P

 

Pamphlet

A short book composed typically of less than 100 pages and usually given only a paper cover.

Paper

Paper is a matted or felted sheet of predominantly cellulose fibres, formed on a fine screen from a water suspension of the fibres. Papers can be hand or machine made. Traditional Western papers were made from cotton or linen rags. Modern papers are made from wood fibres. The type of wood pulp used to make the paper will influence its expected lifespan - alkaline papers are usually more stable than acidic papers; groundwood papers contain high amounts of lignin and have a short lifespan. Chemical wood pulp papers can be made to very high standards of quality. Japanese or oriental papers are made by traditional methods from a variety of plant fibres - they are valued for their properties of flexibility, strength and (sometimes) permanence.

Paste

An adhesive made from starch or flour such as rice or wheat, generally prepared by heating together a mixture of starch and water and subsequently cooling the resulting product. This in turn may be diluted with water to produce the required texture. PVA can be added to the paste to give an adhesive with fast drying and strength where long term reversibility is not required.

Permanence

The stability of a material and its ability to resist chemical deterioration - not a quantifiable term.

Permanent

See archival. A permanent paper is one that conforms to an agreed standard, is usually acid free and made to resist changes to a greater degree than is usual in other papers.

pH

In chemistry, pH is a measure of the concentration of hydrogen ions in solution, which indicates the acidity or alkalinity of the solution. The pH scale runs from 0 to 14, with each number indicating a 10 times differential. 7 is pH neutral, numbers below 7 indicate increasing acidity and above 7 increasing alkalinity. Alkaline buffered storage materials used in libraries and archives typically have a pH above 7 and below 9.

Phase box

A simple, economical ‘4 flap’ wrap-around box designed to provide an acceptable degree of protection to its contents without undertaking full conservation treatment. Initially developed to provide intermediate protection to materials awaiting further treatment, but now used as a preservation procedure in its own right.

Phased preservation

Collections maintenance activities such as the provision of simple boxes, folders or protective enclosures, rehousing and other preventive preservation procedures, while establishing priorities for future treatment.

Photochemical degradation

Damage caused or increased by exposure to light.

Photographic Activity Test.

To ensure its suitability for the storage of photographic materials, ProLong® Archival Paper passes the Photographic Activity Test ISO 14523:1999(E).

The Photographic Activity Test (PAT) was developed by the Image Permanence Institute in the USA to test the quality of photographic storage materials.

Materials that pass the PAT provide the highest degree of protection for photographs. As such, ProLong® Archival Paper is safe to use in direct contact with stored or displayed photographs.

Plasticiser

A chemical added to another material to give it increased flexibility. In some plastics such as PVC, plasticisers leach out in time and leave the material brittle. Adhesives for use in preservation should be 'internally plasticised'.

Point

A unit of measuring the thickness of paper or board. One point equals 1/1000th on an inch, sometimes referred to as a ‘mil’. Metric based measurements are based on the micron. 4 mil is equivalent to 100 microns.

Polyester

The common name for the plastic polyethylene terephthalate. Its characteristics include transparency, lack of colour, high tensile strength, and chemical stability (when made with no coatings or additives). Used in sheet or film form to make folders, encapsulations, protceive pockets and book jackets. Trade names include Mylar and Melinex. Used in web form ('Reemay') to support paper during wet treatments, and as a relatively non-stick surface through which moisture can pass during mending, drying etc.

Polyethylene (PE)

In its pure form, a chemically stable plastic material. Used in film form for a variety of purposes, including film negative holders and page protectors. A cheaper alternative to polyester film.

Polymer

In chemistry, a large organic compound made up of a series of smaller repeating units joined together by chemical bonds in a regular way.

Polypropylene (PP)

In its pure form, a chemically stable plastic material. Used in film form as for polyethylene. Used in sheet form for boxes, folders and such. Cheaper alternatives to polyester film and archival cardboards.

Polyvinylacetate (PVA)

A plastic usually abbreviated as PVA. A colourless, transparent solid, it is used in adhesives which are themselves also referred to as PVA or PVA adhesive. There are many varieties of PVA adhesives. The types referred to as 'internally plasticised' have greater chemical stability, and are preferred for use in preservation. PVA adhesives are often used in an emulsion form such as the commonly used woodworking or craft 'white glue'. They have a milk-like appearance, but dry clear.

Polyvinylchloride (PVC)

A plastic usually abbreviated as PVC, or sometimes 'vinyl'. Not as chemically stable as some other plastics, and can break down to emit acid components that damage susceptible materials such as paper. Added chemicals called plasticisers are used to make PVC more flexible. These also damage library and archive materials.

The Polyweld process

It is important that the sealing of the polyester is as permanent as the polyester itself, which is why each product is hand-made on the patented Polyweld machine. Polyweld is a method of sealing the edge of the polyester sheets without using any adhesives, solvents or additives of any kind. Through heat, this method 're-extrudes' the polyester to provide a seal that is as strong as the original material, with a unique smooth, rolled edge.

Preservation

Activities associated with maintaining library, archival or museum materials for use, either in original physical form or in some other format. Preservation is a broader term than conservation: conservation activities form part of a total preservation program. Preservation includes both activities taken to repair or treat damaged materials (retrospective) and activities taken to prevent or delay material becoming damaged (preventive preservation).

Pressure sensitive tape

Sometimes called 'sticky' tape. An adhesive tape that attaches to a surface when pressure is applied. The adhesive frequently degrades leaving a brown residue that stains and makes paper brittle. Not recommended for materials intended for long-term preservation. Some archival adhesive tapes are safer to use, but caution should still be exercised especially on very valuable materials.

Preventive preservation

All the management activities undertaken to prevent or delay material becoming damaged, including control and monitoring of the environment; disaster response planning; and staff and user education

Psychrometer / sling psychrometer

A simple instrument used to measure temperature and relative humidity. Sling psychrometers are relatively inexpensive to purchase compared to dataloggers and thermohygrograph, but are very accurate when used properly.

Pulp

Fibrous materials, generally from plant materials including trees, used in the manufacture of paper or board. Groundwood pulp, which is produced by mechanical methods, contains high amounts of lignin and has poor durability. Groundwood pulp is typically used to produce newsprint, which is not intended to have a long expectancy. Chemical pulp has a considerable amount of non-cellulosic material including lignin removed during processing, and the resultant paper has a higher durability than groundwood paper. Permanent papers and boards can be made from chemical pulp.

PVA

See polyvinylacetate.

PVC

See polyvinylchloride.