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Frequently Asked Questions

Measuring Specific Gravity of Process E-6 Solutions

How do I measure specific gravity of Process E-6 solutions?
You can make specific-gravity measurements of your solutions with any hydrometer that meets the standard ANSI/ASTM E100-72. The hydrometer should be marked in increments of at least 0.001 for an accuracy of plus or minus 0.0005. Although most hydrometers are calibrated at 15.6 degrees Celsius (60 degrees Fahrenheit), they are useful at other temperatures. To measure the specific gravity of Process E-6 solutions, you will need the standard hydrometer listed below.

Table 1: Hydrometers for Process E-6 Solutions
Solution Range of Standard Hydrometer ASTM Number
First Developer and Replenisher 1.050 to 1.100 126H
  • Reversal Bath and Replenisher
  • Color Developer and Replenisher
  • Pre-Bleach
  • Pre-Bleach II and Replenisher
 1.000 to 1.050 125H
Bleach* and Replenisher
  • 1.100 to 1.150
  • 1.150 to 1.200
  • 1.200 to 1.250
  • 1.250 to 1.300
  • 127H
  • 128H
  • 129H
  • 130H
Fixer* and Replenisher
  • 1.000 to 1.050
  • 1.050 to 1.100
  • 125H
  • 126H

* More than one hydrometer is listed for bleach and fixer because the acceptable ranges of the specific-gravity measurements for these solutions are too large.

Note: You should not need all six standard hydrometers listed in the above table for any one type of machine running Process E-6.

Take these steps to measure specific gravity:

  1. Fill a clean, dry 250 mL graduated cylinder to within 2.5 cm (1 inch) of the top with the solution you are measuring.
  2. Adjust the solution to the proper temperature. Proper solution temperature is very important.
  3. Place the cylinder in a sink or tray to catch overflow.
  4. Choose the correct hydrometer to match the approximate specific gravity of the solution.
  5. Be sure that the hydrometer is clean and dry. Carefully lower the hydrometer into the solution. Let it bob up and down slightly. When it stops, read the number at the top of the meniscus. (See Figure 1.)
  6. After making the measurement, discard the sample. To avoid contaminating the solutions, do not return the sample to the tank.
  7. Rinse the hydrometer and graduated cylinder thoroughly with water.

[meniscus.gif]

Figure 1

Notes:

  • Never take specific-gravity readings of solutions in the tanks.
  • If you use the wrong hydrometer, it can sink to the bottom of the tank and break, or bob to the surface where the stem may hit the edge of the tank and break.
  • Label hydrometer boxes to avoid confusion.
  • Do not use tape labels on the hydrometers.


FAQ5011