two areas tested. The same procedure was repeated for each of the four sample substrates chosen for this experiment. A1is the point at which distinct shrinkage activity can be observed (light blue bar); Interval B1is when the shrinkage activity in one fibre is followed by the activity of another (dark blue bar); Interval C, the shrinkage temperature, is when at least two fibres show shrinkage activity simultaneously and continuously (red bar); Interval B2 is when shrinkage activity slowing down but more than one fibre is still showing activity (dark blue bar); Interval A2 is when distinct shrinkage activity can be observed (light blue bar). Larsen et al (2002) suggests that the accuracy of the Ts measurements is ± 2ºC.The temperature difference when comparing the untreated, un-inked area to the treated areas for every sample substrate is less than that of 1ºC. Thus suggests discrepancy in the Ts result/ data by one degree may be due to human error. (Graph template provided by the National Archives, Kew)

    The Ts of the untreated, un-inked areas did not vary in comparison to those of the treated areas, suggesting that after the treatment, the fibres were in the same condition as they were before. This implies that the treatment did not damage the collagen molecules, thus suggesting that from this aspect, this treatment is safe to apply. Moreover, this supports Gonzales et al's [3] statement when saying that the structural dimension of the parchment substrate returns to its original state after applying a concentration of >70% organic solvent : deionised water (isopropyl alcohol, a polar solvent, was used to conduct this test). These results are also consistent with Woods' theory[4] that suggests that the less polar a solvent is the less likely is it for damage to be inflicted on the fibres.[5] [6]

    The combination of Velvesil Plus™ (silicon cross-polymer) gel and 5% w/v benzyl alcohol was identified as more effective. The Ts test also proved that the treatment did not damage the substrate. It was noted that skin textures affect the degree of success of the removal treatment. Such an issue, along with the complete removal of Velvesil Plus™ gel residues from the parchment substrate, need to be investigated further.

    ____

    [1]Larsen, R. (2002) Microanalysis of Parchment. Archetype Publications. pp.55

    [2]Conservation and Restoration of Parchment, (2008).International Seminar and Workshop [of] Conservation and Restoration of Parchment, pp 44.

    [3]Gonzales, L., Hiller, J.,Terill, N., Parkinson., J., Thomas, K.,Wess,T. (2012) 'Effects of isopropanol on collagen fibrils in new parchment', Chemistry Central Journal, 6, (24), pp. 4

    [4] Woods suggested that non-polar solvents would not be as damaging to the substrate. He states that only polar solvents are damaging, due to the polarity of water.

    [5]Woods, S, C. (2002) 'From skin to parchment', Papier Restaurierung, 3, (4), pp. 16

    [6]Woods, C., Conservation forum. (1995) 'Conservation treatments for parchment documents', Journal of Society of Archivists, 16, (2), pp. 221-238.

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