Conservation Methods Archives - Page 2 of 4

February 3, 2012October 20, 2022

Tape & Adhesive Removal

The past week we have been looking at tape and adhesive removal, which is a problem that afflicts most collections of paper and books as owners will commonly stick the odd thing back together with tape – the old make do and mend regime – unfortunately, whereas I am usually well up for this way of life, in this scenario, it tends to do more damage than if they were left alone!

P1020401a — Samples of aged tape on paper to work with

The routine for tape and adhesive removal is the same in all cases and starts with backing removal, then the adhesive and finally the stain (if possible).

Backing Material
These will change for different tapes – brown gum tape, cellulose tape, other sticky back plastic, double sided tape, masking tape, scotch tape – the list goes on! The backing material can be removed with a range of different techniques, which each need to be tested until the best method for your tape is found. Any removal should not be done all at once, a bit at a time is less likely to cause any skinning, and the use of a magnified light can also help.

Brown gum tape
This was the hardest to get off as it is not possible without water which can damage the object, even then some skinning occurred with mine. The best method I found was to scrape away the primary surface of the tape using either sandpaper, or better a spatular. I then wet small areas at a time with hot water and a brush and teased away the remaining backing (keep a tissue handy for the residue). At this point it is good to use cellulose powder to get as much adhesive off at the same time to prevent having to wet the paper again at a later date. Unfortunately some cockling did occur in my case and it was a very time consuming method, and one that needs practice to prevent skinning.

A methyl cellulose poultice on top of some bondina on the tape, will also work. This should reduce the water contact, but may still be enough to remove the rest of the backing. I did not try this method.

P1020403a — Teasing brown gum tape with a spatula

Masking Tape
Masking tape will often come off of its own accord quite readily with careful teasing from a spatular. If difficult, it can be warmed up with a hair dryer and this should excite the molecules enough to let the spatular tease it off without skinning. When using this method, it helps to dip the spatular into a solvent to remove any excess adhesive. Easing the spatular carefully along one side and pulling it up with some tweezers will often do the trick. Unfortunately it will then leave a large amount of adhesive that then has to be removed also.

Cellulose tape and other sticky back plastics
Cellulose tape (eg Sellotape) will curl up when put in boiling water, which is how you can tell it apart from other sticky back plastics. Both of my clear tapes were fairly easy to remove, though this would not be the case with any older tapes. In cases such as this, a hair dryer should be set near the tape, allowing it to warm up, then the tape teased away with tweezers as the adhesive softens and becomes more pliable. It is also possible to scarify the surface and add hot water, though the small amount of heat from the dryer is less likely to damage the paper than water. Double sided sticky tape can be treated in the same way.

P1020476a — Using the hairdryer to tease the backing material off

P1020408a — Teasing the tape with a spatular

Adhesive
The remaining adhesive, once the backing material has come off, is more tricky to remove. There are several methods which should be tried in order to find the one that best fits the adhesive. The first step is to use dry cleaning methods, which can often be enough to remove all the tack. If this doesn’t work, solvents are used to swell the remaining adhesive in order to allow it to be removed mechanically. The common solvents are IMS, Acetone, Ethyl Acetate, Isopropanol and Toluene – with the exception of IMS, all of these should be used in a fume cupboard. Toluene is not used in most institutions as it is toxic to pregnant women, so beware! Using each of the methods below, different solvents will need to be tested to see which works best for the adhesive removal.

P1020483a — Using Tolulene in the fume cupboard

Dry cleaning
Cellulose powder is an excellent start for the first stages of removing adhesives, as it is made from loose fibres that are the primary form of paper. When put on the adhesive, the fibres will stick to the adhesive, both can then be manipulated with a spatular and removed. Crepe rubbers are also used in dry cleaning, as they will pick up the adhesive also, though can be quite rough and will damage the paper surface if not used correctly.

Solvent cleaning – method 1, using a poultice
– Place a laponite poultice onto some remay and place that onto the adhesive. Laponite is similar to methyl cellulose (which can also be used) but it is not so wet.
– Feed the poultice with the chosen solvent to allow it to swell the adhesive.
– The solvent can sometimes leek over the poultice and get onto the object, this can be prevented by surrounding the poultice with laponite powder.
– The poultice should be covered with melinex and left for 15 mins, during this time it should be continually fed with the solvent.
– After the 15 minutes are up, the swollen adhesive should then be mechanically cleaned with a spatular.
– Once all adhesive is removed, it will need to be flushed through on the vacuum table.

Solvent cleaning – method 2, using blotter
– A similar method as above, where blotter is used instead of a poultice.
– Cover the object with a small piece of sympotex
– Place blotter on top of this, which has the desired solvent dripped onto it (not drenched)
– Melinex then goes on top of this and it is left for 15 mins, during this time it should be continually fed with the solvent.
– After the 15 minutes are up, the swollen adhesive should then be mechanically cleaned with a spatular.
– Once all adhesive is removed, it will need to be flushed through on the vacuum table.

P1020477a — Making a small solvent chamber with blotter

Solvent cleaning – method 3, using a solvent chamber
This is the most gentle use of solvent as it only uses the vapours, and does not need to be flushed through on the vacuum table.
– Wedge some blotter into the base of a beaker and spray with water to humidify
– Place this upside down over the adhesive area and allow the water vapours to form and reach the adhesive, which may take 10 mins
– Introduce the solvent to the wedged blotter and place back over the adhesive
– Keep feeding the blotter over a 15 min period
– After the 15 minutes are up, the swollen adhesive should then be mechanically cleaned with a spatular.

P1020480a — Making a small solvent chamber

Staining
Staining is the hardest part to remove, and will often have no effect. Rubber adhesives sit on the paper fibres and can be removed to some extent, though acrylic adhesives will get into the core of the paper – the adhesive can be swollen and removed, but stain will remain. The method is to flush through the adhesive with a solvent on the vacuum table, which needs to be done anyway with methods 1 and 2. The object should be placed adhesive down onto some cotton fabric so that it can be absorbed out of the object rather than through it and the area to be flushed should be masked with melinex. Once the vacuum is on, try each solvent, as with the adhesive removal, in order to find the best one. This solvent should be continually fed to the object without letting it dry fully, or get too wet. If it does not remove the stain, it should certainly remove the tackiness.

Tests I have done
Cellulose tape – backing material came off with a hairdryer, the adhesive came off with an Isopropanol poultice and the stain was lightly reduced with Ethyl Acetate.
Gum tape – backing came off by scraping the top surface, then slightly wetting areas and scraping the remainder with a spatular. Cellulose powder got off the adhesive when added immediately whilst it was still damp. There was no stain.
Masking tape – backing cam off with a hairdryer, the adhesive came off with cellulose powder and a crepe rubber. There was no stain.
Scotch tape – backing and adhesive came off from teasing away with a spatular. No adhesive or stain remained.
—
Toluene – This is a good solvent for rubber based adhesives
Ethyl Acetate – Removed some of the stain and a little translucency from adhesive that had made the page transparent.

February 1, 2012January 17, 2022

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.

P1020330a — 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.

P1020332a — 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
—

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.

P1020334a — Calcium Hypochlorite used on a masked out area

P1020359a — 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.

P1020340a — Immersion into a bath of 4% Calcium Hypochlorite

January 22, 2012March 27, 2024

Testing pH

Similarly to the recent post on paste, this is another self indulgent post, designed to remind myself of techniques I have used for the future when my brain starts to forget them!

pH is necessary to test on any number of occasions, for any number of reasons. Our recent washing and bleaching session saw us testing the pH of paper before and after doing experiments on the pages of a book. There are are also various methods of testing pH, though I am only looking at the one here at the moment.

Testing pH using a Probe Meter

Before starting to test the object, the machine must first be calibrated. Once calibrated, it can be used for a day or so, but after leaving for a period of time, it must be calibrated again. The picture shows two pippett jars and two small pots. One jar has an acidic solution with pH of 4, and the second with a neutral pH of 7. A small amount of each solution is put in each small pot and the pippett jars can then be put to one side.

The probe is kept in an airtight pot with a small amount of deionised water to keep it safe. The next step is to remove the probe and dip it into the pH7 pot. At this point the machine should then be altered so that the dial rests on 7. The probe is then washed with deionised water and dipped in the pH4 pot, again the dial should be moved to meet four.

This is repeated until the dial no long needs to be moved. The machine should now be calibrated.

Once calibrated, it is very simple to test the pH. Although one stipulation for this method is that the tested item has to be wet. If testing a dry object, a drop of water can be dropped onto the object and left to soak in. The probe is then rinsed in deionised water and placed on the object, and the reading taken.

Obviously one negative point of this process is that there is the possibility of tidelines, so if it is possible to test whilst humidifying anyway, the risk will be much reduced.

January 19, 2012January 27, 2023

Making Wheat Starch Paste

This is a post I have been meaning to do for a while, both for me to refer to in the future and for anyone interested, and have finally got my act together after a nudge from Sago On Tuesdays! I hope that I may be able to add to it in the future as I learn new techniques. At the moment I only have three or four to list, but they are good ones that I like.

Paste at the V&A

The V&A use shofu paste powder for their paste, it is one of the most refined pastes and is a good tackiness and consistency. It is also not necessary to let it stand like with common paste, it can be cooked immediately.

– Mix 27g shofu powder to 200ml water in a beaker and stir together
– Place the beaker on a hot plate on a medium heat
– Stir for about 15 mins or until the liquid starts to go clear and thicker
– Turn up the heat and continue to stir until the paste is thick enough and stays on the stirrer.
– Cover the beaker with a damp cloth and place in a sink of cold water to cool
(have a cup of tea)
– Once cool transfer the now jelly like paste to a clean beaker
– Fill with water until the paste is all cover and recover with a damp cloth
– This can now be left for a few days on the side (not fridge)
– When using it, take how much you need and sieve it three times
– Do not return served past to the beaker

In this case and all cases where paste is cooked on a hot plate, the paste must be on the heat for at least 35 mins and constantly stirred. This is so that the enzymes can open up and create the tackiness.

Paste at Camberwell College of Arts

Paste at Camberwell is unfortunately the slowest process, but very authentic in terms of how it was made once upon a time. It makes quite a sticky dense paste, with little liquid, which is good for many purposes.

– Mix 1 part paste to 4 parts water and leave to stand for 20minutes
– Poor the mix into the top part of a double boiler (above), and fill the lower part with water
– Set to a high heat and constantly stir until mixture becomes like custard
– Lower the heat and continue to stir until it has been cooked for about 35 mins, it should be clear like silicone
– Leave to cool and then sieve 2/3 times

Paste at the The National Arhives

The National Archives also use shofu paste because of its good qualities, and unlike anywhere else I have been, they also use a saucier, which removes the need of a stirrer! Their paste is also at 20% concentration, which I find a little too liquid, but it is made for everyone, so is what most people there require.

Using a saucier
– Mix 20g of shofu powder with 100/150ml distiller water (dry/wet)
– Put the mixture in the saucier and set to level 4 (out of 5)
– Allow to cook for 30 mins
– Sieve 2/3 times
– Keep in the fridge when not in use

Using a microwave
– Mix 20g of shofu powder with 150ml of water in a beaker
– Microwave at short intervals as below, stirring in the middle
60s/20s/20s
– Sieve 2/3 times

January 16, 2012November 5, 2022

Paper washing and bleaching, vol 1

Bleaching is a dirty word in conservation, one whispered secretly. However there is no denying that there is something roguishly fun about sticking an old page from a book into a bath of bleach and watching it go from brown to bright white! I can state that the Rev will also be seeing some bleaching treatment in the next couple of weeks, and might then go on the wall!).

This is what we have been doing in the last week with Alan Buchanan, a visiting lecturer of ours, who is very charismatic and great to listen to. We have been working very scientifically and thoroughly, ensuring variables were recorded before starting out, and a control kept.

Preparing the paper for washing
Prior to our various forms of cleaning, it was necessary to record the primary data of the paper, so that we could see the difference once cleaned. We were using pages from the same book, so although they varied slightly in weight, they were very similar on most parts. Each sheet was weighed five times at intervals of 20 seconds, and a mean average taken from those recordings. One sheet was kept as a control and has remained unwashed.

P1020277a — The first four pages, ready for cleaning

Washing the paper
Immersion
A simple and straight forward method of cleaning, and one often with satisfactory results as the water will yellow when significant amounts of dirt are removed. Prior to immersion, the page had to be humidified. Immersing a document immediately into water is too much stress for the paper, it needs to be gently introduced to water so that it will accept it more readily. Once humidified we put the page into the water, at about 30 degrees, and left it for 30 minutes. After this, the page came out and was left on the drying rack to dry. In order to flatten it after that, it would need to be humidified again and pressed. Pressing is not something we are doing in our experiments.

P1020282a — Ceder humidification chamber

P1020279A — Immersing the page into 30 degrees water

Float washing
In my opinion, this was the method of washing with the most obvious results as a distinctive residue of dirt left on the blotter. Again, prior to the was, we humidified the page. There are a few methods of float washing including ones where the object is left at an angle and water permanently run underneath it, but Alan assured us that there is no evidence to support one method working better than the other, and in his experience, this was an effective one. In a bath containing two sheets of blotter, water is introduced until it reaches the same level as the blotter, no more. Then the humidified object, recto up is placed onto the blotter. We also left this for 30 minutes. The benefit of this method is that the recto is kept dry, or at least away from the water and relatively untouched, which would be important with fragile media. If the document itself was fragile, it could also be placed on bondina before going on the blotter, which would protect it.

P1020284a — The second page being float washed

P1020298a — The remaining stained blotter

Blotter Washing
The third method of cleaning was the blotter wash, it is an extremely gentle form of washing, should the object have friable media or is delicate in itself. Primarily the first sheet of blotter is lightly wetted, this is a little more needed than for humidification, but not much. At this point both the dry and wet blotter should be weighed. On a clean surface, the dry blotter is placed down, then a sheet of roofing felt (goretex is the more expensive version of the same thing) then the object, recto up, the second sheet of roofing felt, and finally the wet blotter. This should then be covered with a piece of plastic and weighed down to keep the moisture contained. This is then left for an hour or more, as it is a gentle technique and needs time to work. If the object is very delicate, bondina can be used either side of the object. The method works by gravity pulling the water from the wet blotter through to the second, as well as the capillary matting from the roofing felt – this allows vapours through, but not droplets of water. As the second blotter is dry, it will be naturally pulled through to this blotter, via the object, cleaning it in the process. The reason for the object being recto up is so that any matter drawn through the object would show on the verso. Once the hour is up, the blotters are weighed again and there should be a considerable difference in weight.

P1020301a — The cleaning method in action

Washing on the vacuum table
This is not as delicate as the blotter wash, but more so than the other methods. The object must first be humidified before washing to prevent it form being stretched on the vacuum table. The object should be placed on top of a cotton sheet on top of the machine as this will draw the water through quicker and will protect the object. It will also protect the machine from any dirt removed. Once on the table, it can be sprayed gradually all over with water until cleaning is complete.

P1020292a — Setting up the table for washing

P1020295a — The object on the vacuum table

P1020296a — Washing the object with a water spray

Localised and differential washing
We were particularly looking at localised washing with additives such as IMS (Industrial Mentholated Spirits) and Synperonic A7 (detergent that reduces surface tension and cleans).

The solutions were made at 100ml quantities as follows:
50ml IMS and 50ml Water
100ml Water and a drop of Synperonic

These were used in conjunction with the vacuum table. The object had to be humidified prior to being washed on the table. The area needing attention was masked out using melinex and the object placed on top of a cotton sheet. Using a very fine brush, the IMS or Symperonic was added directly to areas such as foxing spots, hopefully reducing them, though it was not massively successful. The object should be placed recto up so that anything that is drawn out through the suction, comes out on the verso.

December 2, 2011March 27, 2024

Making Solvent Set Tissue

Today was the final lecture from our visiting tutor who has been teaching us board reattachment. For her final instalment, we looked at solvent set tissue, which is not completely dissimilar to gelatine set tissue, and can also cross over into the heat set tissue theme as well – a multifunctional tool!

The reasons for using solvent set tissue, are twofold, the first being to be used when a book has such sensative leather that to get any paste or anything containing water would cause darkening – this form of paper repair is completely water free and therefore at no threat of causing this. The second key use is speed, as once set up, the process can be much quicker than using paste and tissue. It does have its downfalls as well, which is why it might not be used all the time – it is more permanent than wheat starch paste, if it gets erectly onto the leather rather than the repair tissue, it cannot be removed.

So the technique is as follows:

Initially tone some tissue in preparation for it to be pasted onto
Get the equipment ready, including a squeegee, a small screen print tray and a water trough to cover them both once used – the adhesive is extremely quick to dry and will not come off once stuck.
Humidify the toned tissue.
Lay the frame onto a sheet of melinex – this is what the adhesive will end up on.
Paste out small batches of adhesive along one edge of the screen and squeegee evenly over the rest of the frame.
Once evenly spread, remove the frame and lay out the toned tissue, ensuring a flat surface.
Allow to dry.
This can then be stored for future use.
When using, reactivate with solvent.

The adhesive used is called Lascoux and is an Acrylic glue. It is of the same family as PVA, though unlike PVA, it is completely non-reversable once dried. It is possible to reactivate the adhesive with solvent once dried, though it will not remove it, just make it sticky again. It is this method that is used to reactivate the adhesive on the tissue when you want to use the tissue on a book.