GELS in the studio

Following a few success stories in the studio using both Wolber’s new aqueous gels and the more established solvent gels, here is a step-by-step guide to the use of solvent gels to remove varnish from a 19th Century Qajar painting.

Detail of Qajar painting, before treatment

Detail of Qajar painting, before treatment

Detail of Qajar painting, after treatment

Detail of Qajar painting, after treatment

 

 

 

 

 

 

 

This painting had a thick yellowed varnish applied overall which fluoresced greeny/yellow in UV, suggesting a natural resin varnish.  This layer was very difficult to remove using free solvents or solvent mixtures. We tested the surface with gelled cleaning solutions to see if through leaving a gel on the varnish surface for a few minutes or through adapting a water-based gel we were able to achieve better results. The most successful cleaning material was Benzyl Alcohol Gel, and here is how you make it…

Solvent gel recipe for polar solvents:

100ml Solvent (in this case Benzyl Alcohol)

20ml Ethomeen C25

2g Carbopol 934

10-15ml deionized water

Make the gel by mixing the Ethomeen, Carbopol and solvent. Add the water gradually using a pipette whilst stirring, the mixture with turn clear and begin to thicken. Stop when the gel is the correct thickness, if the gel goes cloudy you can re-balance it adding a bit more Carbopol/Ethomeen mix. It has a very long shelf life so you can make up a stock gel and leave it on the shelf, ready for testing.

Gel making set-up

Gel making set-up

Measuring out the Carbopol

Measuring out the Carbopol

Measuring out the Ethameen

Measuring out the Ethomeen

Adding water to desired thickness

Adding water to desired thickness

Fully thickened gel

Fully thickened gel

Gel cleaning set-up

Gel cleaning set-up

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It is very important to remember to clear the gel thoroughly, we did this by firstly removing the excess using tissue and cotton wool. The area was the cleared using a 1:2 IMS:White Spirit mixture first and then cleared again with White Spirit. This short time-lapse film shows how the gel was applied:

 

o

We left it on the surface for 5 minutes before removing it and, as you can see, the results are very impressive! Although gels have not replaced solvents in our studio they have certainly helped us to treat a wider variety of surfaces. We hope this helps if you want to try them out too.

New methods of cleaning paintings

 

Richard Wolber course in action

Richard Wolber course in action

The most invasive treatment we undertake as Conservators is often the cleaning of a painting. Historically pictures have been cleaned with water, soaps, wine, bread, reflecting the solubility of a varnish in acidic or alkaline materials. As we have learnt more about the science of our profession, past restorers have recognised that those materials that affected dirt and varnish layers also sometimes affected the underlying paint, therefore cleaning a painting needs to be executed with care and expertise!

Paintings are traditionally cleaned firstly with an aqueous solution, to which a chelating agent is added or its alkalinity adjusted to maximise the removal of greasy or particulate dirt. The second step is to remove the varnish layers (which are often inter-layered with more dirt) using solvent mixtures to dissolve the varnish layers without affecting the paint underneath.

However, treating sensitive acrylic paint films or removing the insoluble old remnants of past retouching campaigns are common problems which traditional methods cannot solve. As scientific analysis evolves to teach us more about the surfaces of both old paintings and contemporary materials, we need to put this research into practice to help us treat them in the studio.

One of our recent learning experiences was to attend International Academic Projects 2014 ‘New Methods of Cleaning Painted Surfaces’ run by the Richard Wolbers, a leader in the development of gelled cleaning systems for paintings. The aim of this course is to offer a more ‘intelligent’ methodology to cleaning a painting, we learnt about adopting the viscosity of our cleaning solutions, changing their isotonicity to reduce swelling, adapting their pH and making emulsions so that the properties of both water and solvents can be brought to a surface in one single application.

In our usually calm conservation world, it was a mind boggling rollercoaster of a training course, leaving us very exited to take our knowledge back to the studio and to begin sourcing all sorts of strange new materials…

Post to follow about how we got on!

Making up different gels

Making up different gels

Frame sample to test with gels

Carbon Dating and the Atomic Bomb

Atom Bomb

At the recent Authentication in Art Conference in the Hague, one topic in particular that stood out was how carbon dating has become an appropriate tool for analysis of objects of recent history.

One of the myriad of scientific tests that can be carried out on cultural objects is carbon dating. This process has been successfully used to date objects generally of a great age such as some previously undatable archaeological finds.

Carbon dating is only carried out on organic material. This material would have absorbed carbon (CO2) in the atmosphere and the amount of CO2 in the atmosphere would be duplicated in this organic material such as human remains, timber framed boats and the canvas and timber used in paintings.

Since mid 17th century it has been extremely difficult to date using this method as the amount of CO2 has been relatively stable. However scientists can now report that there was a peak of excessive CO2 in the mid 1950’s due to the above ground nuclear testing of weapons that was carried out from about 1950 until 1963, when atmospheric nuclear testing was banned, thus making it a surprisingly accurate test for this recent period in our history. Over the last 500 years the date of an object could only be measured with a 50 year span of accuracy whereas now we can pin point accuracy down to a year.

The immediate effect was to almost double the amount of CO2 in the atmosphere, with the peak level occurring in about 1965. The level has since dropped, as the “bomb carbon” (as it is sometimes called) percolates into the rest of the reservoir.
There are also other contributory factors to this rise in CO2 such as the over use of fossil fuels and curiously, cement production.

1280px-Global_Carbon_Emissions.svg