With a mere snap of his fingers, Thanos reduced half of the Marvel Cinematic Universe to so much dust in the wind. But achieving the cataclysmic Snapture that closes out this summer’s all-star blockbuster Avengers: Infinity War wasn’t as simple as the mad Titan makes it look.

Infinity War‘s special effects supervisor Dan DeLeeuw tells Yahoo Entertainment that his team did a number of passes to make sure the heroes’ ashes would scatter just right. “It was definitely a process figuring out what the ash would be,” he says, noting that the first version of the Snapture drew on the power of all the Infinity Stones embedded in Thanos’s appropriately named Infinity Gauntlet. “We had always paid special attention to what the stones could do. For example, when Thanos uses the Space Stone to immobilize someone, there’s always this blue effect that’s around it. So we tried to use that same kind of rule for the end: If you break up a human, what are you breaking up?”

View photos Thor (Chris Hemsworth) looks on helplessly as Thanos executes the Snap. (Image: Marvel Studios) More

As DeLeeuw explains it, a hero like Tom Holland’s Spider-Man would break apart as follows: First the Soul Stone would disintegrate his soul, then the Power Stone would take care of the body, and the Space Stone would scatter those particles around. It was a mesmerizing effect — too mesmerizing, it turned out, for the film. “It stepped on every wonderful thing that the actors were doing,” DeLeeuw recalls. “We realized it had to become about less being more.”

So instead of incorporating all the stones, the F/X crew reconceived the Snapture so that each disappearance appears to be caused by the Power Stone specifically. “We were kind of leaving their corporeal form behind, and erasing them from the universe. It became less about the effect of the stones and more about what ways we can depict each person disappearing. Some people can hold on longer and some people go fast; that became something that fans have theories about. People have different theories about why Peter could last so long and someone like Drax went quickly.”

Irrespective of fan theories, there’s a practical reason why Holland took the longest to disappear. His abrupt farewell to his mentor, Tony Stark, is arguably the movie’s emotional high point, and that made it the perfect death for the F/X team to use as their test run as they perfected the vanishing effect.

View photos Peter Parker (Tom Holland) doesn’t feel so good as he succumbs to the Snapture in Infinity War. (Image: Marvel Studios) More

“It’s the most pulling-at-the-heartstrings moment we had, and it was the one you were going to study the most because of how long it took for him to actually disappear,” DeLeeuw says. “We art-directed it around his performance; when he says, ‘I don’t feel so good,’ you want to make him start to go, and his hands go first, but you can’t do his face yet, because you gotta keep it for when he falls to the ground and Tony catches him.” Holland famously improvised his death scene, and, according to DeLeeuw, he did so without knowing what the finished effect would look like. “The mystery of what it would be might have helped their performance. Because their characters didn’t really understand what was happening either.”

So that’s the Snapture explained for you, but Infinity War contains a number of other scenes that are worthy of further study now that the film is on Blu-ray. We asked DeLeeuw and production designer Charles Wood to share some of their favorite secrets behind the film.

Watch the complete history of the Marvel Cinematic Universe from the dawn of time to the Snapture: