The terracotta panel manufacturing process converts a variable mineral raw material into repeatable fired components. Selection, body preparation, forming, controlled drying, firing, finishing and sorting all matter, but a process list alone does not prove quality. Each stage needs a defined input, measurable acceptance criteria, records and a response when results fall outside the control limits.
Define the product and control plan first
Production should begin from an approved product definition: clay body or recipe reference, profile drawing, dimensions, internal webs, finish, colour range, orientation, edge details, support zones and applicable performance criteria. Link those requirements to a traveller, batch record or equivalent traceability system so operators know which checks apply at each stage.
The project team should also identify its hold points. These may include approval of tooling, first-off extrusions, fired colour samples, full-size units, a representative mock-up and first-production pieces. A control plan should state the measurement method, sampling rate, acceptance range, responsible role and disposition of nonconforming material. “Inspect continuously” is not enough unless the result is recorded and actionable.
Control raw materials and body preparation
Raw clay varies by deposit and extraction zone, so incoming material needs an identity and acceptance route. Relevant checks may include moisture, particle distribution, chemistry or other body-specific indicators. Storage and blending can moderate variation, but elapsed time by itself does not prove homogenisation. Record source lots, stockpile or silo movements and any additives used.
Crushing, milling, screening, proportioning and mixing prepare the body for stable forming and firing. The target fineness and recipe belong to the manufacturer’s validated process; they should not be copied from a generic article. Calibrate dosing and moisture systems, control contamination, and retain sufficient records to trace a finished batch back to its prepared body.
Make forming a dimensional quality gate
For an extruded panel, vacuum level, moisture, pressure, die condition and line speed can affect the green profile. Other forming methods have their own variables. Inspect the first pieces after a start-up, tool change or material adjustment before releasing a long run. Measure the section at agreed reference points, not only the visible face.
| Forming check | Why it matters | Useful record |
|---|---|---|
| Width, depth and thickness | Controls module, weight and engagement with supports | First-off and periodic measurements by line and die |
| Webs, grooves and support zones | Affects local geometry and the intended fixing interface | Section template, gauge or dimensioned inspection |
| Straightness and twist | Influences joints, rail alignment and final flatness | Defined datum, method and green-state trend |
| Surface and edges | Identifies tears, contamination or tool marks before firing | Approved visual reference and defect classification |
| Cut length and identification | Maintains production code, orientation and later traceability | Unit or batch label linked to the traveller |
Green dimensions are not the final dimensions because drying and firing produce shrinkage. The factory must establish allowances from validated experience and confirm them on fired pieces. If the profile or body changes, previous shrinkage factors may not remain representative.
Control drying and firing as process curves
Drying removes moisture gradually to limit cracks, distortion and internal stress. The important evidence is the controlled temperature, humidity and airflow programme for the actual section, together with loading pattern and measured outcomes. A thicker or more complex profile may respond differently from a simple panel, so one standard duration should not be assumed.
Firing develops the ceramic bond and final appearance. Record kiln identification, loading position, time–temperature data and relevant atmosphere controls. Compare critical parameters with the validated operating window and segregate material affected by an excursion. Colour alone cannot confirm a correct firing cycle, and a stable curve does not waive dimensional or physical testing.
Inspect finishing, sorting and appearance
After firing and cooling, inspect units before secondary work. Cutting, grinding, drilling or edge finishing must follow approved drawings and avoid support zones unless designed. Verify final length, width, thickness, straightness, flatness, squareness, edge quality and fixing features using methods suited to the exact product.
Appearance sorting needs a representative approved range rather than one perfect unit. Review colour, gloss, texture and permissible local marks under controlled lighting, then confirm how units will be blended for the facade. Separate intentional fired variation from cracks, chips, excessive distortion or contamination. Reference photos can help operators, but retained physical standards provide stronger control.
Link testing to lots and applicable standards
The required tests depend on product classification, jurisdiction and application. Dimensional characteristics, water absorption, strength, freeze exposure, glaze behaviour or other properties may be relevant. ISO 10545-2 specifies dimensional and surface-quality methods for ceramic tiles; ASTM C67/C67M covers sampling and tests for brick and structural clay tile. Neither should be applied to a terracotta rainscreen panel without confirming scope and the project’s acceptance route.
Test specimens must represent the lot they are said to qualify. Record sampling location, body, profile, finish, size, firing batch, preparation and laboratory. State the method, edition, result and acceptance value. A certificate without specimen identity or a report for a different section is weak procurement evidence.
Release, pack and preserve traceability
Final release
Confirm required inspections, tests, quantity, approved range and nonconformance close-out before shipment.
Piece coding
Maintain orientation, elevation or zone codes where the project uses scheduled sizes or controlled colour distribution.
Packaging
Protect arrises and finished faces, respect pallet limits and make safe unloading and inspection possible.
Handover
Provide batch records, applicable reports, care instructions and suitably labelled spare units for future replacement.
Review current terracotta rainscreen panels, compare applications in the project gallery, and include factory quality information in the technical submittal rather than treating it as marketing background.