How to Tell Earthenware, Stoneware and Porcelain Apart
Earthenware, stoneware and porcelain are all fired clay ceramics, but differences in raw materials and firing create distinct bodies. Identification is easiest when several features agree; colour or decoration alone is rarely enough.
Earthenware
Earthenware is generally fired at lower temperatures than stoneware or porcelain. Its body is often porous unless sealed by glaze. Exposed fabric at a foot rim or chip may be cream, buff, red, brown or grey.
Common clues include:
- A relatively soft or porous body
- A clearly separate glaze layer
- Opaque walls
- A duller sound when lightly tapped, though tapping valuable objects is not recommended
- Crazing or staining in some lead-glazed wares
Tin-glazed earthenware has an opaque white glaze over a coloured body and includes traditions described as Delftware, faience and maiolica. Names can refer to regional techniques and styles, so use them carefully.
Stoneware
Stoneware is fired high enough to produce a dense, usually non-porous body. It may be grey, buff, brown or off-white. Salt glaze can produce a thin, dimpled "orange-peel" surface, while other stonewares use ash or applied glazes.
Stoneware is usually harder than earthenware, but thickness, shape and condition influence weight and sound.
Porcelain
True porcelain is high-fired, white and vitrified, with a body and glaze that may appear closely fused. Thin areas can be translucent when held safely in front of a cool light source. Do not use hot lamps or press fragile pieces against light fittings.
European soft-paste porcelain and bone china can complicate simple rules. Body colour, translucency and glaze should be compared with known examples from the suspected factory and date.
The [Canadian Conservation Institute's ceramic guidance](https://www.canada.ca/en/conservation-institute/services/preventive-conservation/guidelines-collections/ceramics-glass-preventive-conservation.html) explains how firing temperature affects porosity and hardness and describes common glaze systems.
Inspect safely
Support the object from beneath with both hands. Never lift it by a handle, spout or finial. Examine the unglazed foot, existing chips, glaze edge and transmitted light without scratching or making a new test mark.
Do not use acid, hot needles, knives or destructive tests. Dirt, restoration and later overpainting can disguise the body.
Marks are supporting evidence
Factory marks can help, but marks were copied, reused and sometimes added later. Compare mark technique, body, glaze, shape, decoration and documented factory examples. An apparently correct mark cannot compensate for incompatible materials or construction.
Condition clues
Crazing, staining and old staple repairs occur often on earthenware, but can appear elsewhere. Porcelain can be extremely brittle despite its hard body. Restored breaks and overpaint may conceal the fabric needed for identification.
For a valuable or disputed object, consult a ceramics specialist or conservator and record all uncertainty.
For close-up examinations, restoration work and workshop discoveries, [watch and subscribe to Antique Repair Shop on YouTube](https://www.youtube.com/@AntiqueRepairShop).
Sources and further reading
- [Canadian Conservation Institute: Caring for ceramic and glass objects](https://www.canada.ca/en/conservation-institute/services/preventive-conservation/guidelines-collections/ceramics-glass-preventive-conservation.html)
- [Canadian Conservation Institute: Care of ceramics and glass](https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/canadian-conservation-institute-notes/care-ceramics-glass.html)