https://www.nfsa.gov.au/sites/default/files/11-2016/nfsa_pres_lightblue.jpg

Film repair

The aim of film repair is to permit the film to be safely transported through some form of film handling equipment such as printers, projectors or telecines.

Repairs should be durable, thin enough to prevent undue movement as the frame passes through the gate, maintain any shrinkage along the length of the repair, neatly trimmed so there are no overhanging pieces that can catch and must maintain the correct rack or number of perforations per frame – in the case of 35mm film there are four perforations per frame.

Splice repair

Repairing a cement splice

The first step in re-cementing splices that have broken apart is to gently scrape away the dried cement. To accurately realign the two sections of film it might be possible to use a commercial splicer, depending on the degree of shrinkage. If the shrinkage is too great then a splice can be made entirely by hand using the following method.

Clean up the broken sections of film by gently scraping away any dried cement with a scalpel. Take care not to scrape too deeply as this will weaken the film base. If the base is scraped too far the splice will not form a good loop and will will be unstable during transport. It will also tear more easily.

Tape one section of the film by its edges to the workbench, carefully align the second section using a straight edge as a guide and another piece of film to ensure the perforation pitch is correct, Fig 11.1 ii.

When the film is correctly positioned tape one edge down so that the film can be lifted, Fig 11.1 iii.

Lift the free edge of the film and apply the cement from the centre out along the splice edge, Fig 11.1 iv. Don’t apply to much as the cement may bleed out of the repair and mark the surrounding film leaving a blemish. Press down gently for a few moments. Repeat on the other side, again making sure no cement spills from the repair area.

A small piece of folded paper that goes under the fixed section of film and over the other section of film will absorb any excess cement and prevent finger marks on the film.

Tape splicing

Sometimes if the splice has been poorly made originally, or poorly repaired at some stage, the base will be very thin caused by too much scraping. A cement splice would require the loss of a frame as there may be too little film left to effectively splice too. To prevent the loss of a frame splicing tape can be used, however tape does raise a few concerns on the preservation of the film.

Tape splicers are designed for release prints and have long pitch and cutting teeth that match the KS perforation shape. If the film is at all shrunken then this is an unsuitable technique as the cutters will cut away sections of the film around the perforations making the film less stable during machine transport.

Not all tapes are suitable for use with photographic materials, any tape used must be tested for compatability with a Photographic Activity Test (PAT).

Over time, even with tapes that have passed the PAT, the adhesive may spread or 'creep’. This can cause the film to attract dust or stick together. In either case the adhesive residue will need to cleaned off

To tape by hand carefully align each section of film (as in the previous technique) and apply tape to the base only. Trim the excess away using a metal straight edge and sharp scalpel. Cut the tape away from the perforations using a pointed scalpel blade.

Butt splice

Fig 11.2 Butt splice repair section NB: image is too low rez to use)

Alternatively, a butt splice can be made. Clean up the broken edges of the film, align the two parts, emulsion down, so that the pitch of the perforations match. Tape the films down with a small section of masking tape so that the tape does not cover the splice area. From a piece of scrap film cut a small section to be used for reinforcing shaped as in Fig 11.2.

Scrape all the emulsion off the reinforcing section and align it across the splice. If you wish you can tape one edge of the section to hold it steady while you apply the cement. Working from the centre of the repair piece out, apply the film cement. Do not used to much cement otherwise the splice will be weaker. Hold the repair piece in place for a few seconds. Then working from the centre again, cement the other side.

Butt splice repair — Fig 11.3 Butt Splice

When removing emulsion to make any repair it is important to make sure that all the emulsion is removed from the area where you wish to apply film cement. If you don’t then the splice will not be strong and will probably break when the film is used.

It is also important not to scrape to much away. If too much film base is scraped away, then the chances are that the cement will cause the repair to buckle.

Hand splicing

Finally you could remove one or two of the frames and make a new splice. This may not be desirable for a number of reasons. If frames are removed then any sound components, such as sound negatives, will fall out of sync. Again if there is a sound component on the film then sound will be lost from the scene twenty frames ahead.

If you decide that the only successful way of repairing the film is to make a new splice then the following technique will allow a hand built splice that maintains the shrinkage.

Trim the film as shown in Fig 11.4 i and ii. Scrape all the emulsion away from the frameline on the film with the edge flaps. Lightly scrape the base side, this is just to ensure that the cement has some 'fresh’ base to bond to.

Trimming the film 3 — Fig 11.4 iii Overlap

Use the perforations to align the film sections, Fig 11.4 iii, emulsion down. It may be helpful to tape one of the pieces of film down. Apply film cement along the scraped section and press the films together.

The perforations that were used to guide the position of the films ensures that the exact shrinkage of the film has been matched during the repair.

Sometimes splices will be found that have buckled with age. These were probably due to a poor attempt at repair at some stage in the film’s life. These splices will cause the image to jump during transport and so should be repaired. With care it is possible to pull an old splice apart. The trick lies in deciding which option to use for the repair.

Perforation repair

Perforation repair tapes are available commercially and the time saved by not having to cut the tape away from the perforations is worth the expense of the tape. Again the issue of shrinkage appears. Perforation repair tape is designed for unshrunken film. However, if it is used to cover no more than four perforations at a time then the effect of the difference in shrinkage is usually marginal. All that is required is care in aligning the perforations in the tape with those on the film.

If the film surrounding perforations is significantly damaged or missing altogether then a technique called 'bridging’ is useful. The bridging technique attaches a different piece of film, with identical shrinkage, to replace the original perforations.

Bridging

Clean up the edge of the film by removing any odd pieces of film that may catch during transport (Fig 11.5 i).

Select a suitable piece of scrap film ensure that the shrinkage is nearly identical (Fig 11.5 ii) and trim it so that there are two or three perforations extra at each end. Cut this film down the centre line. This gives a nice handle to work with while you are aligning and cementing the bridge.

Clean the emulsion off the repair piece and gently scrape the ends of the film where the bridge is to be attached. Align and overlap with the perforation at each end of the repair and cement the new section (Fig 11.5 iii).

Finally, trim the handle away using a sharp scalpel and a straight edge (Fig 11.5 iv).

There is no need to cement down the centre parts of this repair unless it runs for several frames. If this is the case then a drop of cement every two or three frames is sufficient.

Repairing tears in film

When a film tears there is invariably a small overlap of emulsion. When aligning the film it is critical that this small flap of emulsion is in the proper position, otherwise a very obvious line will be visible along the tear.

Align the tear so that the emulsion flap is sitting over the top of the base and hasn’t been tucked underneath.

Tape the sides of the film down so that nothing moves while the tape is applied across the film.

Work from the end of the tear if the film is still in one length, or from one end if the film is in two pieces. Place a piece of tape across the entire width of the base. Align the edge of the tape so that both sides of the repair tape align with the frame line of the film. If the tape is carefully worked across from one side of the film to another then very few air bubbles will form under the tape.

Emulsion flap repair air bubble — Fig 11.7 iv

If any air bubbles do form, use a cotton bud to smooth them carefully to the sides of the tape. If a bubble forms that cannot be carefully worked away, gently pierce the surface of the bubble with either a scalpel or needle. This will allow the air to escape. Smooth the tape down.

Work back to the head of the tear covering one frame at a time.

Cut the tape away from the perforations and trim the edges so that there are no sections of tape that can catch along the edge of the film.