What is the white haze on late-1950s Kodachrome slides, and is it safe to wipe off?
Asked 6/30/2019
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I'm scanning some Kodak slides and only the late-1950s ones have developed a white film or haze on the image/emulsion side rather than the glossy side. It wipes away easily with a clean microfiber cloth. What is this residue, and is there any risk in removing it when cleaning the slides for scanning?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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The emulsion side of Kodachrome was coated with a clear protective lacquer. Perhaps it has oxidized. Additionally, this coat may attract dust and such as it can gain an electrostatic charge. Lacquer is used to protect the Kodachrome emulsion. Lacquer is made from “guncotton”. Ordinary cotton is treated with nitric acid and solvents to make lacquer. As time goes by, its composition changes; it outgasses solvents and plasticizers. In other words it disintegrates. Lacquer is a cousin of the cellulose nitrate film base that was replaced by “safety film” in the late 1950’s. Cellulose nitrate film burns with explosive vigor. Cellulose acetate (safety film) will burn if lit by a flame, but will self-extinguish.
Originally by user44949. Source · Licensed CC BY-SA 4.0
user44949
7y ago
0
Generated from our catalog & community — verify before relying on it.
The white haze is most likely related to the protective lacquer coating used on Kodachrome slides. That coating can age, oxidize, attract dust through static, and gradually break down as it loses solvents/plasticizers over time.
If it wipes away easily, you're probably removing surface residue or degraded coating material rather than harming the image immediately. However, because this is the emulsion side, it should be cleaned very gently. Aggressive rubbing could damage the image layer even if light wiping seems safe.
So: yes, it is likely age-related coating deterioration, and careful removal of loose haze is generally reasonable for scanning, but use a very soft, clean cloth and minimal pressure.
If the slides are important, handle them cautiously because older film materials and coatings can become fragile with age.
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UniqueBot
AI7y ago
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