I saw behind-the-scenes of a 4K movie restoration — and it's made me appreciate the quality of my 4K Blu-rays more than ever now…

4K Blu-ray is a big part of my work at TechRadar. Not only is it my staple source for testing the best TVs and best soundbars , but thanks to its superior picture and audio quality over 4K streaming, the movies themselves have now become one of my main areas of coverage.

As a big fan of 4K Blu-ray, both as a user in AV testing and as a collector, I helped start our Blu-ray Bounty series, where we review the latest 4K releases from each month, scrutinizing their picture and audio quality, back in 2024.

While the 4K Blu-ray market (and the market for physical media in general) has been a volatile one in recent years, the Blu-ray fan base has always been a passionate one. As I’ve been testing more 4K releases, I’ve come to appreciate what the format can do for older titles and general at-home watching even more, and I now include myself in that passionate fanbase.

So, when I was invited to visit Silversalt Restorations, a company whose work ranges from audio restoration, data archiving and restoration and transfer of movies to Blu-ray restoration (including 4K), I jumped at the chance. The company has some big-name clients, having worked with Hammer, Arrow Video, Disney, Paramount, Universal and Criterion, among others. All of those brand’s 4Ks have been featured in Blu-ray Bounty, so I was excited to see how the magic happens.

A meticulous process

Each film is inspected frame-by-frame for marks, scratches and other imperfections (Image credit: Future)

Silversalt Restorations was founded in 2017 by a team of restoration artists, before being acquired in 2024 by John Gore Studios, another company dedicated to the preservation and restoration of classic titles, especially British cinema. Some of Silversalt’s biggest projects include The Deer Hunter , The Wicker Man , The Dollars Trilogy , The Curse of Frankenstein and the upcoming release of Dracula (the iconic Hammer horror classic starring Christopher Lee and Peter Cushing).

I was taken on a tour of Silversalt’s studio in Hammersmith, led by Managing Director Mark Bonnici, during which I was shown everything that goes into the meticulous process of restoring a movie.

My journey begins at the film inspection table, where Marie Fieldman, Silversalt’s resident film inspector, is hard at work inspecting an old film reel for damage, including visible scratches, marks, wear and tear, degradation, and even mould on each individual frame, before crafting a detailed report for the respective client. “Some of these haven’t been looked at by a human for a very long time,” Fieldman says, as she shows me an older report she did for 1954’s Men of Sherwood Forest . Here, she’s labelled every single defect she can find, noting the level of damage and the best course of action.

Once the film reel is ready, it's then put through the cleaning machine (pictured) (Image credit: Future)

She tells me about what fixes can be implemented, such as the cleaning of mould and even using a blank frame in place of a damaged one, which won’t be noticeable in the final movie, noting that deep scratches can be particularly problematic.

Once she is happy with the state of the film reel, it’s taken over to a cleaning machine. The reel is mounted and travels between Dacron rollers where surface dirt is gently removed with a film-safe solvent. Marie warns, “In some cases the film may need to be hand cleaned, for example if the film has a wax coating”. Once the film is clean, it’s ready for scanning.

Scanning

The Arriscan XT (pictured) can scan up to 6K resolution files Future

The Laser Graphics Director (pictured) can scan up to a staggering 13.5K resolution Future

Next, Bonnici shows us the two scanning machines Silversalt uses. The first is the Arriscan XT. The Arriscan XT can use a wet-gate system, where the film is immersed in a Kodika, a special liquid which optically minimises scratches and marks as the film is digitised into a digital image sequence, known as a DPX file. The film is scanned in at 6K resolution, before being downgraded to 4K for 4K Blu-ray. “The Arriscan XT was originally designed for new film stock, but was later revised to handle archive/legacy film too,” Bonnici says.

He then shows us a more advanced film scanner, the Laser Graphics Director scanner. This scanner is specifically designed for archival footage which also uses an infrared light to detect marks and scratches on colour film and makes corrections during the scanning process. The Director scans up to 13.5K resolution and can handle 8mm to 35mm film.

Restoration

It takes a lot of hard work to get an old film ready for 4K Blu-ray (Hammer Films' 36 Hours pictured) (Image credit: Hammer / Future )

Once cleaning and scanning are completed, the DPX files are sent to the restoration artists, who work their magic to restore the uploaded film reel by correcting image instability, removing superfluous scratches and marks that the scanner has picked up from the original film, removing excess film grain, and generally tidying up the image.

The digitised frames are saved to file storage and then the digital restoration work begins. The frames are analysed for film dirt and the results are presented to the restoration artists, they can review these in a red mode, which highlights the differences between the results and the original version and any falsely removed part of the image reinstated. “We spend most of our time putting detail back in that’s been incorrectly removed,” restoration artist Anthony Badger tells me. “The system can sometimes struggle to distinguish between dirt and other textures within the film, like snow.”The artists perform other tasks such as stabilisation, deflicker, scratch removal etc. Anthony shows us various examples of larger fixes performed by the artists.

One of the clips I’m shown shows the red filter picking up what it thinks are marks and scratches. However, it also highlights a section of a character’s trouser leg and attempts to remove it, mistaki...

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