This repository contains the key raw data analysed and discussed in the manuscript:

A chemometric study of ageing in lead-based paints
Anuradha Pallipurath, Jonathan Skelton, Spike Bucklow and Stephen Elliott
Talanta
DOI: 10.1016/j.talanta.2015.07.037

General:

This repository contains the key raw data discussed and analysed in the above manuscript, including the raw FT-Raman and fibre-optic reflectance spectra, and the output from the various principal-component analyses (PCAs) described in the text and supporting information (SI). Readers are referred to the manuscript for details of the study and methodology. Any data from the paper or SI which is not available in this repository may be requested from the authors.

If you use this data for e.g. further analysis, testing signal-processing algorithms, etc., please cite the following:

A. Pallipurath, J. Skelton, S. Bucklow and S. R. Elliott, Talanta 144, 977-985 (2015), DOI: 10.1016/j.talanta.2015.07.037
J. Skelton, A. Pallipurath, S. Bucklow and S. Elliott, Data for “A chemometric study of ageing in lead-based paints” (2015), DOI: 10.15125/BATH-00120

In addition, if you use spectra of the “Fresh” paint samples in your work, please also cite:

A. Pallipurath, J. Skelton, P. Ricciardi, S. Bucklow and S. Elliott, Journal of Raman Spectroscopy 44, 866-874 (2013), DOI: 10.1002/jrs.4291

These two references contain detailed information about the sample preparation and the spectra collection and processing, as well as analysis of the data, including assignment of the major spectral features.

File-naming convention:

The FT-Raman spectra in this repository are named according to the following convention:
[AgeingState]_[Pigment]_[Binder]_[BinderPigmentRatio]_[LaserPower]_[NumberOfScans]_[SampleNumber].DPT
The fields are as follows:
•	[AgeingState] - one of “Fresh” (as-prepared), “Nat” (aged naturally) or “UV” (acceleratively aged under UV light).
•	[Pigment] - one of “LW” (lead white), “RL” (red lead) or “LTY” (lead-tin yellow); in paintouts of pure binding media, this field is “None”.
•	[Binder] - one of EW (egg white), EY (egg yolk), WE (whole egg), GA (gum arabic), LO (linseed oil), PO (poppy oil) or WO (walnut oil).
•	[BinderPigmentRatio] - denotes samples prepared at extremes of the workable-mixture range for the pigment/binder paint system, with either a low binder-to-pigment ratio (“Lean” in binder) or a high binder-to-pigment ratio (“Rich” in binder); for spectra of the pure binders, this field is “Pure”.
•	[LaserPower] - power of the Raman excitation laser at source.
•	[NumberOfScans] - number of scans integrated to obtain the spectrum.
•	[SampleNumber] - number of the spectrum in the sequence recorded from a given sample.

The fibre-optic reflectance spectra (FORS spectra) are named as follows:

[AgeingState]_[Pigment]_[Binder]_[BinderPigmentRatio]_[SampleNumber].txt

The fields are the same as for the FT-Raman spectra, but do not include a laser power or number of scans, as these parameters are not relevant to the FORS instrument.

Other data in the archive is generally labelled according to which set(s) of spectra were analysed to generate it. The filenames contain a block of the form:

[AgeingState(s)]_[Pigment(s)]_[Binder(s)]_[BinderPigmentRatio(s)]

These fields are as defined above for the spectra files, but may also indicate combinations of ageing modes, e.g. “Nat+UV”, and also of binders and/or binder-to-pigment ratios. Where all binders or ratios were analysed, the word “All” is used in these fields. In some of the PCAs, paint samples made up with proteinaceous or lipidic binders were analysed separately, which is denoted by the terms “Proteinaceous” and “Lipidic”, respectively, in the [Binder(s)] field. In this work, we always analysed paints with the three pigments separately, but it would be possible also to analyse these in combination.
Available data:

1. FTRamanSpectra-*.tar.gz
The raw FT-Raman spectra collected for this study, bundled into three separate groups containing the spectra of the fresh, naturally-aged and UV-aged paints. For convenience, these are provided as TAR archives compressed with the GZip algorithm. These can be decompressed and unpacked with the tar utility on Linux and MaxOS, or the free PeaZip software on Windows (http://www.peazip.org/; last checked 18/07/2015). The spectra files are in the Bruker “data-point table” format, a two-column plain-text file which is easily read by most graphing software.

The archive of “Fresh” spectra also includes files used in a previous study:

A. Pallipurath, J. Skelton, P. Ricciardi, S. Bucklow and S. Elliott, Multivariate analysis of combined Raman and fibre-optic reflectance spectra for the identification of binder materials in simulated medieval paints, Journal of Raman Spectroscopy 44, 866-874 (2013), DOI: 10.1002/jrs.4291

2. FTRamanSpectra-*.tar.gz
The raw FORS spectra analysed in the study, again bundled into three separate groups containing the spectra of the fresh, naturally-aged and UV-aged paints. As with the FT-Raman spectra, these are provided as GZip-compressed TAR archives. The original files output by the instrument software have been converted to a plain-text format containing the spectral data used in the analyses, which should be easily readable by graphing software. The collection of “Fresh” spectra also includes files used in the previous study mentioned above.

3. PCA*.tar.gz
These GZip-compressed TAR archives contain the output of the various principal-component analyses described in the text and supporting information. The format of the filenames is as follows:

PCA-[SampleSet]-[SpectraTypes]-[FTRamanProcessingMethod].tar.gz

The fields are as follows:
•	[SampleSet] - the string identifying the samples used in the analysis (see previous section).
•	[SpectraTypes] - identifies whether FT-Raman and FORS spectra were used either in isolation or in combination as input to the PCA; in this work, combined spectra were used in every analysis, so this field is always “Raman+FORS”.
•	[FTRamanProcessingMethod] - denotes the processing applied to the FT-Raman spectra before analysis, if any; the values used are as follows:
o	“Raw” - the spectra were used as recorded;
o	“BackgroundCorrected” - the spectral-decomposition routine was used to remove the background from the raw spectra;
o	“Chemometric” - the fitted background polynomial and peak functions from the chemometric decomposition were used to generate noise-free versions of the raw spectra;
o	“Chemometric_NoBackground” - the spectra were constructed from the fitted peak functions from the decomposition, with the background functions left out.

Each archive contains three files, where “*” is a placeholder for the fields in the archive name described above:
•	“*-PCWeights.csv” - contains the weights given to the spectral bands in each principal component (PC); the bands are given in ascending order, with FT-Raman followed by FORS.
•	“*-Variance.csv” - contains the variance explained by each of the PCs.
•	“*-Classification.csv” - contains the training spectra projected onto the PCs using the PCA matrix.

The raw data provided accompanies the figures and text in the SI as follows:
•	Fig. 4 (a)/Fig. 5 (a) - “PCA-Nat_RL_All_Both-FTRaman+FORS-BackgroundCorrected.tar.gz”
•	Fig. 4 (b)/Fig. 5 (b) - “PCA-UV_RL_All_Both-FTRaman+FORS-BackgroundCorrected.tar.gz”
•	Fig. 4 (c)/Fig. 5 (c) - “PCA-Nat_RL_All_Both-FTRaman+FORS-Chemometric.tar.gz”
•	Fig. 4 (d)/Fig. 5 (d) - “PCA-UV_RL_All_Both-FTRaman+FORS-Chemometric.tar.gz”
•	Fig. 6 (a)/Fig. S18 (a) - “PCA-Nat+UV_LW_Lipidic_Both-FTRaman+FORS-BackgroundCorrected.tar.gz”
•	Fig. 6 (b)/Fig. S18 (b) - “PCA-Nat+UV_RL_Proteinaceous_Both-FTRaman+FORS-BackgroundCorrected.tar.gz”
•	Fig. 6 (c)/Fig. S18 (c) - “PCA-UV_LW_All_Both-FTRaman+FORS-Chemometric_NoBackground.tar.gz”
•	Fig. S21 (a)/Fig. S22 (a) - “PCA-Nat_LW_All_Both-FTRaman+FORS-Raw.tar.gz”
•	Fig. S21 (b)/Fig. S22 (b) - “PCA-Nat_LW_All_Both-FTRaman+FORS-BackgroundCorrected.tar.gz”
•	Fig. S21 (c)/Fig. S22 (c) - “PCA-Nat_LW_All_Both-FTRaman+FORS-Chemometric.tar.gz”

4. *-BackgroundFunctions.csv
Representative fitted background-polynomial functions for naturally- and UV-aged lead-white paints. The background functions of the “Rich” paint samples (see above) are plotted in Fig. 3 in the article; these files also include the fitted background functions from corresponding representative “Lean” samples for comparison.