The design work for these characters can be traced back to Ralph McQuarrie's early drawings and paintings produced in 1975 as part of George Lucas' wish to help visualise the movie for Fox company execs..
Moving on a year or so to February 1976 as pre-production started in London, an original clay sculpt was produced of the Stormtrooper helmet (by Liz Moore) and armour (by Brian Muir) which was then moulded by plasterers, refined by Brian Muir, moulded and then casted for production. As you can see at this stage in the design process the sculptor was by now very close to nailing the finished screen look. - especially when you look at the curves around the frown and nose sections.
The physical manufacturing (vacuumforming
) of the helmets and armor were the responsibility of Andrew Ainsworth (AA) at Shepperton Design Studios in Twickenham, established a few years earlier in 1974. Ainsworth and SDS became a key element in the production process given their manufacturing input into a significant number of helmets and costuming parts for the movie including the Stormtrooper, TIE Pilot, Death Star Gunner, Imperial Guard, Rebel X and Y-Wing pilots, Rebel Fleet Trooper and Rebel Ground Crew/Guards.
Here a shot of some partially completed helmets and armor outside Shepperton Design Studio's near London in March 1976. As you can see the helmets have all been spray-painted, and many have the ears and brow trims attached. If you look closely the "mic tips" look more bulbous and less defined than the screen-used ones suggesting that they were replaced by the Art department at the Studio. Behind them you can see some vac-formed sheets of armor, ready to go to the Studio where John Mollo's team assembled the costumes.
SDS's original receipts dating back to 1976 show that in total they fabricated fifty-six Stormtrooper helmets, twelve Imperial Forces' (Gunner) helmets, twelve Imperial (TIE) Fighter Pilots' helmets and twenty X-Wing Fighter Pilots' helmets - along with the Imperial Guards and of course the Stormtrooper and TIE Armour.
Ainsworth was initially approached to produce around 50 Stormtrooper helmets. However, as soon as he began he realised that the complex shape of their design (such as the male and female curves on the helmet rear) WE THINK
he used a less than ideal kind of plastic, High Density Poly Ethylene. HDPE is a flexible material now used to make things like milk cartons, but the khaki-green coloured sheets (TWO diferent colours were used) Ainsworth used required him to spray-paint them white. So fifty of these "Stunt" helmets were produced and the vast majority of Stormtroopers you see in the movie are them.
However, because painted helmets don't look all that great under close scrutiny, Lucasfilm/Mollo requested that Ainsworth also produce six "close up" helmets when Stormtrooper were to be featured more prominently - such as when Luke and Han are disguised as Stormtroopers (although they can also be seen in numerous other shots as well). We refer to these six as the "Hero" Stormtrooper helmets as they were made to a higher specification, vac-formed in a shiny white ABS plastic, and have a higher quality of detailing, including curved eye lenses. Hence in the screen-shot below the Hero is on the Left, with the Stunt on the Right. Note that the armor is the same, only the helmets varied.
The Empire Strikes Back - For the sequel, Mollo and his team simply re-used the same Stormtrooper costumes and helmets that had previously been used in A New Hope. This was the simplest solution since less than a dozen were required - and it also saved them money on what was a strict budget. For Return of the Jedi over 50 were needed so new armor and helmets were produced - cast from an original ANH set.