Conserving 16th century royal tapestries
Developing innovative methods of mapping materials and dyes using advanced hyperspectral imaging technology
By Historic Royal Palaces
Dr Constantina Vlachou-Mogire, Heritage Science Manager
The Great Hall, Hampton Court Palace (2022) by Richard Lea-HairHistoric Royal Palaces
Historic tapestry collections have been considered among the most significant forms of art from the 15th to 18th century in Europe. Historic Royal Palaces cares for Hampton Court Palace, and the Royal Collection's tapestry collection that is on display within the palace.
This collection of tapestries was started by Cardinal Wolsey (1475–1530) and then expanded largely by Henry VIII (1509–1547). In the inventory compiled after the king's death, over 2500 tapestries were listed.
Tapestry conservation hyperspectral imagingHistoric Royal Palaces
We are one of the first to develop a new process of using hyperspectral imaging to analyse dyes on historic tapestries non-destructively. This means, we haven't had to take any samples of the historic textile.
Over time, threads can become brittle, fade, tarnish and stretch under strain from environmental factors like light, temperature and the sheer weight of the tapestry itself.
So, it's important to know what materials were used in the making of the original tapestry so we can design conservation approaches that can best protect them for future generations.
Oath and Departure of Eliezer by Pieter Coeck van AelstHistoric Royal Palaces
What is a tapestry?
Tapestries are 'weft-faced' textiles. Supporting plain threads, the warp, are entirely covered by interwoven coloured threads, the weft to produce a design. The types of threads used to make tapestries included wool, silk and metal.
Tapestry threads under microscopy: Wool, Silk, Metal at 235x magnification
Oath and Departure of Eliezer by Pieter Coeck van AelstHistoric Royal Palaces
What materials were used to dye the tapestries?
Analysis of European tapestries showed that a limited number of dyes from natural sources such as plants and insects were used to create a wide palette of colours.
This was achieved by using different mordants (inorganic salts for bonding the dye to the fibre), adding chemicals, or overdyeing a colour with another one (yellow with blue for green).
Hyperspectral Imaging Data Gathering
Using a high-resolution hyperspectral imaging scanner, we captured a section of the tapestry. This instrument collects hundreds of images at different wavelengths for this area which can be up to 1.5m to 1.5m
For each pixel of the area, a hyperspectral image records information covering a wide range of wavelengths between the visible and the near infrared regions of the electromagnetic spectrum, beyond what the human eye can usually see in an image.
Hyperspectral Imaging Data Processing
Initial processing of the visible hyperspectral imaging data using a statistical tool called Principal Component Analysis (PCA) produced a false colour image indicating the mapping of the different dyes on the tapestry area.
Then, processing of the near infrared hyperspectral imaging data using the statistical tool Principal Component Analysis (PCA) produced a false colour image indicating the areas of the different materials used for the production of the tapestry.
The yellow colour in the image represents the metal threads, the blue silk and the red wool.
Tapestry replica fabricsHistoric Royal Palaces
Samples woven from wool and silk yarns representative of historic tapestry materials were created during the European Commission-funded project Monitoring of Damage in Historic Tapestries (2002-2005)
The yarns were dyed using historic dyeing recipes which were found in manuscripts and dyeing books from the 16th and 17th centuries.
As part of this project we scanned the tapestry replica fabrics with the hyperspectral scanner and created a reference library for the materials used to dye them.
Hyperspectral Imaging Data Analysis
Using the information of the MODHT reference materials we processed the hyperspectral image further and identified the dyes used for the production of the tapestry including brazilwood, madder, woad, greenweed and weld.
This is the tapestry as it is seen today under normal light conditions.
Using powerful algorithms this method produced a simulation indication how the tapestry looked like originally. This can be seen, as pictured here, where they yellow and green colour, which have now faded are now more prominent.
Henry VIII's tapestries revealed (2011)Historic Royal Palaces
Watch this video to see how Henry VIII's tapestries looked when he first set eyes on them over 500 years ago. This award-winning tapestry recolouration project was conducted from 2009-10 by conservation scientists from Historic Royal Palaces and the University of Manchester.
Newly upgraded scientific laboratory at Hampton Court Palace (2022) by Richard Lea-HairHistoric Royal Palaces
Our heritage science research continues
The heritage science lab at Hampton Court Palace was upgraded in July 2021 with funding from AHRC's Capability for Collections fund. This funding for new technology boosts our capability to continue our analytical investigations of the historic collections at the palaces.
Story published July 2023.
Constantina Vlachou-Mogire and Kathryn Hallett, Historic Royal Palaces
Vlachou-Mogire, C.; Danskin, J.; Gilchrist, J.R.; Hallett, K. Mapping Materials and Dyes on Historic Tapestries Using Hyperspectral Imaging. Heritage 2023, 6, 3159–3182.
