Weight Per Gallon Density Cups

As a quality control check, errors in composition of a paint will usually be indicated by variations in the pycnometer value. In normal use in the Paint Industry, many specifications will allow a tolerance of about 0.2 pounds per gallon. Any deviation that is larger than this would make the paint suspect regarding the proper amount of ingredients in the batch. 

To check the actual capacity of your cup proceed as follows:

1. Determine the weight of a clean density cup, with its cover, in grams. As an alternative, the cup may be supplied with an accurate tare weight for use with two-pan laboratory balances. Note: Do not interchange tare weights between cups as each cup and tare weight is matched.
2. Remove cover of specific gravity cup and fill to within 1.7mm of rim with material to be tested.
3. Carefully replace cover so that the air and excess material is expelled through vent.
4. Wipe over cover to remove surplus and reweigh. By subtracting the original weight of the density cup, the weight of the contents will be found. If a tare weight was used at the start, the balance will show the weight of the contents. Clean thoroughly immediately after use.

Test Procedure

1. Weigh cleaned density cup empty and record weight
2. Temper density cup and test liquid (Refer to appropriate test standard for proper temperature)
3. Fill density cup
4. Put cover on without tilting
5. Avoid air bubbles
6. Remove overflowing liquid carefully with absorbent cloth
7. Weigh filled density cup
8. Calculate density