Texte en Anglais, traduction indisponible / Article in English only
Solution to avoid bleaching
When facing a stained document, conservators know there will be little chance that they can get back the original aspect without using bleaching or local whitening.
Such treatments involve chemicals, which, after they have done the whitening job with impressive results, are trapped in the cellulose structure of paper and begin their destructuration job.
People will often speak about « cleaning », but clients should be warned that it has nothing to do with cleaning the paper. Rather, it is a structural modification which makes the paper appear white again, for a while. Usually, this addition of compounds in the structure, will yellow and stain the paper again, in less time than a few centuries did the job in the first place. This accelerate ageing can appear in less than 10 years if the artwork is then exposed to light, or sudden ambiant modifications (humidity and temperature).
What should be known, is that not only the aesthetics are compromised, but this change in structure impacts just as much the cohesion between fibres, and the paper is fragilized by such treatments. It will eventually desagreggate.
Some professionals will say they rinse the paper after a bleaching treatment. While this may be true, even good rinsing will not rewind the structural modification ; it will, at best, slow down the degrading process a little.
I avoid these treatments in my practice as much as possible, and I always warn the clients of the risk taken beforehand. In most cases, people are happy to take the advice, as there is a misconception of what « cleaning » is, and they are just not aware of the consequences.
In some instances, I found that local whitening with amonia solution or calcium carbonate can be a compromise. But I wish to abandon this practice as well.
This is how I have started developping alternatives, and I hope that you too, can get inspired and share your tricks if you just…-can’t…-bleach !
A few months ago, a client came in with a large print that had been stored in a cellar, directly up in the ground. In consequence, the right edge was degraded by mould.
Mould degradation stains the paper with recognizable colors ranging from purple to green – which is especially annoying for artistic objects that are designed for their visual intent. Not only that, but the mold feasts on the sizing (glues used as cohesive link in the paper making process), and the destruction of the size ends up in a flaking, disaggregrating structure with important loss.
Moreover in this case, humidity coming up from the ground brought humidity in the right side of the print, and thus distortion of the paper occured with dimensions modification. In a print such as this, which, nevertheless is in pretty good state, only the entire treatment of the paper would allow for flattening. This is something we chose not to do, because, even if the highly sensitive media had allowed, this means that the entire print would have changed dimensions. Considering the paper nature as well as the design this was not something we thought could be perturbed. Therefore, there would be no flattening of the right edge, and all consolidation treatment would have to be strong enough to reinforce the mold-damaged structure, but with flexible materials to avoid local hardening and further distortion of the area.
> Staining through yellowing or moulding, means that the paper structure has been highly degraded and is fragile. Especially for those reasons, there should be no structural modification through bleaching or local whitening. We chose to intervene in the most minimal way as possible. Here is how we proceeded.
The mould did not appear as active as it had not shown any change after a few years out of the cellar it had stored been in. However, to avoid both mould reactivation, and hardening of the structure, we carefully applied a 2% hydroxypropylcellulose (Klucel G) solution with a pointy brush in the flaking paper, to act as sizing.
Then we thinned down a white Corean paper (wetted and dried beforehand) to level the loss along the edges. It acted as a « cradle » with a trimmed superposition of 1-2 mm behind the edges. We pasted it with 15% Klucel G from the verso. The fact that the Corean paper is extremely white and not toned to match the rest of the artwork is part of the development of this treatment.
The junction behind was locally reinforced with long Tengujo fibers when it felt like it was needed, but not along the full edges to avoid further thickening.
The darkest mould stained areas were covered with a white 5g/cm2 Tengujo tissue, even around the artist’s autograph, held with 2% Klucel G. It just acts as a protection for the next step.
Now comes the interesting part. Normally you would think, I can’t simply cover stains with thin paper and make them disappear because, first, it won’t be enough to cover the stain and it will be see-through, and, second, white just enhances the stain to a grey appearance, even less compatible with the colour of the paper.
Well what if the Japanese tissue acted exactly as what you think, a see-through veil, but instead of letting the stain appear by transparence, the retouch was see-through ?
Wait, what ? Isn’t the retouch supposed to be on top ? Well…what if it…was not ?
Instead of using retouching pigments above the infill, we trapped them between the artwork and the last infill layer. This way, you don’t have to add many layers of paper and paste which woud harden the infill, but instead have one backing paper, and two tissues – one only in some places, and the other on top. They can be thin, because you retouch is going to be consequent, with very little binder, and as such won’t look pasty.
Now the trick is to get as little binder as possible to avoid a pasty, thick result. The idea is that the chalk or dry inert pigments you use remain as powdery as possible to play with visual effect and add maximum light like in a pastel. Adding binder would flatten the effect.
The final tissue that covers the retouch should be toned beforehand to a matching colour to that of the artwork paper. It is pre-glued with Klucel G, then lightly superimposed on the retouch, and most importantly, adhered lightly with gentle brush pressure. Using a teflon tool would crush the visual effect.
Note that the before-treatment picture was taken horizontally, therefore unfortunately for the before-after effect, the distortion appears more on the second picture – taken vertically.
Finally, the print was mounted on tabs from the top, pasted with wheat starch paste on the artwork, and Lascaux 498HV on the acid-free board.
What do you think ? Please let us know or share your own tips in the comment section just below. Thank you for stopping by !
We wish to thank our client for allowing us to use and comment the pictures of this conservation treatment. Anonymous content of the autograph were digitally blurred.