Kiln loading affects sanitary ware deformation because ceramic bodies shrink and become less resistant to deformation at high temperature. Product orientation, support position and contact conditions redistribute gravity and internal stress.
· The same product fired with the same body and temperature curve may deform differently when placed horizontally, vertically or on different supports.
· Correct loading is therefore not simply about keeping the product stable.
· It must provide sufficient high-temperature support while allowing controlled firing shrinkage.
Sanitary ware kiln loading is the process of positioning glazed toilets, basins, wall-hung products and other ceramic bodies on kiln-car plates, kiln furniture or dedicated setters before firing. A loading standard normally defines product orientation, support points, contact area, spacing, kiln-car level and treatment of the supporting surface. |  |
1. Orientation changes the gravitational bending moment
As a ceramic body approaches vitrification, it becomes more vulnerable to high-temperature deformation. Digitalfire’s warping reference explains that vitreous bodies can soften during firing and that overhanging or structurally unstable sections may sag.
A large basin fired horizontally may bend across its bottom span. When placed on its side, the rim or mounting surface may become the main load-bearing area. Orientation should therefore be selected according to the product’s center of gravity, unsupported span and wall-thickness distribution.
2. Support points determine stress concentration
Too few support points allow unsupported sections to sag. Too many supports, or supports with unequal heights, may restrict normal shrinkage and create local pressure or twisting.
The study Ceramic Sanitary Wares: Prediction of the Deformed Shape After the Production Process used numerical modelling to predict sanitary ware deformation, demonstrating the need to consider geometry, material shrinkage and mechanical boundary conditions together.
3. Contact surfaces control shrinkage freedom
During firing, the product shrinks in length, width and height. Excessive friction or local sticking between the body and firing plate can prevent free movement, causing different areas to shrink at different rates.
automated kiln loading includes the positioning of ceramic support plates and protective materials in its automated kiln-loading process. These supports are used to reduce damage associated with firing shrinkage.
4. Kiln-car position adds thermal variation
Products placed near kiln-car edges, lower levels or concentrated heat-flow areas may experience different heating conditions. When product orientation combines with temperature variation, local shrinkage differences can become more severe.
A loading plan should therefore be validated together with kiln temperature distribution, product spacing and loading density.
Check the center of gravity: Avoid unsupported large spans.
Standardize orientation: Use a fixed position for each product model.
Optimize supports: Support stable areas and avoid point pressure.
Allow shrinkage: Reduce friction, sticking and excessive restraint.
Control spacing: Maintain airflow and temperature uniformity.
Build traceability: Record kiln-car position, support method and deformation direction.
Kiln loading affects deformation because it changes the stress path during high-temperature softening and firing shrinkage. Orientation determines gravitational loading. Support points determine stress concentration. Contact surfaces determine shrinkage freedom. High-quality kiln loading is not about placing the maximum number of products on a car. It is about allowing every product to complete firing in a controlled and repeatable position.
Q1: Why can the same firing curve produce different deformation on different kiln cars?
A: In addition to temperature variation, differences in product orientation, support height, contact area and loading density can change firing stress and shrinkage.
Q2: Are more support points always better?
A: No. Too few supports cause sagging, while too many or uneven supports restrict shrinkage. Supports should be placed under structurally stable areas without creating local pressure.
Q3: How can a factory verify a kiln-loading method?
A: Compare different orientations and support arrangements through controlled firing trials, then record mounting-surface, rim and dimensional changes to create a standard loading diagram for each model.