- Want to know what we mean by protective enclosures?
- Want to know what we mean by archival quality materials?
- Want to know where to find them?
A protective enclosure is the innermost layer of protection surrounding an item (see the 6 layers of protection diagram in blog #3). When well made, of stable archival materials, and designed to properly fit the item, a protective enclosure helps to protect against many of the “agents of deterioration” (see blog #4).
Archival quality materials are designed to retain physical strength and chemical stability over long periods of time. They are made to high specifications and are rigorously tested.
Archival paper and board is acid-free with stable neutral sizing and often a 3% calcium carbonate content to act as a buffer against acidic compounds. It is free from ground wood (mechanically processed wood), lignin (an acidic compound from the cell walls of woody plants that weakens paper if present), and additives such as fillers, coatings and brightening agents; it is chemically processed to remove or neutralise any harmful components. For use with photographs it must pass a Photographic archival storage (PAT) test to ensure it will not harm photographic materials.
Archival papers come in a variety of weights up to 225 g/m2 after which it is defined as board. It is supplied either in sheets or made up into various types and sizes of folder. It is also laminated into thicker box boards and used to make archival boxes to suit different purposes.
Conservation grade mount board is used for mounting and supporting paper items or photographs. It is made from 100% cotton or ‘woodfree’ (mechanical pulp free) fibre and is acid free. It may be buffered or unbuffered (for use with photographs) and is free from lignin, plasticisers and reducible sulphur, this last being particularly important for photographs.
Archival polyester (sometimes referred to by trade names Melinex and Mylar), is a chemically stable plastic film that is free from plasticizers. It is very stable. Another chemically stable plastic is archival polypropylene, not as transparent as polyester, but slightly cheaper to buy. These plastic films are made into sleeves or pockets, and album pages, but must only be used for items that have stable surfaces as they have a static quality, which can attract loose fragments or fragile media.
We recommend you have a look at the catalogues or online shops of archive material suppliers and familiarize yourself with the wide variety of enclosures available. They also have loads of information about their products and the specifications that they meet. You will need to work out what is best for you based on the needs of your collection, the types of solution available and the resources (funds and helpers) you are able to use. Always check the specification though, and make sure it is truly archival!
There are a number of suppliers out there, so have a look round and see what you can find (but do remember to check the spec!). The main ones we use (in alphabetical order – implying no specific recommendation!) are:
- Conservation by Design (CXD)
- Conservation Resources
- Klug Conservation
- Preservation Equipment Limited
- Secol Limited
Watch this space for more support from us on this topic, including illustrations of the sorts of things we use and how we use them.
Based on Gloucestershire Archives Heritage Hub Collection Care training developed by Ann Attwood ACR Collections Care Development Officer and Rachel Wales ACR Collections Care Conservator
At Gloucestershire Archives, through our National Lottery Heritage funded “For The Record” project, we will support people to: “document, care for, interpret and celebrate their personal and shared history”.