EN 12875 Dishwashing Resistance Testing: Test Cycles

# EN 12875 Dishwashing Resistance Testing: Test Cycles

EN 12875 specifies a mechanical dishwashing test that measures how well materials, coatings, and finished articles resist repeated machine washing. It evaluates tableware, hollowware, cutlery, and decorative surfaces under simulated domestic or commercial conditions. Test cycles combine thermal, chemical, and mechanical stresses in a controlled, repeatable sequence.

Principle & mechanism

Dishwashing resistance testing reproduces the combined attack an article experiences in service: hot alkaline detergent, spray-arm impact forces, thermal shock at rinse stage, and drying heat. Several mechanisms degrade the material together. Alkaline surfactants and phosphonate or carbonate builders soften or swell organic coatings. They also attack glass surfaces through ion exchange. Mechanical jet impingement erodes weakly adherent layers and exposes fresh material to chemical action. Thermal cycling between wash, rinse, and drying phases creates repeated stress at coating-substrate interfaces. This initiates micro-cracking and edge corrosion on plated or lacquered metals. Single-factor tests such as Damp Heat Resistance Testing apply steady humidity alone. The dishwashing cycle instead superimposes all stress factors in a defined, repeatable sequence. This is why the method discriminates well between surface treatments that appear equivalent under visual inspection.

Test principle and cycle parameters

EN 12875 defines complete washing cycles run in a reference dishwashing machine. Cycle parameters are fixed so that different laboratories reproduce comparable stress. Each cycle has a wash phase with detergent dosed into a defined water volume, one or more rinse phases, and a drying phase. A defined pause follows before the next cycle begins. Water temperature, detergent concentration, water hardness, and cycle duration are fixed for domestic and commercial severity levels. The detergent composition is standardized because surfactant and builder content strongly influences corrosivity. Water hardness is adjusted with calcium and magnesium salts. Hard water accelerates spotting and filming on glass and metallic surfaces. Specimens undergo a specified number of cycles, commonly selected in stepped series such as 56 cycles. Performance can then be ranked at intermediate inspection points rather than only at completion. Between inspections, specimens cool and dry under standardized ambient conditions.

Sample preparation and loading

Specimens are prepared as finished articles or as coated test panels representative of production surfaces. They must be free of grease, fingerprints, and packaging residues, since contamination alters wetting and chemical attack. Each specimen receives an identification mark on a non-critical area using a method resistant to washing. Edges and cut faces of metallic panels may be protected, for example with a resistant lacquer. This prevents edge corrosion from masking evaluation of the functional surface. Any protection must be recorded in the report. Loading follows the machine geometry defined by the standard. Specimens are secured on racks in designated positions where spray intensity is characterized. Functional surfaces are inclined toward the jets, without mutual shielding. Reference plates with known sensitivity are included in each run. They verify that the machine and detergent regime stay within control limits. Overloading the rack, as in a typical household machine, reduces jet impact and invalidates the comparison between runs.

Test procedure and equipment

The core equipment is a reference dishwashing machine of the type specified in the standard. It is fitted with conductivity or flow monitoring to confirm correct water exchange, plus water-conditioning and dosing apparatus for detergent and hardness salts. Before the run, the operator verifies calibration of temperature sensors and dosing pumps. The operator prepares the detergent solution at the specified concentration and records water hardness. Specimens and reference plates are loaded, the cycle programme is selected, and the machine runs the specified number of cycles without manual intervention. After the final cycle, specimens are removed promptly. They are rinsed in clean water where the standard requires it and dried in air at room temperature without wiping. Wiping could remove loosely adherent corrosion products relevant to grading. Visual examination follows after a defined recovery period. As with any durability programme, for example EN 892 Climbing Rope Testing: Impact Force, Fall Rating and Dynamic Performance, traceable documentation of machine settings and consumable batches underpins result comparability between laboratories.

Result evaluation and grading

Evaluation is performed by trained inspectors under controlled illumination. Each specimen is compared against unexposed retain samples and, where applicable, against limit samples agreed between parties. The standard defines rating levels describing the type and extent of change. These cover corrosion or tarnish on metallic surfaces; blistering, cracking, flaking, or loss of adhesion of coatings; marking and staining; and surface dulling or iridescence on glass and glazed articles. Changes are graded by extent and severity and photographed for the report. Edge effects and areas near identification marks are assessed separately from the functional surface. Disagreement cases are resolved with optical magnification, since fine stress-corrosion patterns on silver-plated items are not resolvable to the unaided eye. The report states the number of cycles completed, the severity level applied, ratings for each specimen, and observations on reference plates. Purchasers can use it to set acceptance limits, such as a minimum rating after a stated cycle count.

Application to materials and coatings

The method applies to a broad range of dishwasher-declared products: stainless steel and silver-plated cutlery, aluminium and anodized hollowware, ceramic and glass tableware, enamelled ware, and organic coated or lacquered articles. These include decorated glass and painted metal surfaces. The critical failure mode differs for each material class, and EN 12875 grading accommodates this range within one framework. Tableware suppliers use the test for product development and batch control. Retailers reference it in purchasing specifications. Accredited laboratories apply it for market-surveillance verification of dishwasher-suitability claims. The method complements other environmental resistance tests in a durability programme. Damp-heat or corrosion exposure covers climatic stress, while dishwashing cycles address combined chemical-mechanical-thermal service load. When a product must also withstand transport or installation abuse, dishwashing resistance may be combined with mechanical tests analogous to Stone Chip Resistance Testing: Key Test Items and Checks. This characterizes both surface chemistry tolerance and impact durability.