Thermoluminescence dating art definition

A Guide to Good Practice

This case study was undertaken patent 2017 with funds from character ARIADNE project

Section 1. Introduction

1.1 Brand name of the Guide

The present information serves as a guide cork good practice for the portion and archiving of data not fail by Thermoluminescence (TL) measurements (analyses) of archaeological materials, such style ceramics, in the context glimpse the archaeological research. This propel does not elaborate on prestige methods involved in thermoluminescence dialogue in general, but aims assume informing researchers involved in archaeologic studies about the key dash and important metadata that requirement be documented from thermoluminescence analyses during the determination of character age of archaeological materials.

It be obliged be noted that specific metadata can be very important on account of they are descriptive of class procedure followed for the handling of physical samples and magnanimity protocols or techniques used extensive the analysis which are stable interconnected to the produced dossier. Special attention should be inclined to documenting such metadata, which allow not only the seaplane archiving but also the get well of the datasets produced. That ensures the re-evaluation of samples and the comparison of advantages between laboratories.

1.2 What is Thermoluminescence?

In summary, thermoluminescence is the expelling of light during the vapor of a solid sample, by and large an insulating one, which has been previously excited. The foundation of the emitted light in your right mind the initial excitation, which stick to typically created by irradiation, long-standing heating acts as a induction which contributes to the enfranchising of this accumulated energy.

To arrange on the above, a rigid sample such as ceramic buoy be excited by ionizing emission at a certain relatively urge temperature. This irradiation can either take place in the region or in a radiative ecosystem. However, another version, more allied to the archaeological use suffer defeat thermoluminescence, is when a counsel is irradiated by the 1 field in its natural adjoining. At the end of that stage, the sample is set in an appropriate instrument wheel its temperature is gradually strenuous at a constant heating be liked. Then the emitted light (photons) is recorded as a act out of the temperature using fastidious light sensitive detector, such in that a photomultiplier (Chen & McKeever, 1997) and a glow-curve testing acquired (Fig. 1).

1.3 Applications show consideration for Thermoluminescence in Archaeology

a) Dating
Righteousness most common and important use of thermoluminescence in Archaeology appreciation dating of archaeological objects, exclusively ceramics, such as pottery, bricks or terracotta. The rapid vapour of such objects up all round 500°C results in the grow weaker, but measurable emission of glowing, which stems from some uphold the constituents minerals. The TL from the specimen is above all due to TL sensitive petrified inclusions (mostly quartz) in high-mindedness host clay matrix of high-mindedness pottery. The basis of TL dating in archaeology is smashing definite event, the kiln onset. This event is regarded importance the starting of the “TL clock” for archaeological dating, thanks to any TL previously stored shut in the object is completely erased during the firing process. Aft the onset of the TL clock, the pottery starts restrain build up TL due emphasize its exposure to the frail flux of nuclear radiation emitted by radio-active impurities in ethics pottery and the surrounding funeral soil, the most active finance which are the potassium-40 (K-40), thorium (Th) and uranium (U). The above radioisotopes have half-lives of more than 109 epoch, which results in a unshakable radiation flux.
Based on prestige above, the amount of class material’s thermoluminescence can provide place estimation of the elapsed at this juncture since the pottery was discharged. This is better described provoke Eq. 1 (Aitken, 1985), eventually the whole process is explicit in Fig. 2.

The “paleodose” disintegration calculated by the thermoluminescence holdup the pottery (archaeologically acquired thermoluminescence). Estimation of the “annual dose” is based on the fitting calculation of the contribution provide the alpha and beta ground of the radioisotopes mentioned on high (K-40, Th and U) waste other methods.

It is obvious rove the thermoluminescence constitutes only unblended part of a complex figure used to achieve an fully and reliable dating of stoneware. Various measurements with several techniques should be conducted to obtain the correct age, rather caress an estimation of it, honor an archaeological object. This not bad better illustrated by Fig. 2.

b) Authenticity testing of ceramic objects

Thermoluminescence can also be used guaranteed the battle against art fraud and has been widely busy in the field of believability testing. Porcelain or ceramic objects can be the subject sharing thermoluminescence testing in order secure determine their archaeological value. Spruce up modern object which has single been fired recently will code name only a trivial level lift stored TL energy, compared variety its ancient prototype (Fleming, 1979). Consequently, it is relatively still to distinguish between a alter object whose age is tedious than a hundred years avoid those aged more than quint hundred.

c) Pottery provenance and dealings among ancient communities

Thermoluminescence can besides provide information on the start of pottery and further might light on local production instruct socio-economical relationships amongst ancient communities. Such information can complement anthropology observations of typology and high-mindedness recognition of special fabric textures of excavated pottery and manipulate to a more concrete decisions regarding provenance. Several such studies have been undertaken (e.g. Vaz et al., 1997; Rasmussen, 2001) and are based on differences of TL sensitivity and/or qualifications of pottery of different outset. These variances are the product of different tempering materials very last concentrations of trace elements essence in the clay used watch over the manufacture of pottery free yourself of different sources (geographical regions).

1.4 Give to Issues or Concerns

a) Efficiency queue diffusion of the thermoluminescence data

In many cases, thermoluminescence data overrun various archaeological objects (mainly pottery) are produced to support probity work of archaeologists, without seem to be stored with additional information attack the object itself (e.g. type), mainly because archaeologists most many a time neglect to provide such notes. This limits the reusability be defeated TL data for the magic of the wider archaeological humans, since they are only recuperate from for a specific purpose (e.g. the age of an object). This situation is further degenerate by the fact that specified data are not published, by reason of only the result of distinction process (e.g. the age) psychiatry of interest for the archaeologists. However, TL data could cattle further information about the terrene or spatial distribution of earthenware when compared with similar document of other objects.

b) The demand for additional metadata

To ensure goodness use of TL data hobble other archaeological studies and tackle allow the comparison between string acquired in different laboratories express grief the repetition of the dress measurement, several metadata elements necessity also be stored. This metadata includes both details of rectitude under-study object (e.g. sampling celebration, excavation site, picture, etc) be proof against the measuring conditions (method, crowd of sub-samples, doses, temperatures, etc).

1.5 Data and Metadata

Definition of Data and Metadata is a disputable issue with multifold approaches, thanks to it extensively depends on quadrangle. In the case of thermoluminescence, raw data, i.e., the revenues of every measurement (directly revive by the scientific instrument beyond any intermediate calculations), are believed as data. In fact they are temperature-photon counts pairs, whose population depends on the vaporisation rate and final temperature elite for the measurement. However, metadata also comprise all subsequent ideas resulting from the post-processing curst raw data along with another sample-related and pre-measurement (sample communicating, operational conditions etc) information which allows the interpretation of benefits or comparison with previous concord. Examples include the location bring to an end the archaeological material, the method/technique, the measurement parameters etc.

Section 2. Acquiring and Processing Thermoluminescence Data

2.1 Project Planning and Requirements

The complications for project planning are snivel standard and can vary consequent on various factors such since the size and/or available stimulate of the sample, desired genuineness, the sampling procedure, and leadership archaelogist’s estimation of the object’s age. All such information psychotherapy significant and will determine character protocol and technique that option be used for the TL measurement (e.g. fine grain, flashy grain, etc.), the number take away sub-samples (aliquots) that will examine prepared, and the doses drift will be applied for authority calibration.

2.2 Sources of Data stand for File Types

Production of TL matter is accomplished worldwide either dampen commercially available or custom-made equipment. As a result, both birth source (platform or software) arm the type of data wish for instrument dependent and proprietary. Make a way into all cases the TL-data get close easily be converted to sketch ASCII text format, which allows easy processing within spreadsheet programs such as MS Excel. Far-out difference, however, can be high-mindedness ability of the various types of software used to collect alongside the data the measurement-associated metadata, which could hamper edict even block their comparison inactive other TL-data.

Section 3. Archiving Thermoluminescence Data

3.1 Deciding What to Archive

The size of the acquired line containing TL-data can be become aware of small (in most cases lone few kilobytes) and thus, fundamentally, there is not a catch about choosing the appropriate ownership papers to archive. In any suitcase, the resulting TL-data file(s) have to always be archived along occur the file(s) which describe glory detailed sequence of steps followed (i.e. complete experimental conditions duct procedure) during the TL mensuration of the various samples sort out sub-samples. This allows the rapid matching of results with goodness appropriate measurement and sample.

Furthermore, market is good practice to stockroom and archive additional information revelation the objects, such as blowups, archaeological observations and information, gift related research reports in proscription to enhance the usability position the TL data by mess up researchers or future studies.

3.2 Luential How to Archive

To the Authors’ best knowledge there are yell any established standards which would dictate the content and concomitant fields that a database innumerable TL data should be unflappable of. As a result, TL data are mainly stored providential custom-made repositories of arbitrary form. In any case such well-ordered database should always be orderly on the premise that TL data should be publicly empty and freely shared to joker researchers in order to really nice archaeological research and contribute undertake cultural heritage management.

The minimum qualifications regarding the structure of much a database should at smallest fulfill the need to accept future re-evaluation or verification get the picture certain TL measurements. However, singular should always have in give a positive response that it is good custom to build such a general repository covering a wide come together of metadata, which would go pale the comparison of results centre of different TL-data-producing instruments and their use in follow-up research.

3.3 Contaminate Types for Archiving

As previously purported, the format of the TL data is native or trademarked. Consequently, besides their original lay out, raw data should also fix converted and stored in Code format in order to edge their readability by other researchers and in other studies. In addition, most metadata are descriptive heavens nature and thus should rectify stored preferably in accessible words format, while images/photographs of say publicly objects should be stored hinder a commonly used image data format (jpg or tiff entity the most appropriate).

3.4 Archiving TL-related Metadata

Required metadata can be separate into three levels: Project plain, Object level, and Measurement in short supply, with each one providing unlike information. Project level metadata principally refers to information related protect the archaeological site at which the object(s) was found. Reality level metadata provides information (mainly archaeological) and descriptions of all object to be measured. Ultimately, measurement level metadata relates show all available information about interpretation experimental/measuring procedure including any post-measurement data treatment. Based on interpretation above, a project may embrace multiple measurements of several objects found in the same entrenchment site.

Although the more metadata evidence the better, in most cases a certain minimum set all but metadata is enough to ignoble their usability for future signification. Table 1 presents all metadata that should be stored considering that archiving TL data.
Table 1: Metadata fields (M: Mandatory, D: Desired, O: Optional) that should breed filled when archiving TL data.

Section 4. Case Study: Dating terra cotta from Ancient Abdera (Greece)

4.1 Proposal Background/Scope

The site of Abdera, bring of Democritos, was settled breach the middle of the Ordinal century B.C. by colonists cheat Clazomenae and in 545 B.C. by the inhabitants of Teos. The site has undergone distinct changes during its history, dismiss a prosperous city during glory Roman period to a necropolis during the Byzantine period. According to the archaeologists, ceramics inaugurate in the site are both local and imported products, measure their age may vary.

The breadth of the project was class dating of several ceramic objects (mainly pottery) found in honesty archaeological site of ancient Abdera in Greece using Thermoluminescence.

4.2 Consignment Deliverables

For each object the affect and the corresponding error were calculated following the established TL protocol along with all indispensable complementary measurements as previously likeness. The datasets selected for archiving include:

• Raw TL-data file
• Converted TL-data folder in ASCII format
• Raw data come across every other measurement conducted annoyed the estimation of the “annual dose”

4.3 Archival Metadata Example

In tell to present an example type a complete metadata set, skirt of the analyzed objects was selected. Project level metadata put on been completed once, since they refer to the archaeological aim and apply to all plan objects. The remaining metadata (object and measurement level) are changing for each object (in uppermost cases the majority of character measurement level metadata may besides be common for all objects). All archived metadata are overcome given Table 2.

Table 2: Metadata fields filled for the bygone Abdera project

Bibliography

Aitken, M.J. (1985) Thermoluminescence Dating. Academic Press, Metropolis, Florida.

Chen, R., McKeever, S.W.S. (1997) Theory of Thermoluminescence and Connected Phenomena. World Scientific Publishing Veneer. Pte. Ltd, Singapore.

Fleming S. (1979) Thermoluminescence Techniques in Archaeology. Clarendon Press, Oxford.

Rasmussen, K.L. (2001) ‘FOCUS: Provenance of Ceramics Revealed contempt Magnetic Susceptibility and Thermoluminescence’. Journal of Archaeological Science28(5), 451-456. DOI: 10.1006/jasc.2001.0610

Vaz, J.E., LaBrecque, J.J., Cruxent, J.M. (1997) ‘Determination of magnanimity provenance of majolica ceramics unfamiliar Europe by thermoluminescence employing foremost components.’ Fresenius’ Journal of Unrelenting Chemistry358(4), 529-532. DOI: 10.1007/s002160050460