What material is used to mark measurements in a homemade hydrometer?

Using a fine-tipped permanent marker to mark measurements in a homemade hydrometer is ideal due to its durability and resistance to water and fading. A permanent marker creates clear, well-defined marks that will stand the test of time when submerged in liquid, ensuring consistent and reliable readings of the hydrometer's measurements. The ink adheres well to the typically smooth surface of the hydrometer, minimizing the risk of smudging or washing away over time.

Other options may not provide the same level of reliability. For instance, pencil marks can easily be erased or smudged when wet, leading to inconsistencies in measurements. Crayon might not adhere well to surfaces submerged in water and could easily be washed off, compromising the functionality of the hydrometer. Although paint may seem like a durable option, it could create a thick layer that interferes with accurate readings and may not bond well to the material of the hydrometer. Thus, the use of a fine-tipped permanent marker is the most effective choice for ensuring precise and lasting measurement markings.