Ceramics are generally less sensitive to extremes or fluctuations in environmental conditions than materials like paper, wood and ivory. As this applies only to objects in good condition however, it is wise to protect all ceramics by storing or displaying them in a stable environment, with temperatures in the range 15 - 25 °C and within a relative humidity range of 40 - 60 %. Limit temperature and relative humidity fluctuations to 4 °C and 5 % respectively within any 24 hour period.
Extremes, or sudden changes in temperature and relative humidity levels may cause susceptible ceramics and glazes to crack. Adhesives used for repairs may also be adversely affected. If an object has been contaminated by soluble salts, fluctuations in relative humidity may cause disruption to the clay fabric and glaze as the salts either crystallise or redissolve.
Avoid heat build-up from lighting sources. For display, place lighting outside showcases and if possible direct light onto ceramic objects by reflection rather than direct illumination.
Take care when handling ceramic materials as they are often fragile and easily broken. Observe the following guidelines when handling ceramics:
- avoid unnecessary handling;
- use clean, bare hands or disposable rubber gloves;
- check for any breakages, cracks or old repairs;
- remove any loose parts such as lids before moving;
- do not pick up objects by handles or protruding parts;
- carry only one object at a time. Place one hand underneath the base and use the other hand to support the side of the object; and
- if a quantity of objects need to be moved, use a tray lined with bubble wrap, a thick, clean towel, cottonwool or crumpled tissue paper and pad between each object.
Storage and Display
Protect ceramic objects against dust, harmful vapours and physical damage in storage. Achieve these aims by:
- storing ceramic objects in boxes, closed cupboards or on shelves that are not subject to vibration, jarring or shock;
- keeping objects clearly visible and accessible so that handling is minimised;
- using metal cabinets in preference to unsealed wooden cupboards or display cases. These latter units may emit organic acid vapours which are harmful to low-fired, unglazed ceramic objects;
- padding objects in boxes with bubble wrap or acid-free tissue paper;
- lining shelves with inert polyethylene foam sheet or acid-free paper and leaving enough space around each object for easy access; and
- not stacking objects. If stacking is unavoidable, as in the case of plates, separate objects with acid-free paper that has been cut to size and limit the height of the stack.
If using wooden or wood-based composites for storage and display, seal them appropriately (see the chapter Preventive Conservation: Agents of Decay).