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3.4. Restoration techniques: materials and procedures

There can be no generalization or laying down of rigid principles for restoration techniques, whether for cellulose or any other material, as each document, depending upon its own specific characteristics and the particular problems which it presents will require one type of treatment or another.

But neither could reference be made to a scientific-technical method if no theoretical model existed with a methodology which brings together and co-ordinates all the stages in the restoration of a work.

This is the restoration process model. It constitutes the ideal treatment because it sets out all the possible steps, in a particular order, so that the products and methods applied at one stage do not interfere with those applied either before or after.

The restoration process is governed by guide-lines winch obviate improvization but it must be borne in mind that each work is different and will require the application of one measure or another depending upon the specific needs involved. Taking the theoretical diagram as a starting point and with a "prototype for restoration" in mind, the steps to be taken are the following:

3.4.1 Administrative Control

Restoration begins with the opening of a file or dossier which will accompany the work throughout the process. The history, origin and the data necessary for identification of the work should be recorded in a register.

The dossier may take the shortened form of a standard fiche where the characteristics of the work as well as its state of conservation and the procedures and products used for treatment are recorded. These files, which will begin to be filled in at this stage, will be completed during the restoration process; once this is complete complementary recommendations for future conservation should be included.

A sample fiche might be as follows:

Register No.:   Entry and exit dates:
Object State of conservation: Restoration Process
Technique Losses Mechanical Cleaning
Dimensions Deformations Cleaning with water
Author, title Tears Cleaning with solvents
Place and date Discolouration Deacidification
Deposited by External agents Lamination
  (stains, insects)  

3.4.2 Physical inspection

This inspection begins with an analysis of both the material and cultural characteristics of the work and a real diagnosis is made in identifying the alterations and their causes. Based on this information the treatment most appropriate to the characteristics and the state of alteration of the document is prescribed.

Analysis is carried out with the aid of the sciences applied to restoration work which will determine, on the basis of the physical, chemical and biological tests performed, the nature and state of conservation of the work.

3.4.3 Photography

Photography also forms part of the record begun during the registration stage as evidence of the state of conservation, evolution of the restoration process and the final result (photography with overhead or side lighting, using transparencies). Moreover, it is one of the analytical methods used for identifying particular damage and aspects which are invisible to the naked eye (macro- and microphotography, infrared and ultraviolet photography...)

Another very important role played by photography is as a security measure given the risks involved in any restoration process. It is also used in certain cases as a 'duplicater' of the original (microfilm, microfiche, facsimile...) to prevent deterioration through use. This type of photography for preventive purposes has already been referred to.

3.4.4 Protecting the document

Before commencing specific treatments which involve the use and application of products extraneous to the work to be restored, certain preparation is necessary to that the success of the treatment will be ensured and the original protected against possible risks.

The document must be protected:

(a) During waiting periods; by storage in suitable containers which will afford protection during transport (cases, portfolios, envelopes, bags, etc...):

(b) During treatments involving gases; through appropriate installation on shelves or additional supports, and even use of a stiff or flexible mesh (gauze or open-weave material, plastic grid...) which will act as a covering;

(c) During partial treatments; by covering the area not to be treated with an impermeable, semi-rigid sheet, if possible transparent (e.g. plexiglass);

(d) During treatment in baths; depending on the state of the documents, use of single or double folders of a rigid or flexible material, either permeable or impermeable. In extreme cases of conservation, one side may have to be laminated beforehand. The most commonly used flexible, permeable support is "Reemay". Among the rigid, permeable supports are stainless metal grilles or grids made from a synthetic fibre. The most commonly used material for impermeable rigid supports is transparent plexiglas and for flexible supports, Teflon, polyethylene terephthalate and polyethylene film.

With regard to the protection of inks (fixatives), indications have already been given in the corresponding chapter.

3.4.5 Disinfection and elimination of insects

Whether or not alterations due to biological factors have been detected, every object which enters the restoration laboratory should be disinfected and treated for insects in order to prevent contamination.

The aim is to eliminate the harmful action of insects (insect removal) and micro-organisms (disinfecting). The methods of removing insect pests are usually chemical, i.e. insecticides, fungicides or bactericides depending on whether they destroy insects, fungi or bacteria. When the method used is lethal to any living organism it is termed sterilization.

In the control of pests, there are, apart from chemical products (Table 1) physical and biological methods but these are either still in the experimental stage or belong to the area of preservation.

These chemical products can be applied in the solid state (sublimation), as liquids (spraying or, less frequently, by immersion) and in a gaseous form (fumigation).

Solid products have the lasting effects, but their lethal action is less intense with the result that they are most effective as a preventive measure. The most effective treatment is fumigation but in this case the permanence of the product is very much reduced; a combination of gaseous and liquid or gaseous and solid methods is recommended or a second fumigation may be carried out 15-20 days after the first in case the product does not eliminate insect eggs.

It should be pointed out that all the products used in this treatment are highly toxic, especially the gaseous products, and it is recommended that disinfecting and insect removal treatments should be carried out by specialized personnel.

Fumigation should be carried out in vacuum or pressurized chambers and, the product permitting, in hermetically sealed rooms. Spraying may be carried out in a simpler fashion inside closed containers, all due precautions being taken to avoid leaks.

It must be remembered that these methods (especially the gaseous processes) eliminate the cause of the alteration for the time being but that the origin of insect pests lies in a combination of environmental factors which, if not removed, will lead to a reappearance of the epidemic.

As was indicated in the case of preventive measures, this potential risk must be eradicated using preservation measures which will provide the documentation with the proper microclimate for its conservation.


PRODUCT B F I % Medium X/m3 T Special characteristics
Paradichlorobenzene     X     225g 15d Crystals. Sublimates at 18C. Does not affect eggs.
Paraformaldehyde X X X     5-6g 15d White tablets. Sublimates above 28C.
Timol X X X     30g 15d Sublimates above 20C. 50% R.H. Softens printing inks in some cases.
Formaldehyde 30-40% X X X   Water & ethanol     Inflammable at 50C. Crystallizes below 180C. Often used in adhesives.
- in atmosphere         Water 0.011   Neutralize acidity later with ammonia. 100 cc/1 100 m3.
- in a closed room         250g   24-48h Poor penetrability. Apply at 20C and60% RH preferably.
- in bath         Water   15m  
Pentachlorophenol Sodium Salt X X X 1-5% Water or ethanol 0.1g   In bath, degrades cellulose and may affect colours.
Phenol X X   1% Ethanol 0.01g   In bath, degrades cellulose. Poor penetrability (spray open books).
Orthophenylphenol Sodium Salt X X   1.5% Water 0.01g   In bath degrades cellulose. Used in adhesives
Bendiocarb     X 0.6% Water 24g   Indicated for crawling insects.
N.-phenyl   X   0.5-1% Ethanol & 15m*   Spraying (surface) or bath * (may degrade).
Xylamon     X 50%       Specially for wood. Applied directly by impregnation.
Ethylene oxide X X X 100%   800g 48h Very reactive and dangerous
        12% Anhydrous 100- 48- Not inflammable or explosive, no special
          carbon and Freon 300g 72h chamber required, only container or room that can be sealed.
Methyl Bromide     X     20g 48h Use at 20C and 60-70 R.H. Produces oxidation. Poor penetrability.


B - Bactericide
T - Time
m - minutes
F - Fungicide
d - days
R.H - Relative Humidity
I - Insecticide
h - hours
g - grammes

3.4.6 Cleaning

The concept of cleaning comprises any action aimed at suppressing dirt or adjuncts which will detract from the original appearance or integrity of the document.

The cleaning process employed will depend on the type of dirt that is present.

(a) Mechanical cleaning: specifically used to remove solid particles such as dust. It must always be done before any treatment involving immersion in a liquid is carried out for if the solid particles are not removed beforehand, they may become incrusted in the support.

The process is carried out using dry substances which may act by extracting or removing dust (vacuum-cleaners, compressed air, brushes...) or by abrasion (erasers, glass fibre brushes, fuller's earth, scalpel, erasing machines).

(b) Cleaning using non-aqueous solvents: used preferably to eliminate grease stains and non-aqueous substances. Solvents are applied in a bath or locally (using swabs, blotting paper, colloidal solutions, brushes, drops...).

In the case of organic solvents, precautions must be taken as these products may be explosive, inflammable and toxic.

The most common stains can be removed using the following products:

Varnishes with methanol, ethanol or acetone. Wax - first mechanically and using a heat source, and then using petroleum-ether, chloroform, toluene...Adhesive tape, with 50% chloroform and sulphuric ether; rust stains with 3% oxalic acid, oil-based ink stains using turpentine or dimethylformamide, stamp-pad inkstains with 50% ethanol and acetic acid, ballpen and marker inks using ethanol, diethylene glycol or polyethylene glycol, aniline stains with ethanol and grease stains using perchlorethylene, petroleum ether, dimethylformamide, turpentine...

When grease stains have become oxidized to such a degree that solvents are ineffective, saponification may be tried if the support is resistant.

Saponification, in general terms, is the conversion of the grease in the stain into soap, which is then removed with water. It is a recent method and has not yet been tried widely; it exposes the document to a high degree of risk as a very caustic substance is used (sodium hydroxide).

A 5% solution of sodium hydroxide is prepared in water at 50C and subsequently the same quantity of alcohol as water is added (this prevents the fibres from swelling). The mixture is applied to the stain with a glass rod and is neutralized using 5% acetic acid. These two operations are carried out alternately until the stain disappears and then the dirt is removed using a blotter. Finally it is neutralized with calcium hydroxide.


  State % Medium Time Observations
Water L 100%     Only effective on soluble acids. No buffer effect, leaves no alkaline reserve.
Calcium Hydroxide S Satur- Water 10m Use supernatant liquid. Low cost, easy to apply, gives
    ated     excellent results. After exposure to air, it is transformed into carbonate.
Magnesium Hydroxide S 1% Water 10m Stimulates growth of micro-organisms. After exposure to air, is transformed into carbonate.
Sodium Tetraborate S 2.5% Water 10-20m Disinfectant, but leaves less reserve than calcium hydroxide and degrades cellulose slightly.
Calcium Carbonate S 0.3% Water 1-2h Bubble C02 slightly to convert into bicarbonate, and immerse. Strengthens action of micro-organisms.
Magnesium Carbonate S 1% Water   As for C. carbonate. Leaves stains on iron particles. Not very permanent.
Barium Hydroxide S 1-2% Methanol 15-30m Antiseptic, toxic, use under extractor hood. After airing, is transformed into carbonate.
Calcium Acetate S 0.2% Water & Ethanol 15-30m 20g/20ml water and rest ethanol. Little reserve. Reduces action of micro-organisms.
Barium Acetate S 5% Methanol 15-30m Toxic. Like calcium and magnesium acetate is transformed into carbonate by exposure to air.
Magnesium Methoxide L 1% Methanol 15-30m Prepared commercially with a vaporizer or in liquid form. Apply when document very dry.
Methyl Magnesium Carbonate S 8% * Methanol 15-30m C02 bubbled through 8% magnesium methoxide at 25C.
Zinc Diethyl L 1 kg for every   3-8d Mass treatment in special vacuum chamber.
    25 kg of paper     Very expensive and dangerous.
Ammonia L     18-48h Expose document to vapours. No buffer effect, reserve or permanence. Discolours some opapers.
Cyclohexylamine S 1g/m3     Highly toxic and explosive. Limited penetration
V.P.D. (Vapour Phase Dacidification S     46-56d Prepared commercially from cyclohexylamine in sachets to be deposited between books or left in containers


S - solid
m - minutes
L - liquid
h - hours
d - days

Should traces of the stain remain these are removed by bleaching with sodium hypochlorite.

(c) Washing: Stains caused by aqueous suspensions or solutions are removed by washing off with water to which other substances may or may not be added, such as surface-active agents, colloidal agents or enzymes.

In general, water-temperature should not exceed 40C and the use of organic suface-active agents (detergent type) is recommended in a proportion of from 0.1-0.5% provided that they are harmless and are subsequently rinsed off. The most common detergents used in graphic document conservation are Lissapol N. Teepol G and Triton X 100.


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