US1783895A

US1783895A - Method of restoring shrunken films

Info

Publication number: US1783895A
Application number: US374595A
Authority: US
Inventors: James G E Wright
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1929-06-28
Filing date: 1929-06-28
Publication date: 1930-12-02
Anticipated expiration: 1947-12-02

Description

Dec.2-

, 1930. J. a. E. WRIGHT METHOD OF RESTORING SHRUNKEN FILMS Filed June 28, 1929 Inventor: James G.E.WT i2 ht, Wm

His Attorney.

Patented Dec. 2, 1930 UNITED STATES PATENT OFFICE JAMES G. E. WRIGHT, OF ALILAUS, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK METHOD OF RESTORING SHRUNKEN FILMS Application filed June 28,

My invention relates to celluloid films of the motion picture type which through exposure or age have materially shrunk. It is the object of my invention to provide an improved process whereby a shrunken film may be restored substantially to its original condition.

Referring to the drawing wherein is shown an apparatus useful in carrying out my invention, Fig. 1 illustrates a film supporting frame and Fig. 2 shows a detail thereof.

A common nitrate celluloid film if exposed when new to ordinary atmospheric conditions will shrink as much as one sixteenth of an inch per foot during the first weeks exposure. This shrinkage continues at a decreasing rate as time goes on so that in the course of a year the total shrinkage may be as much as three sixteenths of an inch per foot. Inasmuch as these films are usual- 1 provided with sprocket tooth openings or engaging with driving sprockets, any variation in the pitch of the tooth openings 1 of the film from the original or correct pitch results in improper sprocket tooth action. A small amount of shrinkage, as, for example, one sixteenth of an inch per foot, may in the case of a printer be compensated by a suitable mechanical adjustment of the machine. Such a film also may be passed through the projector without trouble but when the shrinkage becomes excessive through age or continued exposure to the atmosphere serious difficulty is encountered with machines in present use. I have found that films which due to years of storage had become so shrunken that they would not feed properly through the printer or projector may be restored to their pristine condition by the method and the apparatus which I shall now describe.

In the accompanying drawing, Fig. 1 illustrates one form of apparatus which may be used for carrying my invention into effect and Fig. 2 shows an enlarged view of one detail thereof.

The shrunken film is first wound upon a frame which in its general form is similar to those in common use but differs in that the cross bars are adjustably connected to 1929. Serial No. 374,595.

the end frame so as to permit taking up the subsequent extension of the film. In the drawing, the film 1 is shown supported on the frame 2 which in its general character 1s similar to frames for such purposes in common use. It comprises the

end bars

3 and 4 and the cross bars 5 and 6 forming a rectangle over which the film is wound. Cross bar 5 is rigidly secured to the end bars but cross bar 6 is adjustably attached thereto whereby as the film elongates, the slack can easily be taken up. As shown in Fig. 2, the upper end of each

end bar

3 and 4 is formed with a guide slot 8 which receives an end of the cross bar 6. Near each end the cross bar is provided with the threaded stud 9 which extends up through the bracket 10 on the end bar and on which is the winged nut 11. Between the bracket and the cross bar is the coil spring 12.

The shrunken film is wound on the frame in the usual manner with the upper cross bar in its lowermost position. The frame containing the film is then immersed in a tank of water to soften the gelatine emulsion, otherwise the subsequent swelling of the celluloid would injure it. The time required for this softening is the time usually employed when a film is to be developed, which is approximately one half hour. While still on the frame, the film is then immersed in a solution comprising alcohol, camphor, and water, and allowed to soak for a number of hours or until the desired elongation of the film has taken place. In addition to the above I prefer to use a small quantity of ammonia and glycerine, the former neutralizing any acidity of the solution and the latter serving to restore the flexibility of the film. I have obtained very good results using a solution of the above mentioned ingredients in the following proportions Denatured alcohol 3900 0.0. Camphor 97.5 g. Ammonia (.880 sp. gr.) 49 c. c. Glycerine 195 c. 0. Water 5100 c. c.

I dissolve the camphor in the alcohol and add the ammonia and glycerine and last of .2 greases all the Water. This solution has a specific gravity of .944. With this solution the time required to restore a film shrunken about three eighths of an inch ier foot was twelve hours. As a result of soa ing in such a solution the celluloid film swells so that each loop hangs limp on the frame. The amount of extension of the film can easily be measured by comparison with a short piece of unshrunken film or by measuring a few inches of the film with a ruler in which case eight pictures of standard 35 m. m. film should occupy a length of six inches of the film. l-Vhen the film has elongated under this treatment to its original or proper length the movable cross bar of the frame is adjusted by means of the winged nuts to put the film loops under slight tension. The film is then removed and allowed to dry under tension on 30 the frame. When dry the film will be found to have not only the correct length but also the correct width. It is possible to bring the film to the right length in a much shorter time, for example, in as short a time as one and one half hours by keepin the film continually under tension to thereby draw it out. This, however, is objectionable since it distorts the film with the result that after treatment it is too narrow for the printing machine or projector. The length of time required for the swelling of the celluloid is dependent to a certain extent upon the relative amount of camphor in the solution, the strength of the solution therefor and the length of time that 5 the film is immersed may be varied widely from the representative figures which I have given.

WVhat I claim as new and desire to secure by Letters Patent of the United States is:

0 1. The process of restoring a shrunken celluloid photographic film substantially to its original length which comprises softening the emulsion on the film, soaking the film in a camphor solution to elongate it, and drying it while maintained in its elongated condition.

2. The process of restoring a shrunken celluloid photographic film substantially to its original length which comprises soaking the film in water to soften the emulsion thereon,

soaking it in a solution including alcohol,

camphor and water to elongate it, and drying it while mechanically restrained from shrinkage.

3. The process of restoring a shrunken celluloid photographic film substantially to its original condition which comprises soaking the film in water to soften the emulsion thereon, soaking it in a solution containing alcohol, camphor, ammonia, lycerine and water, --.n and drying it while mecianically restrained from shrinkage.

In witness whereof, I have hereunto set my hand this 27th da of June, 1929.

J: H. S G. E. WEIGHT.