A professional who calibrates hydrometer tubes, using chemical solutions, marking device, and graduating machine. Responsibilities include:

• Mixes solutions of high, medium, and low specific gravity according to formula.
• Tests solutions, using standard hydrometer, and adjusts specific gravity of solutions.
• Places specified ballast weight into hydrometer float and seals hydrometer, using sealing compound.
• Immerses hydrometer into prepared solutions and marks levels of each solution on hydrometer tube.
• Graduates hydrometer, using engraving machine.
• Lines paper or metal scale into degrees, using drafter's pen or metal scriber, and secures scale inside hydrometer to ensure lines correspond to graduations on hydrometer.