How do you wash your tapestries?

Three of the Spangled Bedroom tapestries that were prepared for washing back in November (Tapestrytastic!) safely made their way to Belgium. Siobhan our project conservator made the trip out to see the tapestries go through the washing process.

The De Wit Centre

De Wit Royal manufacturers, founded in 1889, have been restoring tapestries for over a century. At international level, it is one of the world’s leading restorers for museums and private customers. It has combined the use of traditional skills and state of the art conservation techniques to offer a facility that can deal with all aspects of tapestry conservation and restoration.

In the past tapestries were most commonly washed using temporary baths made from polythene and plastic pipes. It required large quantities of softened and deionised water as well as adequate drainage. The tapestry would be fully immersed in the bath and to facilitate efficient soil removal, mechanical action in the form of sponging was essential. In order for the whole surface of the tapestry to receive the same treatment, the tapestry would be rolled on a roller in the bath as the sponging progressed across its entire surface.

Though this method of washing is highly efficient at soil removal, there are drawbacks. The tapestry undergoes considerable physical stress as it is repeatedly rolled and rerolled. Mechanical action and sponging can damage fragile threads. The process is lengthy and drying can take between 12 and 24 hours allowing potentially fugitive dyes to migrate and spread.

Yvan Maes De Wit, the present director, represents the fourth generation of tapestry weavers and restorers at de Wit, and has been responsible for developing a unique system for tapestry washing using aerosol suction. This was patented in 1991 and is the only facility in the world that offers this service.

Diagram from the De Wit website showing the wet cleaning process.

Diagram from the De Wit website showing the wet cleaning process.

This system uses a combination of aerosol spray and vacuüm suction. It is fitted with integral sensors to control pH, temperature, water flow and pressure. The facility consists of an enclosed chamber with glass panels. The base is a large suction table 5 x 9 metres. Ranged across the ceiling are 45 aerosol sprays approximately 1.75 metres above the platform. During the cleaning process the tapestry is held in place by continuous suction. When the aerosol is turned on the chamber fills with water vapour which is drawn down evenly through the entire tapestry.

Start of the washing process

Start of the washing process.

A low concentration of a non-ionic detergent is introduced to the aerosol system for as long as is deemed necessary for soil removal. This is replaced by softened and then de-ionised water during the rinsing process. In cases of extreme soiling sponging can be carried out from a gantry. The tapestry is still held under suction whilst being sponged, therefore there is no possibility of movement which would result in damage to weak areas of silk.

The aerosol/suction combination creates a very even and intense cleaning system with the advantage of the entire tapestry being treated simultaneously. The continuous flow through the tapestry means dirt is loosened from the fibres efficiently and then immediately drawn away avoiding the danger of re-deposition. There is no movement of the tapestry, therefore no mechanical damage from manoeuvring a wet textile can occur. The tapestry is never completely immersed in water thus avoiding dimensional change or shrinkage.

The washing control room

The washing control room

Another good property of continuously working suction is that fabrics that have undergone previous deformation can recover their shape. Irregularities in the fabric can be flattened out when it is dry and immobilised, on the suction table, before cleaning begins. This latter operation together with drying enables the old fabric to recover its original shape.

Finally the full treatment time is quite short. A tapestry measuring 45 m² can be completely dried at 30° in two hours owing to the process of uninterrupted suction over the entire fabric at the same time. If we consider that average cleaning time lasts one hour and rinsing 2.5 hours, the whole cleaning process therefore requires less than 6 hours. Any risk of hydrolysis of fragile fibres is thereby averted and the entire treatment can be constantly supervised throughout a normal working day.

Washing the Spangled Bedroom Tapestries:

Two of the tapestries, one large and one small were laid out on foam to support them on top of the mesh layer of the large suction table. The tapestries were sprayed from the top of the wash chamber, with a mist of soft water and conservation detergent while the suction from beneath drew though the wash liquid.  A sample of the wash liquid is collected throughout the treatment and tested for pH and conductivity.

Sample of the wash water

Sample of the wash water being collected.

The dirt in the tapestries is very acidic, so as the wash progressed this improves and moves toward a more neutral PH. Conductivity measures the ability of a solution to carry a current, the very black dirty water coming off the tapestry at the start of the wash had a high conductivity. This improved as the wash progressed and the water passing through the tapestry became clearer, carrying less particles and ions that could carry a current.

A video microscope mounted on a boom shows the surface of the tapestry and any especially weak areas can be closely monitored. This process lasted for around an hour. It was clear during this process that where there was glue residue on the reverse the water could not be pulled though the tapestry effectively.

Animal glue removed from back of tapestry.

Animal glue removed from back of tapestry.

Once the aerosol spray was turned off the front of the wash chamber was opened and the two conservators from De Wit were able to start gently brushing the tapestries with soft brushes to help loosen and remove the dirt and adhesive. They started by turning off the suction and rolling the tapestry on a large pipe to its centre, this allowed them to spray and brush the reverse of the tapestry rolling back as they went.

Mechanical cleaning of front of tapestry

Mechanical cleaning of front of tapestry.

Mechanical cleaning of tapestry reverse

Mechanical cleaning of tapestry reverse

They then brushed the other half of the reverse in the same way. After they had finished brushing the reverse, the suction and the aerosol spray were turned on for ten minutes to draw through the loosened dirt. After this the aerosol spray was turned off and the front was brush washed, then again the aerosol spray was applied to wash through the loosened soiling. The water used is approximately 26-28 degrees and the warmth allows the animal glue to be softened and removed. This process lasted for about 1 hour.

Following this the tapestries were rinsed for two hours. As samples of the water were collected you could clearly see how the washing process and rinsing had removed the soot, dirt and acidity from each tapestry.

Samples of wash water

Samples of wash water

The suction remained on during the drying process. Very large towels were laid across the top of the tapestries, which were then covered with a thin plastic for about 30 seconds. This process was repeated twice with the towels and twice with absorbent paper to blot a lot of the water out of the tapestries.

Drying the tapestry.

Drying the tapestry.

They were then left to dry at 30 degrees with the suction on for two hours. The complete wash and dry cycle was finished by 7pm. It was then left to rest overnight in situ. The transformation of the tapestry after cleaning was amazing – not only were the colours considerably brighter, with unsightly glue stains removed, but the tapestry was soft and pliable to touch.

The tapestries after drying.

The tapestries after drying.

After drying 4 After drying 5 After drying

Siobhan

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