Crossover Procedure When Changing Control Strip Batches

When a roll of control strips (pre-exposed or PCE) is running out, a new roll must replace it. Because the emulsion of the new batch may give different densities, a crossover is essential; otherwise the processor may be adjusted incorrectly and film produced with low or high density.

Highlights

1. Using the current control strips, confirm that the processor is in control and meets current aims, and correct it if necessary
2. Splice three strips from the current batch and three strips from the new batch together and process them
3. Measure the RD density of the pre-exposed strip or the aim step of the sensitometer exposure for the old and new strips
4. Confirm that the old batch is within the allowed range
5. Use the new RD or aim step value as the new control aim
6. Repeat steps 1 to 4 for each processor
7. Record the crossover and new densities on the process control chart or start a new chart for each processor

For more information, refer to D-17 Control Procedures for Source Document Microfilm Processing.