Pearlescent or iridescent glaze is a viewing-condition finish: the accepted appearance must be defined by physical samples, light, angle, distance, orientation and a documented range.
This guide turns an old product launch into a practical selection workflow for architects and facade teams. It covers the base colour and finish record, batch control, edges and cuts, cleaning trials, durability evidence, module and joints, and coordination with the complete rainscreen assembly.
Start with a complete finish identity
Before comparing samples, request the current manufacturer, item code, clay body, base or engobe colour if used, glaze/finish name, declared production sequence, profile, work size, thickness, mass, tolerances, permitted orientations and intended exterior application. Record which facts are manufacturer declarations and which are project requirements.
The 2020 post calls titanium dioxide the main component and links it to the “magic colour” effect, but provides no formulation, supplier data or test report. That composition claim is not carried forward. A current technical data sheet should identify the relevant finish system without asking the design team to infer chemistry from marketing copy.
Review the colour under controlled light and angles
Iridescent appearance can shift as the viewer, panel and light move relative to each other. Build a sample plan that includes the project’s important approach directions, facade orientations, likely viewing distances and both the intended daylight and artificial-light conditions. Keep the sample orientation marked; rotating the same piece may change the result.
Base and face colour
Record the clay/body or base colour, visible face colour and any surface texture. Confirm whether edges, reveals and cut faces expose a different layer or tone.
Angle sequence
Review each sample face-on and obliquely from planned routes. Note when the colour shift appears, disappears or becomes uneven rather than calling one photograph the standard.
Light sequence
Compare representative daylight and specified artificial sources in the intended orientation. Record source, position and observation conditions so approvals can be repeated.
Distance sequence
Check a hand sample for surface character, a full panel for uniformity and joints, and a multi-panel mock-up for elevation-scale distribution.
Define batch range, distribution and acceptance
Approve a signed master sample together with a representative range, not one ideal chip. Establish how production batches will be identified, compared, blended across elevations and held for replacements. Mark samples with item, finish, batch, face direction and date; photograph them only as a supplementary record because cameras, displays and editing can alter iridescence.
Use a multi-panel sample to review transitions between units. Decide whether the design seeks a calm field, a controlled shimmer or an intentionally varied mosaic. Set acceptance criteria for colour distribution, gloss, surface marks, edge appearance and visible differences at the agreed viewpoints. A broad phrase such as “rainbow-like” is design intent, not a measurable acceptance criterion.
Coordinate edges, cuts, module and joints
Ask the manufacturer which faces and edges receive the declared finish, which panel orientations are permitted, and whether special lengths, returns or factory-finished pieces are available. Determine what happens visually and technically at factory or site cuts, drilled or machined areas, corners, openings and replacement pieces. Do not assume that a face glaze continues around every edge or that an exposed cut can be repaired invisibly.
Lay out the facade using actual work sizes, tolerances and support zones. Joint width, depth, backing colour and shadow can strengthen or interrupt the pearlescent field. Coordinate courses with sills, heads, corners, parapets, bases and adjacent glass/metal/stone; confirm how movement and installation tolerances are absorbed without creating unintended colour bands or misaligned reflections.
- current item/profile and retained production-range samples with labelled orientation and batches;
- multiple full panels, actual joints/backing, a corner or return, opening edge and typical cut/special piece;
- selected rails/clips/anchors or other support route, cavity, insulation, membranes, drainage and fire interfaces;
- daylight and specified artificial-light reviews from agreed near, middle and distant viewpoints;
- approved cleaning trial, touch/replacement strategy and recorded acceptance decisions; and
- clear separation between visual approval and structural, water, fire or durability tests.
Request evidence for exposure and cleaning
| Question | Request | Do not assume |
|---|---|---|
| Colour and gloss retention | Applicable weathering and UV/light-exposure method, exact finish/item/batch, exposure conditions, measured criteria and limitations | “Non-fading,” a white base or pearlescent pigment guarantees permanent appearance |
| Water absorption | Current standard, sampling, exact clay body/profile/finish and declared result | A glazed face establishes whole-unit absorption or wall watertightness |
| Freeze-thaw suitability | Applicable climate/jurisdiction, exact-product test method/cycles/acceptance and project exposure assessment | Glaze, firing language or a generic terracotta result transfers to every profile |
| Surface/edge durability | Relevant abrasion, impact, adhesion/crazing or other finish evidence required by the project, including cut-edge limits | “Double-layer” proves greater strength, thickness or resistance |
| Cleaning and maintenance | Manufacturer/project O&M guidance, contaminant identification, compatible product/method, inconspicuous trial and approved mock-up | Acid, alkali, solvent, abrasive, pressure or sealer is safe without review |
Start cleaning evaluation with the least aggressive compatible option and protect joints, metals, seals, membranes and adjacent finishes. Record chemical/product, concentration, tools, dwell/rinse conditions and results for the approved trial; the article deliberately supplies no universal recipe. Investigate staining or colour change before cleaning so the method does not mask a drainage, sealant, corrosion or runoff problem.
Coordinate the complete facade system
The glazed face is one component. Assign responsibility for panel strength and edge zones, rails/clips/anchors, bracket/substrate capacity, tolerances, wind and other applicable actions, cavity, insulation, membranes, flashings, drainage, fire barriers, openings and interfaces. Confirm corrosion compatibility and safe panel replacement. Fired clay and glaze do not by themselves establish whole-wall fire, water, thermal or structural performance.
For current options, review the dedicated Pearlescent Terracotta Cladding page and the broader Terracotta Rainscreen guide, then request current item-specific drawings, declarations, samples, test reports and system information through Contact.
Prepare a pearlescent glaze sample brief
Share the building and exposure, desired base/shift colours, panel profile and module, facade orientations, viewing routes, daylight/artificial lighting, edges and special pieces, joint/backing concept, system route, evidence requirements, mock-up scope, quantity and programme.