Tag: techniques and instructions

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Paper washing and bleaching, vol 2

The second part of my washing and bleaching post is more about the bleaching part. As mentioned in the previous post, this is rarely done in conservation as it is thought to damage the structure of the paper fibres and will continue to disintegrate the object if not denatured properly. As before we were also measuring the experiments as we went to see the difference in paper weights as they were cleaned.

Sodium Dythonite (EDTA), Hydrogen Peroxide, Calcium Hypochlorite

There were three forms of bleaching we used in this session – Sodium Dythonite, Calcium Hypochlorite and Hydrogen Peroxide.

Spot testing the different bleaches

Sodium Dythonite at pH8
Conservators will us Sodium Dythonite to a certain extent, and will often prefer this solution, however it is often not removed totally and can leave a residue in the object. Similarly to this, conservators will often reuse this solution on the same spot many time over in order to remove a stain, however this repetitive use of the solution can be much more damaging than using a stronger one, such as Calcium Hypochlorite, to begin with and ensuring it is removed in full.

20g of Sodium Dythonite into EDTA (unknown amount)
Adjust the pH with Sodium Hydroxide until pH 8 is reached
This required a large amount of Sodium Hydroxide, possibly as the strength of the latter and the amount of EDTA was unknown.

Calcium Hypochlorite at pH9 (bleach of choice)
This solution often has a bad name, though we have been told it does not diserve such a reputation. It is argued that chlorine may be left in the object after de-naturing it (washing through with water). This is chemically suspicious as chlorine is linked to calcium and the molecules are strong and generally stay together. Once the calcium is removed, the chlorine will have nothing to attach to and should come off as a gas.

200ml of 4% Calcium Hypochlorite into 600ml of water
Intial testing of pH showed it at pH10.5
10% Acetic Acid was added to bring the pH down to 9

Hydrogen Peroxide at pH9
When it is used on objects, it will bleach as it drys due to unstable H2O2 molecules, which will release the spare O as a gas, denaturing itself in the process. However a conference in Vienna argued that this did not always occur and peroxide was left in the paper causing continual damage, it is therefore no longer used.

3ml of 3% Hydrogen Peroxide into 23ml of demonised water
The pH is altered using Ammonia to reach pH9
This should bring the amount up to 30ml
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We then used each of these bleaches, mostly the Calcium Hypochlorite, and tested methods of cleaning. Everything was done on the vacuum table, having first humidified the object, and thoroughly washing it throughout. We used small amounts on a brush to target small stains such as foxing, and also spraying specific areas by masking the object with melinex.

Calcium Hypochlorite used on a masked out area
Half and half on the same sheet (using bleach of choice)

In the case of immersion, the whole page was put in a bath of Calcium Hypochlorite and then washed in water and left to dry.

Immersion into a bath of 4% Calcium Hypochlorite
Before immersion
After immersion


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Pulp papers with Alan Buchanon

We have recently had a fascinating day with Alan Buchanon on making and using pulp papers for paper repairs as an alternative to japanese and western paper repairs. This is a technique that Alan has honed to a great art and precise formula that allows any conservator to give it a go an come out with a good and useable result.

To start with we made and dyed paper at the same time, this was done using shreds of a high grade of cotton rag paper to make the pulp and a precise mixture of dyes to get the colour. The percentage of the colour is essential a the lower the percentage, the lighter the colour. There were about six colour charts using a different percentage of dye for each chart, these can be seen in the photographs below.

Once the paper was made, we then moved on to making the pulp. By take the object and comparing it to the charts, it was possible to see what colour match the object best. Once found, the chart then gave grammages of how much paper was needed from each colour in that percentage, these could be weighed out and blended together like a recipe!

At this point a pulp was ready, and after making small samples and adding any colours if necessary, we were ready to repair. This was done using a powerful suction table, on which the object sat with the area to be repair masked out of melinex in order to prevent any damage to the surrounding area. Using a pippet, the pulp was then squirted into the area the be mended and built up gradually to the required amount. Once this was reached, the use of a hair fryer would dry out the final parts of the repair, and it was done!

I was unsure how strong these repairs would be as there is no adhesive involved. Alan assured me that the combination of the suction of the table and the hair dryer meant thy the cotton fibres would form a very strong covalent bond with the cotton fibres in the paper. This was not necessarily the same with wood pulp papers, which might need a small amount of adhesive mixed into the pulp to ensure it adheres enough.

Amazing!