For archival storage, the amount of retained thiosulfate should be less than how many mg per cm2?

• A. Less than 1 mg/cm2
• B. Less than 2 mg/cm2
• C. Less than 3 mg/cm2
• D. Less than 4 mg/cm2

Answer: (B)

In archival storage, controlling chemical residues from the fixer on radiographic film is essential to protect long‑term image integrity. Thiosulfate left on the film can continue to react under storage conditions, leading to issues like image fogging, color changes, and degradation of the emulsion over time. Keeping the amount of retained thiosulfate below 2 mg per square centimeter minimizes these chemical interactions, reducing the risk of future artifacts and deterioration in the archival material. This threshold balances practicality in processing with the need for durable, long‑lasting storage. Levels lower than this are safer but often not necessary in everyday practice, while higher levels increase the chance of long‑term problems.