How to clean mildew from 35mm slides

If you haven't sifted through that old box of 35mm slides in a while you might find mould or mildew encroaching on your memories. When kept in humid basements or moist garages, 35mm slides easily succumb to mildew growth -- one of the most common elements to damage slide film. Although you can clean mildew from 35mm slides, don't expect the slides to return to their original quality. Most cleaning methods will remove current mildew growth, but still leave behind areas of permanent damage on the slides.

View each slide under bright, direct lamp light to look for mildew, dust and dirt. Check both the emulsion and the glossy sides of the slide.

Aim the nozzle of a can of compressed air 6- to 8-inches away from the slide, slightly at an angle to the large pieces of debris. Spray three or four short bursts of air at the mildew to loosen and remove it.

Moisten a foam-tip medical swab by dipping it in distilled water or isopropyl-based photographic emulsion cleaning fluid.

Rub both sides of the 35mm slide with the wet swab using a circular motion and a gentle touch to carefully loosen any residual mildew. Use a new swab for each slide to reduce the transfer of mildew from one slide to the next.

Lay the slides on a clean, microfiber cloth to dry. Turn each slide over after 15 minutes of drying so both sides can air dry.

Repeat the cleaning method again for stubborn mildew growth. Store the clean slides in a protective slide case with a packet of desiccant.


Store 35mm slides in climate and humidity regulated areas, such as your home, office or bank safe deposit box.


After cleaning a 35mm slide, permanent mildew damage may appear as blistering or as a smudge that has removed part of the slide image.

Things You'll Need

  • Bright table lamp
  • Compressed air
  • Foam-tip medical swabs
  • Distilled water
  • Emulsion cleaning fluid
  • Microfiber cloth
  • Slide case
  • Desiccant packet
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About the Author

Angela Tague writes marketing content and journalistic pieces for major brands including Bounty, The Nest, Lowe's Home Improvement and Hidden Valley. She also provides feature content to newspapers and writes health and beauty blogs for Daily Glow, Everyday Health and Walgreens. Tague graduated from the University of Iowa with a bachelor's degree in journalism and mass communications in 1999.