Drum scanning is a messy business. In this picture you can see what the mounting station looks like.
Original transparencies and negatives are taped to the surface of the drum and then covered with a sheet of clear scanning foil. Anti-newton oil or gel is placed above and below the original and then a roller is used to ensure that it coats both sides evenly.
The foil is then firmly taped around the edges to ensure that no oil escapes into the scanner mechanism when the drum is rotatating at speeds of up to 1800 rpm.
The coloured liquids are drum and film cleaner. Film cleaner is harmful to the highly polished drum surface so colourants added so that you can remember which is which.
So why do we bother with this messy process?
1. The scans are cleaner – as the oil is squeezed over the surfaces of the transparency/negative dust and debris is removed along with the excess oil.
2. Imprefections on the surface of the originals are filled in with oil and become less noticeable because this stops them refracting light as it passes the scanner sensor.
3. The image is held completely flat against the drum surface so there is no distortion, no focus problems and there are no Newton's Rings.
