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Evaluation of methods of chloride ion concentrationdetermination and effectiveness of desalinationtreatments using sodium hydroxide and alkalinesulphite solutionsQuanyu Wang a , Simon Dove b , Fleur Shearman c & Melina Smirniou da Science Group, Department of Conservation, Documentation and Science , The BritishMuseum , Great Russell Street, London, WC1B 3DG E-mail:b Science Group Department of Conservation, Documentation and Science , The BritishMuseum , Great Russell Street, London, WC1B 3DGc Ceramics, Glass and Metals Section, Department of Conservation, Documentation andScience , The British Museum , Great Russell Street, London, WC1B 3DG E-mail:d Stone, Wallpaintings, Mosaics and Facsimile Section, Department of Conservation,Documentation and Science , The British Museum , Great Russell Street, London, WC1B3DG E-mail:Published online: 17 Sep 2010.

To cite this article: Quanyu Wang , Simon Dove , Fleur Shearman & Melina Smirniou (2008) Evaluation of methods ofchloride ion concentration determination and effectiveness of desalination treatments using sodium hydroxide and alkalinesulphite solutions, The Conservator, 31:1, 67-74, DOI: 10.1080/01410096.2008.9995233

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67

Quanyu Wang, Simon Dove, Fleur Shearman andMelina Smirniou

Evaluation of methods of chloride ion concentrationdetermination and effectiveness of desalinationtreatments using sodium hydroxide and alkalinesulphite solutions

AbstractThree methods for determining Cl-

ion concentrations in neutral, alkalineand alkaline sulphite solutions weretested and the results are reported.The Cl- ion - selective electrode wasfound to be the only suitable methodfor alkaline sulphite solutions, andreasons for this are given. Thismethod was further evaluated inpractice monitoring the progress ofdesalination using sodium hydroxideand alkaline sulphite solutions. Thetotal amount of Cl- ions removedduring the treatment was calculatedand the residual concentration in thetreated object measured using ionchromatography.

KeywordsIron, chloride, desalination,silver nitrate, Cl- ion test kit, Cl- ion-selective electrode.

1 Bradley S. Unpublished Internal Report: Thestabilisation of iron, The British MuseumConservation Research Laboratory Report1988/VI.8.

IntroductionDeterioration of archaeological iron is accelerated by the presence of Cl" ions inthe object. Removing chloride from iron objects is currently one of thepredominant approaches to its conservation and preservation. (North and Pearson1978; Gilberg and Seeley 1982; Selwyn and Argyropoulos 2005). Quantitativedetermination of Cl" ion concentration in the treatment solutions is required formonitoring the progress of chloride removal and to determine when thetreatment is considered to be finished. Residual Cl" ions must also be quantifiedfor assessment of treatment efficiency. However, quantitative analysis of Cl" ionconcentration in alkaline sulphite solution, the most commonly used method, iscomplex; it requires oxidation of the sulphite to sulphate and neutralisation ofthe solutions. In the first part of the paper experimental tests on thedetermination of Cl" ion concentration in neutral, alkaline, and alkaline sulphitesolutions are described. The methods tested include silver nitrate titration, achloride test kit and a Cl" ion-selective electrode, and the results are reported.

In the second part of this paper, the Cl'ion concentration determinationmethod established was tested in the conservation treatment practice. Evaluationof the efficiency of sodium hydroxide and alkaline sulphite as desalinationsolutions was carried out. Costain (2000) reported that sodium hydroxide was aseffective as alkaline sulphite in removing chloride, and a lower concentration ofsodium hydroxide or alkaline sulphite could be equally as effective as theconventionally used solutions of 0.5M. Watkinson (1996) reported that alkalinesulphite was more effective than sodium hydroxide alone in his experimentshowever in his paper in this volume he re-evaluates that assessment (Watkinsonand Al-Zahrani 2008). In the past, desalination was carried out in the BritishMuseum using solutions of 0.5M NaOH + 0.5M Na2SO3 with the solutions beingchanged every week. The treatment processes are time consuming and there areenvironmental issues associated with disposal of the solutions.

Evaluation of methods for chloride ion concentration determinationSilver nitrate titration was the first used method in Cl" ion determination; a whitedeposit of AgCl forms when AgNO3 is added to a neutral solution if Cl" ions arepresent. In recent years potential measurement using a Cl" ion-specific electrode(Costain 1985; Carlin et al. 2001; Drews et al. 2004; Bradley1) and potentiometrictitration using a silver electrode (Selwyn 2001) have been used in determination ofCl" ion concentration in desalination solutions. In practice often no measurementwas made and desalination was assumed to be finished following two furtherchanges of solution after the desalination solution became colourless (Bradley1).

To establish a method for routine Cl~ion determination in alkaline sulphitesolution, experimental tests on the determination of Cl~ ion concentration usingsilver nitrate titration, a chloride test kit and a Cl" ion-selective electrode werecarried out.

1 ExperimentalAll tests were carried out on 50ml solutions containing variable Cl"ionconcentrations. The chloride solutions were prepared in (a) neutral solution, (b)alkaline solution (0.5M NaOH), and (c) alkaline sulphite solution (0.5M NaOH +0.5M Na2SO3 with a ratio of 1:1). All chloride solutions were made by diluting

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68 Wang, Dove, Shearman and Smirniou

loooppm aqueous N a d solution to the required concentrations of Cl~ ions using thecorresponding solution, i.e. neutral, the alkaline, and the alkaline sulphite solutions.

2 Silver nitrate titrationIn silver nitrate titration tests, 0.01M AgNO3 was used as the titrant, and a fewdrops of 0.1M K2CrO4 were added to the solution as an indicator. The endpoint ofthe titration in a neutral solution was indicated by the formation of red Ag2CrO4.

Silver nitrate titration is the most popular and low cost method for chloridedetermination in neutral solutions. However, tests have proved that this methoddoes not work in the alkaline conditions of treatments such as the alkalinesulphite method and neutralisation and oxidation have to be carried out prior totitration. The titration itself needs skill and accurate operation, therefore,chloride measurement of the alkaline sulphite treatment solution usingconventional silver nitrate titration was considered impractical for regularmeasurement of desalination treatment solutions.

3 Chloride test kitA commercially available test kit, Aquaquant 14401™ was used. The reagents inthis kit are thiocyanate based and react with the Cl'ions to form orange-redferric thiocyanate. The Cl" ion concentration can be determined by matching thedepth of colour of the tested solution against the colour card provided with thekit. Our tests have proved that the method does not work in alkaline solutionsalthough it does work once the solution has been neutralised; however, due tothe interference of the sulphates the test kit does not work for alkaline sulphitesolutions even after they have been neutralised.

4 Chloride ion-selective electrodeInstrument used in the tests:EDT Ion concentration meter DR359TXCl" ion selective electrode ELIT 8261Reference electrode ELIT 002The specification for the ELT 8261 Cl" ion selective electrode is:Linear measuring range: 3-35,000 ppmOptimal pH range: 1-12Detection limit: lppm

Tests with the Cl" ion-selective electrode were first carried out on neutralsolutions, for which the electrode worked very well. Tests were then carried outon the alkaline solutions and also showed good results, as long as the pH of thesolution met the optimal pH range for the electrode (below 12). Because sulphiteions interfere with Cl" ion measurements they have to be oxidised to sulphate inorder to make the measurement using the electrode. To determine whethersulphate interferes with Cl"ion measurement, solutions of alkaline sulphates(0.5M Na2SO4 + 0.5M NaOH with a ratio of 1:1) containing Cl" ions were testedafter their pH was adjusted to below 12. The results showed that calibration withalkaline sulphite solutions (provided they have been oxidised and neutralised) isneeded to achieve optimal results. According to the manufacturer's instructionsfor the Cl" ion - selective electrode, 0.5ml ion strength adjuster (5M NaNO3 buffersolution) needs to be added to the test solution to compensate for the differentactivity coefficients between solutions if the solutions to be measured areexpected to have a total ionic strength greater than o.oiM, as is the case here.

5 Oxidation of sulphites to sulphatesTwo methods have been reported for oxidation of sulphites to sulphates: heatingthe sulphite solution in a steam bath (Costain 1985) and using hydrogen peroxide(Skinner 1983; Bradley2). To test these methods, experiments were carried outwhich showed that hearing 50ml of the alkaline sulphite to 9OCC for one hour wasnot sufficient to convert the sulphite to sulphate. Even a further hour of heating

2 ibid Footnote 1 did not result in completely oxidation of the sulphite. Heating for a longer period

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Evaluation of methods of chloride ion concentration determination and effectiveness of desalination treatments 69

may result in complete oxidation of the sulphite to sulphate but could causeevaporation of the solutions.

Two sets of 50ml alkaline sulphite solutions, one stored in the laboratory for fivedays and one freshly made were used to test the oxidation of sulphites to sulphatesusing 30% H2O2. The experiments showed that 1.5ml 30% H2O2 was needed forthe stored solution and 3ml for the fresh solution. This indicated that the sulphitewas partly oxidised at ambient temperature during storage. 3ml 30% H2O2 isrecommended for complete conversion of the sulphites to sulphates, becauseexcess HJD^ can decompose, having little effect on the chloride measurement.

6 pH modificationThe alkaline sulphite solutions have pH values of approximately 14 and need tobe neutralised using concentrated HNO3 (Selwyn 2001). A 50ml alkaline sulphitesolution needs approximately 0.5 * 50/16 = 1.5ml of acid to bring it to pHyprovided 16M HNO3 (concentrated, 67%) is used and our experiments haveconfirmed this. It should be mentioned that the pH could change after theaddition of H2O2 and therefore the pH needs to be monitored and adjusted ifnecessary to make sure it falls in the range of 1-12.

7 Summary of the test resultsIn summary, three methods for the determination of Cl" ion concentration inconservation desalination treatment solutions were evaluated experimentally.All of the methods work well for neutral solutions. Alkaline solutions have to beneutralised prior to measurement. Silver nitrate titration and the chloride test kitAquaquant 14401™ do not work for alkaline sulphite solutions. Chloride ionconcentration in alkaline sulphite solutions can be determined by using thespecific Cl~ ion-selective electrode but a small amount of concentrated HNO3

needs to be added to bring the pH of the solution down to below 12 and H2O2

needs to be added to oxidise the sulphite to sulphate. The procedure for the ion-selective electrode measurements can be summarised below:

Calibrate the ion concentration meter using two 50ml standard alkalinesulphite solutions that have been oxidised, pH adjusted, and have had 0.5ml ofthe 5M NaNO3 buffer solution added. For optimal results, the concentration ofalkaline sulphite in the standards should be the same as the treatment solutionsto be measured.

Prepare a 50ml sample for measurement: add 0.5ml 5M NaNO3, 1.5ml 67%HNO3 and 3ml 30% H2O2. The solution volume of the mixture is assumed to be55ml. The Cl" ion concentration [Cl"] of the treatment solution can be calculatedusing the following equation: [Cl"] = 55I / 50, where I is the reading on the meter.

The experiments suggested that the relative errors of the measurements arearound 10%.

Using the ion selective electrode method to evaluate desalination methodsusing sodium hydroxide and alkaline sulphiteIn this section of the paper we discuss the practical desalination of archaeologicalobjects. The aim was firstly to identify whether NaOH alone can be an effectivedesalination solution, and secondly whether the 'standard' method of removingchloride can be modified by using solutions of lower concentrations, and lessfrequent changes of solutions still be equally as effective. Desalination usingsodium hydroxide and alkaline sulphite, in two different concentrations, wascarried out on degraded archaeological iron objects.

1 Desalination treatmentsDesalination treatment was carried out on two batches of Anglo-Saxon ironobjects, one from Dover Buckland cemetery (DBC) in Kent and the other fromGarton Station cemetery in East Yorkshire. Two types of solutions, alkaline(sodium hydroxide) and alkaline sulphite (sodium hydroxide + sodium sulphite)were used for each batch of the objects treated. The DBC iron was treated insolutions of 0.5M concentration, and the Garton iron was treated in solutions of

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7° Wang, Dove, Shearman and Smimiou

Treatmentsolution

0.5M NaOH

o.5MNaOH +0.5M Na3SO3

Objectdescription

Knife

Knife

Knife

Ring

Link

Knife

Knife

Knife

Find No

118

126

147

148

150

430

987

15

Wash!1 week(ppm)

63.6

67.2

139.0

79-3

20.3

12.1

16.2

22.1

Wash 21 week(ppm)

9 1

10.1

414

5.78

5

0.6

2-9

2 4

Wash 31 week(ppm)

9-9

5.6

21.6

54

0.4

O.I

1.6

2-7

Wash 42 weeks

(ppm)

164

8.6

13-5

4-5

1 4

0.7

«

0.6

Wash 51 week(ppm)

4.2

3.0

1.6

2.2

2-9

2.8

1 4

1.0

Wash 6*10 days

(ppm)

6.0

3-2

44

Wash 7*1 week(ppm)

3-7

i-5

3-6

Total Cl"removed

(mg)

329

289

655

386

119

65

93

114

Cl-(wt%)before

desalination

0.09

0.29

NA

NA

NA

NA

0.71

0.23

Cl- (wt%)after

desalination

0.02

nd

nd

nd

nd

NA

nd

nd

Table 1 Concentration of Q ions removed ineach desalination solution (ppm) and CT" ioncontents in flakes post-desalination for DBC ironartefactsnd - not detectedNA - not applicable

Table 2 Concentration of Cl" ions removed ineach desalination solution (ppm) and CT" ioncontents in flakes post-desalination for Gartoniron artefactsnd - not detectedNA - not applicable

"Desalination was terminated for the alkaline sulphite treatment after wash 5

0.1M concentration. Each object was immersed in the solution in a glass containerwhich was sealed and placed into an oven heated to 6o°C. The solutions werechanged at intervals of one/two weeks for each cycle of treatments.

2 Determination of extracted Cl" ions in the desalination solutionsQiloride ion concentration was measured for each solution and the total amountof Cl" ions removed during desalination was calculated. A sample of 50ml ofeach desalination solution was taken for measurement of the quantity of Cl~ ionsremoved after each washing. Prior to the measurement the sample was oxidisedand neutralised in the same way as described above. Desalination treatmentswere terminated after Cl" ion concentration in a treatment solution measuredbelow 5ppm for the second time.

The amount of Cl" ions removed from archaeological iron into each treatmentsolution and the total amount of Cl"ions removed by desalination is listed inTable 1 for the DBC iron, and in Table 2 for the Garton iron. The extraction rate(Cl" removed in each solution / total Cl" removed) is plotted in Figures 1 and 2for the DBC iron and Garton iron, respectively.

Figures 1 and 2 show little difference in extraction rate between the objectsdesalinated in these two types of solutions. Solutions of 0.1M seem to have beenas efficient as those of 0.5M; this is in agreement with results reported bySchmidt-Ott (2006) and Mathias (1994). Sodium hydroxide 0.02M solutions havealso been used for desalination of archaeological iron following plasmareduction by Anderson (2006). Experiments by Schmidt-Ott (2006) showed thatsolutions can be changed fortnightly or even less frequently instead of weekly.Lower concentrations of the desalination solutions and longer intervals between

Treatment solution

0.1M NaOH

o.iMNaOH +0.1M Na,SO3

Object description

Knife

Box fitting

Handle

Spearhead

Knife

Flat strip with nail

Nail with wood

Spoon bit

Find No

GW/q

GW/CV

GW/BH

GW/BQ

GW/AS

GW/BU

GW/BW

GW/AO

Wash 11 week(ppm)

56.6

229.0

634

112.0

70.0

8.1

18.0

72.0

Wash 22 weeks

(ppm)

13.2

32-5

26.1

6.6

64

1-3

4.6

3-2

Wash 31 week(ppm)

2.1

2-5

1.2

2.8

2.0

0.9

2-7

2.6

Wash 42 weeks

(ppm)

1 4

1.1

1 4

1.8

0.8

0.8

0.7

0.9

Total CTremoved

(mg)

46

55

58

78

34

4

2

142

a - (wt%)before

desalination

NA

NA

NA

0.50

NA

NA

NA

0.84

Cl"(wt%)after

desalination

0.01

0.01

O.OI

0.01

0.02

0.01

NA

0.01

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Evaluation of methods of chloride ion concentration determination and effectiveness of desalination treatments

Figure 1 Extraction rates for Cl" removal indesalination solutions from DBC ironDashed lines: desalinated in 0.5M NaOH (A);Solid lines: desalinated in 0.5M NaOH + 0.5MNa2SO3 (AS)

changes can reduce cost and lessen the environmental impact.In our experiments, for most objects, the extraction rate fell to below 10 % after

three weeks. The treatments were terminated within 10 weeks for both batchesof objects. The extraction rate will be dependent on the temperature of thetreatment solution, the size of the object, and the compactness of the surfacecorrosion, and therefore the time needed for desalination can vary.

The trials of treatments suggested the colour of the treatment solution did notnecessarily correlate to the concentration of Cl" ions, nor could it be used as anindicator of the endpoint of the treatment. Dissolution of corrosion products onobject surfaces, some possibly held within structures containing mineralpreserved organic remains, may contribute to the dark colour of some solutions.

3 Residual Cl" ion concentration in the treated objectsThe residual Cl" ion concentration in the treated objects was measured using ionchromatography. Small fragments or loose flakes from the treated object were takenfor the measurements. The pieces were ground as fine as possible, and 5mg wereweighed into a 20ml glass sample tube and suspended in loml deionised water. Thesolution was shaken to avoid uneven distribution of the dissolved Q'ions. 5mlsolution was filtered through a 0.45 um ion chromatography acrodisk filter into anauto sampler vial of 10ml. Each sample was analysed three times and averaged. Thechloride ion contents measured were expressed as weight percentage of the sample.

The effectiveness of chloride removal can be determined by residual Cl" ion

- • -GW/CJ_AGW/CV_A

-GW/BH_AGW/BQ_ASGW/AS_ASGW/BU_ASGW/BW_ASGW/AO AS

Figure 2 Extraction rates for Cl" removal indesalination solutions from Garton ironDashed lines: desalinated in 0.1M NaOH (A);Solid lines: desalinated in 0.1M NaOH + 0.1MNa2SO3 (AS)

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Wang, Dove, Shearman and Smimiou

3 Cleere D. Unpublished Internal Report:Experimental work undertaken on thestabilisation of corroded iron artefacts from theSutton Hoo 2000 Tranmer House excavation,UK. The British Museum CDS report 2005/1/M/1.

4 Smimiou M. Unpublished Internal Report:Desalination of archaeological ironwork — DoverBuckland Cemetery. The British Museum CDSMetals Section report September 2006.

concentration in the small fragments which are, in most cases, deposited aftertreatment of these friable archaeological iron objects. The chloride contents of thefragments post-desalination as measured by ion chromatography are also shownin Tables 1 and 2. The Cl~ ion concentrations in the samples post-desalinationwere either not detectable or around the detection limit (0.05 ppm), and there islittle difference between objects treated with the two types of solutions (alkalineor alkaline sulphite).

It is reported by Watkinson (1996) in his assessment of the chloride extractedas a function of total chloride contained in the object that sodium hydroxide,alone, was a less efficient chloride extractor than alkaline sulphite. In his studythe absolute measurement of residual chloride in the object was obtained bypost-treatment digestion of the whole object. However, this is obviously notpossible for objects in a museum collection. Since sodium sulphite in the alkalinesulphite solution acts as an oxygen scavenger rather than a reducing agent,recent research carried out by Watkinson and Al-Zahrani (2008) suggests that de-aerated sodium hydroxide could be a more effective desalination solution thanalkaline sulphite. Further research on this topic will be carried out as a jointAHRC funded PhD project between Cardiff University and the British Museum.

4 Risk assessment of desalination treatmentsRisk evaluation of desalination treatments was carried out by metalsconservators for both of the treatment pilot groups discussed here. The risks ofwet treatments are well-known and neither of the two treatment variationsdiscussed here were considered risk-free for archaeological iron. Two main riskswere evaluated: that of fragmentation of the object during treatment and thespecific risk to remnant structures containing information such as mineralpreserved organic remains in indirect or direct association with the object. It isthe requirement for the retrieval of full technical information which often resultsin a decision being made by conservators to opt out of desalination regimes astoo risky for consideration.

These studies built on a preliminary report on desalination and subsequentperiodic monitoring of a small group of Anglo-Saxon knives3. For assessment of thepilot groups studied here a series of photographs and X-radiographs enabled aninter-comparison of the general physical condition of objects throughout thetreatment process4. In the Garton group this was combined with examinationunder magnification and micro-photography before and after treatment to detailthe extent and type of mineral preserved organic remains in the upper corrosionlayers. Within the limits of the small size of the pilot groups an inter-comparisonbetween sodium hydroxide and alkaline sulphite as treatment methods was alsomade. Preliminary results confirm what was already known about the degree ofgeneralised risk of wet treatment to fragile iron artefacts. The objects selected for thepilot groups were not uniform and exhibited variable characteristics from functionand manufacture to the degree of mineralization, structural integrity and thepresence of associated organic remains. A proportion was already made morefragile by de-lamination and fragmentation triggered by instability. It is notsurprising that the objects which survived better from long periods of immersion inboth solutions and the contingent risk of changing those solutions were those whichwere in better condition at the beginning of the process. The study did confirm thatdamage and loss to the associated mineral preserved organic remains, as a result ofprolonged immersion in either solution, was not as great as had been anticipated.

It is well understood that technical investigations and options to proceed to wettreatment stabilisation of ironwork requires careful sequencing. It is certainly truethat the level of fragmentation of a proportion of objects in the pilot group put atreal risk the coherence of their associated organic remains. It should also be notedthat as a good proportion of objects in the treatment sample groups were alreadyin a poor condition and some years had elapsed since their excavation, these initialfindings have tended to negatively weight the outcomes in terms of risk. It ishoped the future research will include a full evaluation of the risks as well as thebenefits of desalination treatments to archaeological iron. Risk of desalination to

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Evaluation of methods of chloride ion concentration determination and effectiveness of desalination treatments 73

amphoteric metals such as tin and lead (commonly used as solders, plating andfillers) need to be considered in case they are present in the objects.

5 Evaluation of the desalination treatmentYellow goethite of the 'cotton ball' form reported by Wang (2007) has beenobserved on some of the treated objects, Figure 3. Because it was not there priorto the treatment, it seemed clear that it was due to incomplete rinsing after thealkaline treatment.

The desalinated objects of the DBC group have been placed in storage withoutenvironmental control. Assessment of their condition has been carried out everythree months since October 2006 to monitor the effectiveness of the desalination.It is hoped that by monitoring changes in object condition in conjunction withresidual Cl" ion measurements it will in the future be possible to provide a benchmark quantity of allowable residual chloride for the treated objects to remain ina relatively stable condition. Monitoring during the storage will also provideinformation on whether the yellow goethite can cause further deterioration.

ConclusionsThe Cl" ion-selective electrode was shown to be the best method for routinemeasurement of Cl" ion concentration in alkaline sulphite desalination solutions.It has a detection limit of 1 ppm and accuracy with 10% relative error.Neutralisation and oxidation of the desalination solutions are required prior tothe measurement.

Experiments in desalination using sodium hydroxide and alkaline sulphiterevealed little difference in the efficiency of chloride removal as judged by thechloride extraction rates and the amount of residual chloride on the surface ofthe objects treated. Solutions of lower concentration and less frequent changes ofdesalination solutions were proven to be equally as efficient as the solutions of0.5M with weekly changes. The efficiency of the treatment is also beingevaluated by monitoring changes in condition of the treated objects in storage.Further investigation on the use of de-oxygenated sodium hydroxide solutionsby the AHRC funded PhD student at Cardiff University and the British Museumis already underway. It is hoped that alkaline sulphite solutions can be replacedby sodium hydroxide alone, with the benefits of lower cost, reduced damage tothe environment, and easier monitoring of extracted Cl" ion concentration.

Figure 3 Macroscopic image of goethite in the'cotton ball' form on DBC iron knife No. 126,treated in sodium hydroxide. 'Cottonball' widthapprox. 1.5mm

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74 Wang, Dove, Shearman and Smimiou

AcknowledgementsWe would like to thank Dr. Lyndsie Selwyn of the Canadian ConservationInstitute for kindly providing some of the references on chloridemeasurement. Thanks also go to our colleagues Dr. Philip Fletcher, for theresidual chloride measurement using ion chromatography, Dugyu Cleere,for permission to use her unpublished report, and Susan La Niece for hercomments.

BiographiesQuanyu Wang is currently a conservation scientist at the British Museum.She gained her BSc and MSc in ceramic materials from Tsinghua University,Beijing, China, and PhD in archaeometallurgy from the Institute ofArchaeology UCL, UK. Her research interests are the technology andconservation of archaeological metals. Her recent research projects includethe deterioration of archaeological bronze and iron as well as castingexperiments with archaeologically relevant tin bronzes.

Simon Dove took a Diploma in Conservation at the then Institute ofArchaeology, University of London, in 1965. He joined the Department ofPrehistoric and Romano-British Antiquities at the British Museum as ageneral conservator in 1968, working on a wide range of antiquities notablyshale. In 1975 he transferred to the specialist Metals Section of the newlyformed Department of Conservation at the Museum where he continuedworking for both the merged Department of Prehistory and Europe andlatterly for Coins and Medals, before his retirement in 2007. In addition to hisextensive knowledge of the conservation of artefacts of British and European

archaeological origin he was involved in carrying out numerous wetstabilisation treatments for both lead and iron throughout his long career.

Fleur Shearman graduated from the Courtauld Institute, LondonUniversity in 1979 with a BA (honours) in the History of European Art andArchitecture. She joined the Metals Section of the Department ofConservation at the British Museum in 1980 and gained the MuseumsAssociation Conservation Certificate in Archaeology in 1985. She is anaccredited conservator-restorer and a member of the Accreditationcommittee of Icon representing archaeological conservation. She supervisesstudent interns from the MSc programme at the Institute of ArchaeologyUCL and other European-based conservation courses. Current areas ofresearch are mineral-preserved organic remains on archaeological metals;ancient Egyptian bronze sculpture and Roman silver.

Melina Smirniou received her MSc in 2006 from the Institute ofArchaeology UCL; her portfolio report was on desalination of ironwork andfocussed on Anglo-Saxon ironwork from the Dover-Buckland cemetery.Since graduation she has been employed in the Department ofConservation, Documentation and Science at the British Museum. She is afounding member of the archaeological conservation initiative"Conservators Without Borders" with a key interest in providingsustainable conservation support to disadvantaged sites in cooperationwith archaeologists, specialists and local communities. In addition, she isworking on a PhD that focuses on Late Bronze Age glass production in theEastern Mediterranean.

Contact details:Quanyu WangScience GroupDepartment of Conservation, Documentationand ScienceThe British MuseumGreat Russell StreetLondon WC1B 3DGqwang@thebritishmuseum.ac.uk

Fleur ShearmanCeramics, Glass and Metals SectionDepartment of Conservation, Documentationand ScienceThe British MuseumGreat Russell StreetLondon WC1B 3DGfshearman@thebritishmuseum.ac.uk

Melina SmirniouStone, Wallpaintings, Mosaics and FacsimileSectionDepartment of Conservation, Documentationand ScienceThe British MuseumGreat Russell StreetLondon WC1B 3DGmsmirniou@thebritishmuseum.ac.uk

Simon DoveScience GroupDepartment of Conservation, Documentation and ScienceThe British MuseumGreat Russell StreetLondon WC1B 3DG

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