Ceramics

Ceramic is a general term referring to objects made of fired clay. The three main types of ceramic are Earthenware, Stoneware and Porcelain. The different types of ceramic body (body is a term which describes the components of the material that the ceramic is made of) exhibit different porosities and strengths roughly depending on the components of the clay and the temperature to which it is fired. Most ceramics are also covered in a glassy layer, known as a glaze; but can also be painted, enamelled and gilded. Ceramic material has long been used to make many different types of decorative and utilitarian objects .Types of Ceramic objects can include table services, candelabras, mirror surrounds, small sculptures, vessels of all types and a variety of small and large decorative pieces.

Causes of damage

Ceramics objects are in general (excluding many types of archaeological ceramics) quite resilient. As inorganic objects they are not generally susceptible to damage from over exposure to light or fluctuations in temperature or relative humidity. Archaeological ceramics are an exception to this, especially if they contain soluble salts. The principle disadvantage of ceramic material is brittleness and it is this property that accounts for the majority of damage to ceramic objects.

Damage most frequently occurs during handling, transportation, and by interference from animals or humans. The correct handling and transport of a ceramic object is crucial to its safety, as accidents can be catastrophic. Objects should be handled carefully and never lifted by handles, spouts, knobs or rims. All cracks and chips and fissures should be carefully noted on each piece as these can ultimately lead to further damage if the ceramics are not handled properly. Pieces should always be carried in padded baskets to avoid breakage. Jewellery that could chip ceramic pieces should be removed before lifting. It is good practice to plan the route, and get someone to help with opening and closing of doors before you lift an object. Objects with more than one component should always be separated during transport - lids should be removed and packed separately and plates should be interleaved with foam or tissue paper to cushion.

The best protection for ceramics is to avoid open display as much as possible and keep objects in display cabinets. Avoid over loaded shelves, as ceramic objects will damage easily if a shelf fails. Also avoid using wire plate hangers altogether and only use plastic covered ones if the plate is completely intact; any use of plate hangers on cracked plates can cause further damage through stress and tension.

Due to their inherent fragility, repairs to ceramics have been undertaken for centuries. Until the 20th century adhesives were not strong enough to use by themselves and physical repairs using dowels and rivets were employed. Now, conservation adhesives of high quality are readily available and can be used without the need to dowel or rivet.

Treatment

The two main treatments for ceramics are cleaning and bonding. Cleaning is an irreversible process and should be undertaken carefully. Sound ceramics can be dry dusted regularly to keep them clean. Glazed pieces can be wiped with a cotton pad dampened with warm water. It is inadvisable to submerge historic ceramics in water as this can cause problems if the object has any hairline cracks or chips. Avoid commercial cleaning products if possible, as these can leave residues not only on the glaze surface but also inside the ceramic body, entering through cracks and chips in the glaze layer. Any such residues could later cause damage to the piece. Extra care should always be taken with gilded porcelain as the gilding, even when fired, has only a weak attachment to the glaze. Archaeological and other unglazed ceramics should always be referred to a ceramics conservator for treatment.

A conservator, who can judge which adhesive would match the body of the ceramic best, should generally undertake repairs. Missing areas can be filled with a variety of materials that can be painted to look like ceramic. While this treatment can restore the aesthetic integrity of a piece, and enable it to be displayed, the object will not be able to function as it did before it was damaged. Generally speaking all liquids must be kept away from repaired pieces – this has implications for use and for cleaning.

If an object breaks, all the pieces should be carefully gathered and wrapped in tissue paper to avoid further damage to break edges and kept safely until a conservator can appraise them. Collect even the tiniest chips, as these can prove invaluable to a ceramics conservator later. Do not tape pieces together or offer up broken edges to each other as this can cause further damage. Avoid trying to repair historic ceramics yourself. Botched jobs will take longer for a conservator to undo and will therefore make the job longer and more costly, and in some cases actually cause further damage.

Storage and display

Storage areas for ceramic objects should be dry and dust free. Plates should be stored vertically, in plastic covered plate racks if possible, or at least interleaved with conservation grade foam if they must be stored on top of each other. In this case any cracked plates should be placed on top of the pile. Ideally all surfaces should be cushioned with a layer of inert conservation grade foam, to prevent chipping.

Ideally open display should be avoided for historic ceramic objects. Display cases offer protection against mechanical damage, as well as buffering against environmental fluctuations, while helping to keep pieces clean. Avoiding all unnecessary handling is key to keeping ceramics safe.

Consulting a conservator

A ceramics conservator will be able to:

• Survey and assess a collection, offering advice about methods of display and storage and identifying any vulnerable parts of the collection.

• Carry out treatments on broken, cracked, previously repaired or otherwise damaged pieces.

• Advise on safe transportation and display for small museums and collectors

• Perform specialised treatments like desalination, consolidation, and bonding.

Acknowledgments: Lorna Barnes (MA)

This article offers general guidance and is not intended to be a substitute for the professional advice of an accredited conservator. The views expressed are those of the author or authors, and do not necessarily represent the views of IPCRA. IPCRA accepts no liability for any loss or damage which may arise if this guidance is followed.

Find a Conservator