CORES  

Wind archive masters on a 75 mm (3 inch) core for preference but in any case, on not less than a 50 mm (2 inch) core. When a film has lain for some time, it adopts the degree of curl to which it has been subjected. Therefore, a film, which has been wound on a very small core, will be reluctant to be straightened out. Winding on a large core avoids this. A large core is also advantageous when film is being used on any machinery, such as a printing machine, because the difference between the diameter of the reel at the start and end of the run is less, and the tension on the film can be diminished.
If a film has already been wound for a long time with a small centre and the end of the film is sharply curled, do not directly reverse this curl, as that can lead to creasing the film and, in the case of very old film, can cause the emulsion to separate from the base. Instead, wind it onto a slightly larger core, then, at intervals of a few weeks, wind it onto progressively larger centres until the film is nearly flat. Then it may be wound on a larger core in the opposite direction (i.e. emulsion out, if it was formerly emulsion in).

A 75mm and a 50mm core