Overview
ISO 7057:1981 specifies requirements for plastics laboratory ware - filter funnels used for aqueous filtration up to laboratory temperatures (nominally 0–60 °C). The standard defines preferred internal bowl diameters, general funnel geometry, construction features and marking requirements. It also includes two validation tests in annexes: an ionic extraction (conductivity) check and a flexibility (deflection) test to ensure chemical cleanliness and mechanical performance.
Key topics and technical requirements
- Scope and sizes
- Six preferred sizes are defined by the internal bowl (pavilion) diameter. Dimensions and general designs are given in a figure and a dimensional table (tolerance on diameter: +5%).
- Geometry and construction
- Bowl approximates a truncated cone coaxial with the stem.
- Internal surface is ribbed; the exterior of bowl and stem must have at least three external ribs regularly spaced. A rim is required for rigidity.
- The bowl wall slope is about 60° from the axis (design detail shown in the standard).
- Stem end is rounded; stem length proportions are specified:
- For funnels ≤100 mm bowl diameter: stem length 75–100% of bowl diameter.
- For funnels >100 mm: stem length 60–80% of bowl diameter.
- Internal surface must have a continuous, regular contour from bowl to stem; wall thickness and edge shape must allow the flexibility requirement.
- Materials
- Funnels must be made from rigid, non‑brittle plastics with suitable chemical and thermal properties and free of molding defects and stresses. Markings must include material name/symbol and maximum recommended temporary use temperature (example given: “PP 135 °C” as an inscription style).
- Marking
- Permanent, legible markings required: manufacturer/vendor name or mark, material (or symbol), recommended maximum temporary temperature, funnel size (where specified), and the ISO number.
- Performance tests (Annexes)
- Annex A - Resistance to extraction of ionic material by water at 60 °C: after specified rinsing and extraction, the aqueous extract’s increase in conductivity must not exceed the value stated in the standard (document notes this limit as 200 pS/m and equates it to roughly 1 mg/L NaCl).
- Annex B - Flexibility test: with the stem blocked and funnel filled with ~200 mm of water at 60 °C, a 1 kg weight is hung from a marked rim point; the external bowl diameter increase at that point must not exceed 5%.
Applications and who uses it
- Laboratory equipment manufacturers and molders designing and producing plastic filter funnels.
- Quality assurance and inspection teams performing incoming or production testing.
- Procurement specialists and laboratory managers specifying compliant funnels for chemical and analytical labs.
- Regulatory and standards professionals harmonizing lab-ware specifications.
Related standards
- ISO 4798 (glass laboratory funnels - referenced for alignment of specifications)
- ISO 1043 (plastics - symbols and abbreviations for material marking)
Keywords: ISO 7057, plastics laboratory ware, filter funnels, plastic funnels, filter funnel dimensions, ionic extraction test, flexibility test, laboratory plastics, funnel marking, QA testing.
