Te Papa's Blog

In our last post we discussed the process of testing to identify the most appropriate cleaning solution to remove the surface dirt layer from the painting.

After finding the best cleaning solution for the painting the surface cleaning can begin, but we always carefully monitor our progress to ensure that the cleaning solution is working effectively without any adverse effects for the painting.

We generally begin in the lighter areas of the composition, because we can see the progress best in these areas and it allows us to get a feel for the action of our cleaning solution.  We hand-roll cotton wool swabs on bamboo sticks and slightly dampen the swabs with the cleaning solution.  The damp swabs are rolled across the surface of the painting and the dirt is lifted and removed from the surface.  We stop rolling the swab once it appears dirty.  We don’t want to roll the dirty swab across the surface because the particles which collect on the swab may be abrasive.  Because this painting is so dirty we had to change our swabs quite regularly!

Here are some nice photos to show you the progress of the surface clean.  You can see the difference that removing this layer has on the colours, tone and depth in the painting.

We begin by expanding our test areas. This rectangle is the first area of the painting to be cleaned. Photograph taken by Melanie Carlisle. © Te Papa.

We continue by expanding the rectangle. The removal of the surface dirt layer is revealing the depth in the composition. Photograph taken by Melanie Carlisle, 2011. © Te Papa

The cotton wool swabs are changed after a few rolls across the surface. We filled three jars of swabs completing this treatment. Photograph by Melanie Carlisle, 2011. © Te Papa

Katherine and I working on the painting. Photograph taken by James Kirk, 2011. © Te Papa.

Cleaning progressed from right to left. In this detail the difference between the dirty and the cleaned sections is distinct. Photograph taken by Katherine Campbell, 2011. © Te Papa.

The cleaning is almost there! The top left of this detail is all that remains of the surface dirt layer. Photograph taken by Melanie Carlisle, 2011. © Te Papa.

Katherine works cleaning the top left corner. Photograph taken by Melanie Carlisle, 2011. © Te Papa.

The painting after the surface cleaning. The varnish layer still hides the true colours and tones, but already we see a great improvement. Photograph by Melanie Carlisle, 2011. © Te Papa.

There has been a significant change in the appearance of the painting and Poedua is looking much better already!  The removal of the surface dirt layer has revealed the varnish layer beneath it.  The varnish is yellow, discoloured and uneven.  The next stage of the treatment is to remove this varnish layer.  This is the most complicated stage of the treatment.

After completing our technical examination of the painting, taking lots of pre-treatment photographs and writing the condition report, we write a treatment proposal for the painting.  We consider the current condition of the painting and what we would like to achieve with different treatments.  Our proposal is discussed with the curator and together we outline the aims and objectives of the treatment.  No cleaning of a painting is without risk so all options need to be discussed.

The treatment schedule for Poedua begins with surface cleaning the reverse of the painting.  Methods of surface cleaning fall into one of two categories; Dry, where brushes, tweezers, erasers and/or sponges are used to lift and remove surface dirt from the surface; or Wet, where aqueous solutions, solvents or gels are used to lift and remove the surface dirt.  Generally for paintings on canvas we begin with cleaning the reverse of the painting using dry surface cleaning methods.

For Poedua the cleaning of the reverse of the canvas occurred in a number of stages.  It began all the way back in November when the painting was still in London.  To prepare the painting for travel, dust and debris were removed from the area between the canvas and the bottom stretcher member.  This was removed because the pieces could have moved around during transit and caused damage.

A pile of dust removed in London before the transit of the painting. The debris included straw fragments and an old nail. Photograph by Melanie Carlisle, 2010. © Te Papa

Forward a few months and the painting is in the conservation lab.  We carefully lay the painting face down onto a clean table and use a brush and an indirect vacuum (holding a vacuum on low power above the canvas rather than touching the canvas with the vacuum) to remove the loose dust and dirt particles.  

Dusting the reverse of the canvas with a brush and indirect vacuum. Photograph taken by Katherine Campbell, 2011. © Te Papa

This was only partly successful so we cleaned further using small pieces of dry cleaning sponge to lift dirt that was caught in the interstices of the canvas weave.

Katherine cleans the reverse of the canvas with a dry cleaning sponge. Photograph by Melanie Carlisle, 2011. © Te Papa

Finally we removed more dust and debris which was caught between the canvas and the bottom stretcher member.  It was impossible to complete this part of the treatment in London because of the restrictions of materials, time and place.  We held the painting up at the bottom edge and left the top edge resting on the table to allow the dust and debris to fall away from the painting.  We used a variety of tools to carefully remove as much as possible from this area.   

As I hold the painting, Katherine uses a palette knife to gently dislodge dust and debris caught between the stretcher member and the canvas. A pile of dust can be seen on the table top. Photograph by Matthew O'Reilly, 2011. © Te Papa

Our treatment of surface cleaning the reverse of the canvas has resulted in the inscription being clearer and easier to read.

In the centre of this photo the canvas has a grey appearance where it is yet to be cleaned. The P of Poedua has been cleaned and is clearer and easier to read. Photograph by Katherine Campbell, 2011. © Te Papa

Poedua (Poetua), daughter of Oreo, chief of Ulaietea, one of the Society Isles, 1785, Webber, John (1750–1793). Purchased 2010. Te Papa

Welcome to the first blog to keep you up-to-date with the conservation treatment of John Webber’s portrait of Poedua.  Katherine Campbell and I, the two paintings conservators here at Te Papa, will aim to post fortnightly on the progress of our work, offering you insight into what happens to a painting during a conservation treatment.

The painting arrived in the paintings conservation lab shortly after being taken down from display in Toi Te Papa.  Our first task was to remove the painting from the frame and to remove the temporary backing board which had been attached to the reverse of the painting for the transit from London to Wellington.  This is done in order to gain unimpeded access to the whole work, from the front and back of the canvas.

Katherine examining the painting with a hand-held microscope, 2011, Photograph by Melanie Carlisle. © Te Papa

One of the most important aspects of a conservator’s job is documentation; we need to clearly record the current state of the artwork or object.  For a painting, this documentation is generally broken down for each of the paintings ‘layers’.  We begin at the auxiliary support (in this case the wooden stretcher), the primary support (the twill canvas), the ground layer (or priming, preparatory layer), the paint layer and the surface coating.

This report includes a detailed description of the layers, covering visual appearance and the artist’s technique; we also consider what materials were available to the artist and often reference colourmen’s catalogues from the time and place the painting was executed.  We also document the current condition of each layer, with possible reasons behind that condition and any ongoing issues of deterioration.   

It is this documentation that we have been working on for the past few weeks which will help inform us about what treatments to undertake.  We use a variety of different technical examination techniques to aid us in finding out as much as possible about the painting. 

Some of these techniques include examining the painting with different forms of illumination; using normal lighting sources, we look at the painting in reflected, raking and transmitted light.  We use UV lamps in a dark room to investigate the surface coating and any later additions by a previous restorer.  We use infrared photography to see through the paint layer and identify (if they are present) preparatory drawings as well as artists changes (pentimenti), damages and associated restorations.  We examine the individual brushstrokes using a stereo-microscope and get to know all the fine details in the painting.  We use these photographic images to help illustrate and complement the written condition report.

Infrared photograph - detail, 2011, Photograph by Michael Hall. MA_I227737. © Te Papa. The small red circle at the bottom shows the changes the artist made to the scale of Poedua's little finger (pentimenti). The larger red oval shows an area where the paint layer has been damaged and covered with a previous restorers overpaint.

Ultra-violet photograph of Poedua, 2011, Photograph by Melanie Carlisle © Te Papa - This image shows the auto-fluorescence of the natural resin of the varnish when exposed to ultra-violet light. The brushstrokes from the varnish application can be seen. The variation in the auto-fluorescence indicates the uneveness of the varnish layer.

Once this stage of the documentation is complete, we write a treatment proposal to outline what we hope to achieve with our conservation treatment.  The technical examination continues throughout the conservation process, we continue to learn more about the painting and the artist as we spend more time with the painting.