Grade | Comments | Weight (g/m2) | Thickness (mm) | Flow Time*1 (sec) | Absorption speed*2 (cm) | Wet Strength *3 (kPa) | Nominal Rating (µm) | Collection Efficiency (%, 0.3µm DOP) | Conversion*4 |
Whatman | ex-Schleicher & Schuell |
No. 3 Ashless | Medium retention (5-10 µm), fast flow rate Analysis of soils, fertilizers, cement, and minerals | 113 | 0.23 | 130 | 7.5 | 12 | 5 (Medium) | 80 | 43 | 593-A |
No. 5A Ashless | Fast flow rate, retains coarse particulates and gelatinous precipitates (>10 µm). Filter hydroxides and metallic aerosols, environmental monitoring, determine silica content in steel | 97 | 0.22 | 60 | 9.5 | 10 | 7 (Coarse and gelatinous) | 75 | 41 | 589-IH |
No. 5B Ashless | Retains medium particles (5-10 µm) such as CaCO3, PbSO4, CaCO4, MnCO3, ZnCO3, ZnS, AgCl | 108 | 0.21 | 195 | 7.0 | 12 | 4 (Medium) | 90 | 40 | 589 / 6 Green |
No. 5C Ashless | Collect fine precipitates (<5 µm) such as SrSO4, BaSO4, HgCrO4, and colloidal dispersions; gravimetric analysis | 118 | 0.22 | 570 | 6.0 | 12 | 1 (Fine) | 93 | 44 | 589 / 3 Blue |
No. 6 Ashless | Retains medium-fine particulates (2-10 µm), trace and precious metals | 103 | 0.20 | 300 | 6.0 | 12 | 3 (Medium Fine) | 90 | - | 589 / 2 White |
No. 7 Ashless | Highest purity for retaining medium particles (5-10 µm), precise gravimetric analysis | 87 | 0.18 | 200 | 7.0 | 10 | 4 (Medium) | 85 | - | - |
No. 4A Hardened | High wet strength, suitable for use under high pressure, high chemical and pH resistance, retains fine crystalline precipitates (<5 µm), slow flow | 96 | 0.12 | 915 | 4.0 | 52 | 1 (Very Fine) | 90 | 50 | - |