In ceramic sanitary ware production, many cracks, deformations, dimensional deviations and firing defects do not begin in the kiln.They often begin during drying.
The purpose of drying is not simply to remove water from the green body. It is to let moisture migrate evenly, allow the body to shrink uniformly and keep the product structurally stable before firing.
For sanitary ware factories, drying uniformity and drying cycle time directly influence first-pass yield.
A ceramic body shrinks as it changes from wet to dry. Digitalfire’s drying shrinkage reference notes that a typical plastic pottery clay may shrink about 6%, while highly plastic bodies can shrink up to about 7.5%, making drying cracks more difficult to avoid when shrinkage is not well controlled. |  |
This may later appear as warping, hidden cracks, rim deformation or unstable fired dimensions.
Faster drying does not always mean higher efficiency. Excessive temperature, low humidity or strong airflow can remove water too quickly from the surface while internal moisture remains. The product may look dry from the outside, but moisture gradients still exist inside. During handling, glazing or firing, these hidden stresses may turn into cracks or deformation.
The research review Perspectives in drying of ceramics explains that drying is a crucial ceramic processing stage, with two major concerns: it can lead to warping or cracks that damage product quality, and it requires significant energy input. This means drying is not only a quality issue, but also a cost issue.
| Many factories focus on casting output but underestimate drying capacity. If forming is fast but drying space is insufficient, green bodies wait in unstable conditions. If drying time is shortened to catch up with production, cracking, deformation and rework may increase. The result is common: output seems higher, but the yield rate falls. |  |
Drying cycle time must match forming, trimming, glazing and firing. Different products should not all use the same drying rules. One-piece toilets, large basins and wall-hung toilets require staged drying curves according to wall thickness, moisture content, structural span and support method.
Industrial sanitary ware drying systems describe flexible chamber drying technology with temperatures from 90°C to 130°C, hot air recovery and airflow systems designed to reach every part of the ware.
Factories should record green body moisture, drying temperature, humidity, airflow, drying time, product placement, support condition and defect batches. These records should be linked with first-pass yield, cracking rate and deformation rate. Following the logic of ISO 22400 manufacturing operations KPIs, drying should not only be judged by whether it is completed, but by how it affects quality, efficiency and abnormal trends.
Drying determines yield rate because it determines whether the body shrinks evenly and enters firing in a stable condition. Drying too fast creates stress. Uneven drying causes deformation. Poor cycle matching creates waiting and rework. For ceramic sanitary ware factories, stable yield rate is not achieved by final inspection alone. It is built earlier through temperature and humidity control, airflow management, proper support and synchronized drying cycle time.