THE PERVERSE EFFECT OF ISOPROPYL ALCOHOL ON FILM CLEANING. Notes from a Film Archivist.

Edited 15:45 hours GMT+1:
This article has been updated to clarify that my caution against isopropyl alcohol refers specifically to manual cleaning of motion-picture film, particularly acetate stocks and magnetic striped prints. While some industrial cleaning systems (e.g., ultrasonic machines using anhydrous IPA with immediate drying) have used IPA successfully under controlled conditions, for archivists and collectors working by hand there are safer alternatives such as isoparaffin-based solutions with silicone.

In the world of film preservation there is an unfortunately common practice: some laboratories and telecine operators use isopropyl alcohol (IPA) to “clean” prints and camera originals.

While this chemical is useful in other fields—electronics, optics, cleaning magnetic heads—its direct application on motion picture film requires great caution. In particular, for manual cleaning and especially with films that carry magnetic sound stripes, IPA use can be damaging. The following notes come from my continuous work with motion picture film over the last fifty years:

1) Risks for cellulose triacetate

The vast majority of camera originals (negatives and reversal) and positive prints manufactured until the mid-1990s are on cellulose triacetate.
Alcohols, even in pure form (99%), can extract plasticizers from this base, leading to:

• swelling of the support,

• loss of flexibility,

• progressive brittleness.

This weakening is not the same as vinegar syndrome (which is caused by acid hydrolysis accelerated by heat and humidity), but solvent extraction can increase fragility and mechanical risk in aging acetate prints.

2) Issues also observed with polyester

Although polyester is chemically more resistant, IPA is not entirely harmless: manual cleaning with alcohol has been reported to leave surface haze or irregular marks. Moreover, it offers no lubrication benefit for projection transport.

Dirty 16 mm film

3) Potential risk to the emulsion

Repeated or prolonged exposure to alcohols can encourage the formation of micro-cracks in the emulsion, raising the risk of image instability or loss.

4) Incompatibility with magnetic soundtracks

This is where the warning is absolute: never use alcohol on striped prints.
Kodak itself has noted that alcohols can soften the emulsion or base and, in some cases, even lift the magnetic striping, leading to progressive sound loss.

Conclusion

Isopropyl alcohol may have a place in certain industrial workflows—for example, in ultrasonic cleaning machines where anhydrous IPA (≈99%) is used with immediate warm-air drying and controlled exposure of only a few seconds.

But for manual cleaning, and above all for films with magnetic sound stripes or aging acetate stock, IPA use is best avoided.

Its improper application can endanger irreplaceable materials. For routine cleaning and lubrication there are safer alternatives, such as isoparaffin-based solutions combined with technical-grade silicones, which I will discuss in upcoming installments of this series.

Cleaning using Zippo Fluid

WHERE TO BUY SUPER-8 ITEMS? I always recommend the same store Steven Spielberg and J.J. Abrams use: Pro 8mm in Hollywood. They offer service in Spanish and English. They can be found at the following link: Pro 8mm