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- 1). Store a container of distilled water near the liquid you wish to test. This ensures the two substances are at approximately the same temperature.
- 2). Pour water into the glass testing cylinder, until it is ¾ full.
- 3). Place the hydrometer gently into the water of the testing cylinder. As you let go of the hydrometer, give it a light twist, spinning it inside the cylinder. This will remove any air bubbles clinging to the base of the device.
- 4). Check to be sure the hydrometer is not in contact with the sides of the cylinder and is floating without restraint in the water.
- 5). Observe the curve the water forms in the container. The water levels on the sides of the cylinder are higher than the level in the center. This curve is known as the meniscus.
- 6). Note the marking of the hydrometer where it crosses the center of the meniscus, or the lowest point of the curve. Water should give a reading of 1000 specific gravity.
- 7). Adjust your measurements according to these results. For example, if your water test gave you're a reading of 1004, every reading you take that day will have to have 4 subtracted from it to be accurate. If your water test gave a result of 990, then all the remaining results for the day should have 10 added to it.
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