ASTM D88 standard test method for Saybolt viscosity
6. Apparatus
6.1 Saybolt Viscometer and Bath, as shown in Fig. 1 and described in Annex A1.

6.2 Withdrawal Tube, as shown in Fig. 2.

6.3 Thermometer Support, as shown in Fig. 3.

6.4 Saybolt Viscosity Thermometers, as listed in Table 1, for reading the temperature of the sample. Each thermometer shall conform to the requirements listed in Specification E 1 for that ASTM Thermometer Number.

6.5 Bath Thermometers - Saybolt Viscosity thermometers, or any other temperature-indicating means of equivalent accuracy.

6.6 Filter Funnel, as shown in Fig. 4, equipped with interchangeable 150-µm (No. 100) and 75-µm (No. 200) wire-cloth inserts meeting the requirements of Specification E 11 with respect to the wire cloth.

6.7 Receiving Flask, as shown in Fig. 5.

6.8 Timer, graduated in tenths of a second, and accurate to within 0.1 % when tested over a 60-min interval. Electric timers are acceptable if operated on a controlled frequency circuit.

7. Sampling
7.1 Sample the material in accordance with Practices D140, D4057, or D4177, as appropriate.

8. Preparation of Apparatus
8.1 Use a Universal orifice or tip for lubricants and distillates with efflux times greater than 32 s to give the desired accuracy. Liquids with efflux times greater than 1000 s are not conveniently tested with this orifice.

8.2 Use a Furol orifice or tip for residual materials with efflux times greater than 25 s to give the desired accuracy. See also 5.3.

8.3 Clean the viscometer thoroughly with an appropriate solvent of low toxicity; then remove all solvent from the viscometer and its gallery. Clean the receiving flask in the same manner.

NOTE 2 - The plunger commonly supplied with the viscometer should never be used for cleaning; its use might damage the overflow rim and walls of the viscometer.

8.4 Set up the viscometer and bath in an area where they will not be exposed to drafts or rapid changes in air temperature, and dust or vapors that might contaminate a sample.

8.5 Place the receiving flask (Fig. 5) beneath the viscometer so that the graduation mark on the flask is from 100 to 130 mm (4 to 5 in.) below the bottom of the viscometer tube, and so that the stream of oil will just strike the neck of the flask.

8.6 Fill the bath to at least 6 mm (1/4 in.) above the overflow rim of the viscometer with an appropriate bath medium selected from Table 2.

8.7 Provide adequate stirring and thermal control for the bath so that the temperature of a test sample in the viscometer will not vary more than more or less 0.03°C (more or less 0.05°F) after reaching the selected test temperature.

8.8 Do not make viscosity measurements at temperatures below the dew point of the room's atmosphere.

8.9 For calibration and referee tests, keep the room temperature between 20 and 30°C (68 and 86°F), and record the actual temperature. However room temperatures up to 38°C (100°F) will not introduce errors in excess of 1 %.

9. Calibration and Standardization
9.1 Calibrate the Saybolt Universal viscometer at periodic intervals by measuring the efflux time at 37.8°C (100°F) of an appropriate viscosity oil standard, following the procedure given in Section 10. See Annex A2 for viscosity oil standards available.

9.2 The efflux time of the viscosity oil standard shall equal the certified Saybolt viscosity value. If the efflux time differs from the certified value by more than 0.2 %, calculate a correction factor, F, for the viscometer as follows:
F = V/t
where:
V = certified Saybolt viscosity of the standard, and
t = measured efflux time at 37.8°C (100°F), s.

NOTE 3 - If the calibration is based on a viscosity oil standard having an efflux time between 200 and 600 s, the correction factor applies to all viscosity levels at all temperatures.

9.3 Calibrate the Saybolt Furol viscometer at 50.0°C (122°F) in the same manner as above, using a viscosity oil standard having a minimum efflux time of 90 s.

9.4 Viscometers or orifices requiring corrections greater than 1.0 % shall not be used in referee testing.