Back to

A Discussion of Orotones

In February of 2012, the Indianapolis Museum of Art mounted a works on paper exhibition created by IMA Prints, Drawings & Photographs Curator Marty Krause entitled “Looking West.” This exhibition featured collection prints, drawings, photographs and watercolors by artists of the 19th & 20th centuries who were captivated by the scenery and culture of the American West. Two of the photographs chosen for this exhibition were taken out of storage for the first time since their acquisition in 1988. They were listed in the museum’s database as works by Edward Sheriff Curtis and identified as “orotones.”

Edward Sheriff Curtis, “Three Chiefs Piegan,” 1900. Gift of Mrs. Charles E. Rogers. 1988.65

It is one of my responsibilities to inspect every artwork prior to display in our galleries to make sure that there are no compelling condition problems that would require treatment before the installation. The orotones were stored with the oil paintings, hanging high on massive wire mesh storage racks suspended from the ceiling. I had to climb a ladder to reach them, and at the top I leaned forward to remove the archival foamboard light shields that were fitted around their frames to protect them from unnecessary light exposure. What I uncovered were two gleaming images, casting a quiet golden glow that seemed slightly miraculous given the cold illumination provided by the overhead fluorescent lights. The orotones shone as if lit by internal church candles, and I was immediately intrigued by the beauty and presence achieved by this esoteric photographic process.

Edward Sheriff Curtis, "The Vanishing Race," 1904. Gift of Mrs. Charles E. Rogers. 1988.66.

Edward Sheriff Curtis, “The Vanishing Race,” 1904. Gift of Mrs. Charles E. Rogers. 1988.66.

Edward Sheriff Curtis was both prominent and prolific in the history of orotone images. His most famous endeavor involved amassing a documentary record of Native American cultures through staged scenes and portraiture, and the use of this particular technique enhanced the romantic appeal of this body of work. The IMA photographs are entitled Three Chiefs, Piegan and The Vanishing Race. They were in identical frames of gilded wood with decorative corner elements, and I came to learn that these were a common type of frame associated with Curtis’s work, personally selected to properly enhance and dignify his images.

Detail: lower left corner of the frame belonging to “Three Chiefs Piegan.”

What are orotones? This turned out to be a much more complicated question than anticipated. Other names for them include Goldtones and Curt-tones, the latter term coined by Curtis himself. The Latin word for gold is aurum, approximated by the prefix ‘oro’ which seems an obvious reference to the golden appearance of the images. This has lead to the misunderstanding that all orotones utilize actual metallic gold within the process. In truth, Curtis’s orotones were created by projecting a photographic negative onto a glass plate that had been pre-coated with a silver-gelatin emulsion, thereby creating a ‘positive’ image. The image was developed and fixed, and the emulsion was then coated with a layer of ‘bronzing powders mixed with banana oil’ to produce a backing color that enabled the highlights and shadows to be discernible, thus rendering the image readable. The ‘bronzing powders’ (metallic powders in a liquid carrier) were probably variable mixtures, but in Curtis’s work, they have been found to contain copper and zinc (note: bronze is technically defined as an alloy of copper and tin; copper and zinc are the components of brass). This metal combination was confirmed at the IMA through a brief scan using a handheld X-ray fluorescence spectrometer. The ‘banana oil’ is amyl acetate in acetone and benzene, with the addition of a small amount of proxylin, which is a cellulose nitrate lacquer. The amyl acetate solvent is produced synthetically, but it has the distinct smell and taste of bananas, which explains the persistent use of the term ‘banana oil.’ It takes a great deal of skill to lay this coating over the emulsion flawlessly, which may help to explain the relative rarity of this process and Curtis’ justifiable pride in his mastery of the technique. He is even thought to have modified the materials to gain the precise aesthetic that he wanted, although this speculation has not been well documented.

Now that we understood what orotones were, we knew that we needed to re-examine our stewardship practices surrounding them to make sure that we were giving them the care they needed in order to survive into the distant future. It is very fortunate that we have the advice of visiting photograph conservator Paul Messier (which I wrote about here), contracted by the IMA for a condition survey of all collection photographs through a generous grant from the Institute of Museum and Library Services (IMLS). The following information is excerpted from Paul’s survey of The Three Chiefs, Piegan:

About Orotones

The object is properly described as an “orotone.” The photographic image is rendered as a positive transparency on the glass plate. The image is silver-based, bound to the glass with a gelatin emulsion. The unprocessed / unexposed gelatin glass plate would have been commercially prepared. Once the positive image was exposed onto the plate and then developed, fixed and dried, the emulsion surface was coated with bronze powders evenly dispersed in a binder [this would be the ‘banana oil’ so often mentioned in the literature; however, Paul suspects that other substances were sometimes used]. The binder medium varies and, at times, it can remain somewhat tacky. Quite often the plates are backed with a lightweight paperboard sometimes affixed to the plate with a paper tape. The Art Nouveau/Arts and Crafts frame is typical for Curtis orotones and is original and intrinsic to the piece.

What Can Go Wrong

Typical problems with orotones are separations or flaking of the bronze powder layer from the reverse. Attempts at consolidating such defects can be disastrous and should be avoided at all costs (the consolidating medium penetrates into the gelatin and between the layers, altering the refractive index of all layers and causing a dark, irreversible, stain). Careful handling and leaving any backing board found on the reverse undisturbed are crucial for avoiding such separations.

Cleaning the Glass Surface

An important and often neglected fact is that the glass surface is the primary support for the photograph. To the extent possible, the glass surface should be cleaned using dry methods, as liquids can seep around the edge of the plate and disturb the adhesion between the various layers.

Transporting Orotones

The object is extremely fragile. The glass is intrinsically delicate and the adhesion between the bronze powder layer and the gelatin emulsion is easily disturbed. Orotones should not travel unless it is absolutely necessary [due to the dangers of travel-induced vibration]


Rack storage with required light shields. [Note: temperature and humidity extremes should be avoided]


5-7 FC (footcandles, about 50 LUX) with limited duration. Light intensity and duration of exposure should be recorded [as light-induced damage is cumulative].

I am personally delighted to have discovered the world of orotones. They have a beauty that is unique and captivating, and a look at several photographic forums online reveal that contemporary photographers are beginning to stride into the challenges of this process. I would like to give Edward S. Curtis the last word in this blog: he described the wonder of orotones [here called Curt-tones] in this famous passage that he penned for a brochure advertising his studio in 1903:

“The ordinary photographic print, however good, lacks depth and transparency, or more strictly speaking, translucency. We all know how beautiful are the stones and pebbles in the limpid brook of the forest where water absorbs the blue of the sky and the green of the foliage, yet when we take the same iridescent pebbles from the water and dry them they are dull and lifeless, so it is with the ordinary photographic print, but in the Curt-tones all the translucency is retained and they are as full of life and sparkle as an opal.”


Filed under: Conservation, Photography, The Collection, Uncategorized

4 Responses to “A Discussion of Orotones”

  • avatar
    Kathleen Says:

    Really interesting Claire. Thanks for sharing this!

  • avatar
    Julian C. Says:

    Hello, In reading your article, it appears likely that most of your information on the history, creation and construction of orotones was taken without credit from the website “Orotones: The Golden Messenger of Early 20th Century American Culture” ( I say this because there is no other published material out there presents all this information (the website was launched in May of 2011, before Paul Messier October 2012 survey you mention). Christy Hansen, therefore, deserves mention/information credit in this article, as I am sure that she did intense research to present all this material.

  • avatar
    Claire Hoevel Says:

    Hi Julian,
    Thank you for directing our readers to this website, which is a much more thorough treatment of the subject of orotones than our cursory blog entry; anyone interested in orotones should find Christy Hansen’s work a truly comprehensive look at this photographic process. Our blog was based on the common knowledge held by conservators and conservation scientists who have made career studies of photographic processes. The professional team assembled at the IMA for work on the IMLS grant is especially qualified to offer information regarding orotones based on both personal experience in treating orotones and concerted involvement in the analysis of photographic materials. It is hoped that the study of historic orotones will constantly evolve as more examples surface and better analytical techniques are developed that will not involve direct access to the media layer. We can all look forward to more information coming forward in the future. – Claire

  • avatar
    Steve Says:

    This post is very interesting. You’ve combined multiple perspectives on a very intriguing photographic process.

  • Trackbacks