Chemists and conservators: a love/hate relationship

A cathartic experience: There’s nothing more exciting for a conservator such as participating in a conservation course linked to chemistry. We go there with a certain respect (or maybe I should say fear) and the will to be acquainted to a new miraculous reactant that will change our life, at least our professional life.

There is a first stage, the theory explanations, for which one must be mentally prepared. New concepts ought to shake the foundations of the supposedly assimilated ones, and this process involves a high risk of becoming much more confused than before joining the course.
After this puzzling experience there is the practical part, that we attend whishing to have a sort of revelation, such as an apparition of the virgin:  All that molecular frenzy that seems to take place without us being aware of, will reflect into tangible effects in our object?


Conservator and chemist have a special love/hate relationship. Four conservators (left top: Elena Aguado, Flor Cuartero and Clelia Iscla; at the bottom Laura Fuster) in the process of catching all the concepts, trying to see how would they apply those into the artefact, and wondering whether these new concepts might be applicable or not. At the right, the chemist (Richard Wolbers), explaining the practical application of the theoretical ideas and showing a new product.

And the hardest part, alone in our studios: assimilate it, question it, and put it into practice, or rather not. Yet new developments are not always 100% feasible, either because of the application extent[1], or due to the complexity of the treatment, the required resources.

The poor conservator will poorly be able to discuss one to one with a chemist, either about the reactions that happen during the restoration treatments or along the inherent ageing of the artefact; and yet we must call the chemist into question and keep this dialogue alive. Most of all because new techniques lack a contrasted report of long term possible damages, and to use them in cultural heritage might involve irreversible consequences. There are unfortunately enough examples of “magical” new products/treatments which had visible benefits at the first stage, but had undesired results on the long term. For instance soaking parchment in a certain amount of PEG (polyethylene glycol)[2] that after “nourishing” it, it makes it more yellow and translucent, with no option to revert[3] this increasing damage[4].

None of us wants to go down in history as the bibliopath (or grafopath) conservator who applied that fashionable treatment which turned out not to be as good as it seemed. Precisely to avoid this risk, this dialogue is the more and more fluid and continuous, so that the scientific researches are properly adapted to the needs of preservation and conservation of cultural heritage. A multidisciplinary team of conservators, chemists, physicists, biologists (and a long etcetera) working elbow-to-elbow can prevent this disconnection between science and heritage that might have been unsuccessful in some occasions.

But thanks to Richard Wolbers I made peace with chemistry and their scientists. After joining the course Cleaning workshop: Paper bathing/stain removal, at the Polytechnic University of Valencia, my conclusion is that:

  • His precepts have a broad spectrum of application, or would I dare to say that they reach any treatment: cleaning of written supports, both bath or locally; and at the same time, deacidification. And paradoxically to this wide ratio, it is in fact a customized treatment to the particular object.
  • They can be easily executed and do not require unaffordable resources.
  • And the most important: They are soft interventions, very respectful with the artefact and very easily removable, and therefore its innocuousness is almost guaranteed.

I sincerely believe that we are just facing a change of paradigm in our professional approach, and that doesn’t happen everyday day. And you’ll be wondering what on earth has Wolbers explained?!

In order not to annoy non conservators with boring details I will just end this paragraph with an image of the participants to the course, all of us smiling even after three days of macro-polymerisation and hypertonic solutions. But this achievement belongs mostly to Richard Wolbers’ clear explanations and sense of humour. And also to the excellent organisation, which had the final peak with a delicious paella valenciana.

Participants to the workshop Cleaning workshop: Paper bathing and tain removal

Participants to the workshop “Cleaning workshop: Paper bathing and stain removal”, in Valencia (SPAIN), january 2016, lead by Richard Wolbers (right). Image courtesy of the Universidad Politécnica de Valencia.

As for my conservator colleagues, who might still be wondering what the course was about, I refer them to the next post where they’ll find a summary.



Richard Wolbers for his inspiring ideas, bright explanations and sense of humour. And also Laura Fuster (Universitat Politècnica de València) for the best of organisations and translation during the workshop.


[1] For instance the calcium phytate treatment, which is “only” for iron-gall inks (although we must admit the damage is huge, when severe).]

[2] See the recommendation to use it instead of other products in a reference guide by then (RAMP): “The results of these processes (urea and benzol) are not highly successful. (…) In any case, they have been superseded by the treatment described below: This involves treating the parchment with polyethylene glycol, a product which has overcome the problem of hydroscopic stabilization very satisfactorily. (…) The following properties make it ideal for conservation purposes: its pH is practically neutral, it is not volatile and has an acceptable degree of penetrability, it does not provoke microbiological action, it has softening and lubricating properties and, above all, it regulates water as its hygrometric capacity enables it to act as a sponge and, depending on the environmental humidity, it absorbs or releases water while maintaining the stability of its internal constants. Its components (carbon, hydrogen and oxygen) are completely compatible with parchment, as they do not add any extraneous substance. (…) So far no negative effects from the use of polyethylene glycol have been observed, even in artificial ageing tests.

[3] See the claim on a discussion professional group, 30 years after this treatment, to remove PEG from parchment, as it was damaging the document: “A valuable book of our collection (manuscript on parchment) “suffered” a “restoration treatment” thirty years ago, with the help of polyethylene glycol applied by immersion. Would somebody to predict the aging behaviour of this material? Is there any possible treatment to remove this PEG?”  “If the PEG was applied 30 years ago and the parchment sample is displaying increased degradation, then the damage is virtually done so to speak. (…) To slow down the ageing of the parchment, I would suggest keeping it in ideal conditions (dark room, low relative humidity etc.) At this time there is no way to reverse the damage done“.

[4] Related papers describing these damages:

  • Claire Chahine, Christine Rottier. “Study on the Stability of Leather Treated with Polyethylene Glycol”, in ICOM Working Group #10, Conservation of Leather crafts and Related Objects, International Meeting 5.-8.4.1995, Amsterdam.
  • Claire Chahine, Christine Rottier. “Influence Du Vieillissement Artificiel sur le Cuir et le Parchemin Traités au Polyéthylène Glycol”, Les Documents Graphiques et Photographiques–Analyse et conservation, Travaux du Centre De Recherche sur la Conservation des Documents Graphiques 1994-1998, Direction des Archives de France (Editor), Paris 1999.

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