Evaluation of Investigation Techniques

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Wall painting reference samples
Twenty-four wall painting replicas from the Laboratorio per Affresco Elena e Leonetto Tintori were selected for this project. From these, 164 sectors were studied, and of these 45 were sampled for study with invasive methods. The organic binders included in these are limited to rabbit skin glue, casein, whole egg, linseed oil, walnut oil, and gum arabic. In addition, two organic pigments are included: indigo and madder lake.

Investigation Techniques Tested
The majority of investigations tested provide information on organic materials. Occasionally when the instrument was the same, methods providing information on inorganic compounds were also included. The investigations have been grouped according to the sample requirements.

Noninvasive investigations (no sampling required)

Imaging and surface mapping—providing topographic information on areas of the paintings
Point analysis—explores a tiny area of the painted surface

Invasive investigations (sampling required)

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Nondestructive—carried out directly on an unmounted sample without altering it Paradestructive—carried out on a prepared sample (e.g., mounted as a cross section or thin section showing the painting stratigraphy). Preparation procedures may induce physical and chemical alterations and prohibit the recovery of the sample in its original form; however, the same sample may be used for other analytical procedures, such as:

  • Imaging and surface mapping—providing topographic information on an area of the prepared sample (cross section)
  • Noninvasive point analysis that explores a point-like surface of the sample as is or prepared in a cross-section

Destructive—completely consumes the sample analyzed

Following the application of all the techniques to the study of the replicas, these techniques are to be evaluated according to the type of information required. There are four levels of information that are considered criteria for identification of:

  • presence or absence of binder
  • class of binder (protein, lipid, gum)
  • binder identification (egg, glue, casein, linseed oil, walnut oil, gum Arabic)
  • binder identification in mixtures (egg and oil, glue and oil)

The methodology or approach to be developed is not a fixed protocol but rather a range of techniques that can be used to obtain the information required for each type of conservation problem that needs to be addressed.

The results of the evaluation of the techniques will be presented at a Symposium to be held on May 12th, 2006 at the Conservation Center of La Venaria Reale.

List of Investigations

Non-invasive spectroscopic examination of painted surface

Responsible Laboratory (researcher)

Visible & Ultraviolet (Vis & UV) fluorescence photography

Opificio delle Pietre Dure (OPD) (Aldrovandi)

Fluorescence Life Time Imaging (FLIM) and UV-VIS fluorescence spectroscopy

Consiglio Nazionale delle Ricerche Istituto per la Conservazione e Valorizzazione dei Beni Culturali (CNR-ICVBC) (Toniolo);

Politechnico di Milano (PM) (Valentini)

Reflectance spectroscopy in the visible & mid IR (900-2000 cm-1) range (Reflect. Spect.)

CNR-Istituto di Fisica Applicata nello Carrara (CNR-IFAC) (Casini)

FTIR portable (mid-FTIR)

CNR-Istituto di Scienze e Tecnologie Molecolari (CNR-ISTM) (Miliani)



Multi-spectral imaging

Foundation or Research and Technology (FORTH) (Kakoulli);

GCI (Wong)

Invasive, non-destructive examination

Responsible Laboratory (researcher)

Cross section preparation and VIS & UV fluorescence photography

Courtauld Institute of Art (Nevin);

OPD (Lanterna – Lalli)

Micro UV-VIS fluorescence spectroscopy

CNR-IFAC (Picollo)

Fluorochrome, stain and micro-chemical tests

Istituto Centrale per il Restauro (ICR) (Talarico);

The Getty Conservation Institute (GCI)

Multi spectral imaging


SEM-EDX (mapping of P to trace casein & egg)


FTIR reflectance spectroscopy (micro and with ATR)

Courtauld Institute of Art (Nevin);

OPD (Lanterna);

CNR-ISTM (Miliani);

GCI (Khanjian)

Micro Raman spectroscopy

University of Parma (Casoli);


Invasive, destructive examination of isolated portions of sample

Responsible Laboratory (researcher)

FTIR spectroscopy (macro)

CNR-Padua (Fiorin)

Gas Chromatography Mass Spectrometry (GC-MS)

UNI-Parma (Casoli);

UNI-Pisa (Colombini);

GCI (Schilling)

Liquid Chromatography Mass Spectrometry (LC-MS)

Vatican Museum Laboratories (Santamaria)

Last updated: March 2011