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Transferring Nitrate-base Motion Pictures To New Stock1

(by Warren Kingsley)



The photo unit of the National Archives successfully duplicated films that otherwise would have been lost to history.

The National Archives Photographic Services Branch, (A self-sustaining entity operating under the Trust Fund of the Archives) is known industry-wide as a dependable source of top-quality stock historical footage, and is something of a watershed when it comes to film preservation techniques. In 1979, it produced about 5 million feet of motion picture footage, some of which was sold to the television networks and individual stations producing documentaries.

The branch sells duplicated prints of old newsreels, outtakes, World War I and World War II footage, and other film clips to meet buyers' requirements. This fee service is patronized by various private groups with historical interests as well as by the motion picture and broadcasting industries.

The branch's principle responsibility is to help preserve the 100 million feet of motion picture film stored by the National Archives. Under normal conditions this requires considerable expertise. The challenge is even greater for black and white films recorded from 1916 through the mid-1950's. Most of this film was recorded on nitrate-base stocks made by various manufacturers.

During the past several years the photographic branch has become recognized as one of the leaders in the development of techniques and technology for restoring this valuable footage.

All of this nitrate-base film is subject to deterioration with aging. However, the rate of deterioration depends on the way the film is stored. High temperature and high relative humidity, for example, accelerate the rate of deterioration.

"One of the problems was that all of this footage came from sources who stored it under widely varying conditions," says Richard Youso, director of the Photographic Services Branch. "Some of it was still in very good condition. In other cases, the film base was shrinking because of the loss of plasticizer and emulsions were becoming sticky."

There was also an important safety consideration hastening the need to copy these older films onto new stocks: Nitrate base becomes more unstable- and flammable- with age. "This should be a consideration to anyone still storing nitrate base films," Youso says.

The problem was highlighted when a fire destroyed nearly 10 million feet of nitrate-base footage in Archives' vaults in December 1978. Universal Studios' newsreel outtakes were among the footage lost in the fire.

Aided by the Congressional appropriations earmarked for preservation, the branch embarked on a crash program to duplicate the nitrate-base footage. The results: 7 million feet of nitrate footage, including negatives and master positives, was converted onto polyester and acetate -base 35mm stocks.

The effort required extensive overtime, special equipment, and equipment adaptations, and the developments of a new film stock. Working for 14 months, lab technicians duplicated the nitrate-base stocks. Youso recalls that the odor of these films ran the gamut from mildly acidic to a downright pungent acetic odor, indicative of advanced deterioration.

"There was really no reliable way to distinguish the older rolls from the newer ones," Youso explains, "since the various manufacturers of nitrate base stocks tended to alter the amounts of nitrate and plasticizer in the base from time to time."

Working exclusively on the project, eight technicians printed 3 million feet of master positive, nitrate-base footage onto Eastman fine grain duplicating panchromatic negative film 5234. The remaining 4 million feet - negative footage- was printed positive onto Eastman television recording film (Ester base) SO-474, a product the division played an active role in developing. The special order stock consists of the emulsion of Eastman television recording film 5374 coated onto an Estar base.

"We wanted a polyester base for the dimensional stability necessary for archival quality," Youso explains. "We paid $5,000 up front for the stock's development which, of course, did not begin to cover Kodak's costs. The only requirement was that once the stock was developed, we had to order a minimum of 80,000 feet."

Before making the special order, the divisions laboratory conducted extensive testing on the 5374 stock and found it suitable for the purpose at hand.

"When the first batch came in, we did more testing to pinpoint any variables introduced by the Estar base," Youso explained.

The polyester-base stock performed as hoped- exactly like acetate-base film.

There was another reason why the special order film was needed. Youso had acquired a Logetronics SP 1070 printer (for aerial film) that had been uniquely converted to print 35mm perforated film. The printer which uses a cathode ray tube as a light source improved reproduction speed on some of the footage by saving prep time. The device was soon nicknamed "the Gray Ghost."

"We needed a film that would be appropriate for the amount of energy the CRT emitted and match the spectral response of the tube." Says Youso. "While Eastman fine grain duplicating positive film 5366 is an excellent material, we needed a film that was more adaptable to that set of criteria. As it happened , 5374 met those criteria. "Our testing showed that the two emulsions were kissing cousins." Says Youso, a member of the Society of Photographic Scientists and Engineers.

Before the duplication of the nitrate footage on the new stock could begin, branch technicians had to work overtime during Christmas holidays to salvage about one million feet of footage still wet for the December 8 fire.

"We had to rewash the wet film, put it on new cores, and then in new cans," recalls Dave Cmeyla, photographic supervisor for the branch's motion picture division.

The duplication work began in January 1979 and ended in March 1980.

"We duplicated only about 100,00 feet the first month," says Cmeyla, who formerly worked for the Navy's Photographic Center Library. "As we standardized procedures, we improved production to around 500,000 feet per month."

The basic printing tools used in the conversion, besides the Logetronics printer, were three Bell & Howell model D printers, two of which had been specially modified.

"The model Ds were the industry standard during the periods that much of the nitrate bases stocks were shot," Cmeyla says.

There was one problem with that logic. "Because of the shrinkage of the nitrate bases, the perforations were too small to fit the printer sprockets," he says. The problem was solved by ordering special sprockets from the Peterson Company. The undersized sprockets had a slightly smaller tooth profile and different rake angle than those on standard model Ds.

An ultrasonic cleaner was used to remove dirt and other foreign matter before the film was loaded onto the printers. In some cases, talcum powder was used as a lubricant to ease the film through the printers.

Using a 500-watt lamp and a lamp setting of 75 volts, technicians operated the printer at 60fpm to copy the negatives onto the master positives of the Eastman television recording film SO-474.

"After setting the lamps for nominal exposures, we ran gray scales and plotted curves to obtain the desired gamma for processing. The gamma usually ran between 1.25 and .3 for the special order stock," says Youso. "Processing was done by a commercial lab."

The footage preserved included March of Time features, Universal newsreels, military training films, World War I and World War II footage, captured German footage, and some award winning films produced by government agencies. Among those were The River and The Plow produced by famous director Pare Lorentz for the U.S. Department of Agriculture.  
"If anything, we achieved superior-quality product over the original negatives and better reversal prints," "says Cmeyla. "The shadow detail was improved, but there was a good tonal range throughout. With the right care during production, those fine grained emulsions on the older stock printed up very nicely," he adds. 


 The Archives' customers agree. "We've done numerous reductions to 16mm from the master positives," says Youso. "We make a 16mm master negative, then convert this to a 16mm release print on various stocks. We have had excellent comments concerning the quality of these prints."

"A lasting lesson from the conversion," says Youso, "was the ability to use the Gray Ghost as an efficient contrast-control device. Using a feedback loop, the device can be adjusted like a television set, controlling the flying spot scanner light source to use it as an incremental exposure control device," he explains.

"The more techniques we develop like this, the better we are able to meet the requirements of our customers, while doing our main job, preserving the history and art that precious generations recorded on film."

1 (From the July 1982 issue of Technical Photography) ,edits and revisions Buckey Grimm 021599
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