The Cannon Fenske Opaque is a popular reverse flow viscometer that has two separate timing bulbs allowing a check of results in the same test. It requires a minimum bath depth of 10 inches and a sample of 12mL. Each viscometer has a permanent serial number and is supplied with a calibration certificate indicating the constant of that tube at 40°C and 100°C.
Recertification available.
| Catalog No. | Size | Viscosity Range (cSt) | Nominal Constant |
| 920-445-025 | 25 | 0.4 – 2 | 0.002 |
| 920-445-050 | 50 | 0.8 – 4 | 0.004 |
| 920-445-075 | 75 | 1.6 – 8 | 0.008 |
| 920-445-100 | 100 | 3 – 15 | 0.015 |
| 920-445-150 | 150 | 7 – 35 | 0.035 |
| 920-445-200 | 200 | 20 – 100 | 0.1 |
| 920-445-300 | 300 | 50 – 200 | 0.25 |
| 920-445-350 | 350 | 100 – 500 | 0.5 |
| 920-445-300 | 400 | 240 – 1,200 | 1.2 |
| 920-445-450 | 450 | 500 – 2,500 | 2.5 |
| 920-445-500 | 500 | 1,600 – 8,000 | 8.0 |
| 920-445-600 | 600 | 4,000 – 20,000 | 20.0 |
| 920-445-650 | 650 | 9,000 – 100,000 | 45.0 |
