Chapter 7
Daguerreotypes, Ambrotypes, and Tintypes

This chapter discusses Daguerreotypes, tintypes, ambrotypes, and ambrotype derivatives Hallotypes, Diaphanotypes, spherotypes, and alabastrines.

Specimens of Daguerreotypes, ambrotypes, and tintypes are sometimes mistaken for each other in similar decorative cases. Daguerreotypes and ambrotypes were always cased; only tintypes were both cased and uncased. When cased, tintypes resemble ambrotypes on cursory inspection. The normally rather obvious differences in the three types are often obscured by deterioration and by original process variations. Unlike paper photographs, however, these three types did not fade. It took many years to recognize and control impurities in paper and gelatin, and in processing chemicals.

Daguerreotypes
The literature on Daguerreotypes is phenomenal in physical volume and in the vitality of modern research. Virtually all photographic history books contain accounts of the invention and worldwide acceptance of the process from about 1840 to the mid 1860's. The calotype made only minor inroads in its popularity, even though the calotype negative permitted duplication, while the Daguerreotype had to be rephotographed or etched and inkprinted. The wet collodion and tintype processes finally superseded the Daguerreotype, but it left a rich legacy of some of the earliest historical photographic images.

Besides the standard history books, Gernsheim [61], Barger [8], and Newhall [104] have separate histories of the Daguerreotype, based on historical and cultural factors. The process has been revived in recent years, notably by Irving Pobboravsky of the Rochester Institute of Technology, with beautiful results. Romer [126] estimates that there are or have been several dozen modern practitioners of the art.

The Daguerreotype has been studied more extensively by modern analytical methods then any other historical photographic process. Most of the results to date are listed in the bibliography under Modern Scientific Studies. The definitive work has been reported by M. Susan Barger and her collaborators [references 7 through 18]. In particular, Barger and White, reference 15, is a work of major significance, not only regarding the Daguerreotype but also parallel branches of photography in that period. Other work is by Pobboravsky [118 and [119], Swan et al [138], and Jacobson & Leyshon [80]. A scientific model is described by Barger [8 and 12]. Modern scientific interest in the process is aroused by its embodiment of thin film physics and optics. It is the only completely inorganic chemical photographic system with no emulsion, which makes it an interesting model for photosensitive research.

Daguerreotypes are probably the easiest of the three cased types to identify because the polished silver exhibits specular reflection. This means that they are silver mirrors in which the viewer can see a true image reflected, not just a metallic sheen. The appearance depends critically on the viewing angle.

The nature of the Daguerreotype image is shown in scanning electron micrographs in Appendix I. Highlights in the image contain a high density of light - scattering amalgam particles, so that some incident light has a good probability of reaching the viewer's eye. Shadows have fewer such particles, so incident light is efficiently reflected away from the eye unless the viewing angle is very close to ninety degrees. In the latter case, the viewer will see his or her own image.

The polished silver is a property unique to Daguerreotypes and a valuable aid to recognition, but there are two problems. First, the silver is subject to tarnishing, especially around the edges as shown in Figure 5. Second, all Daguerreotypes have protective glass over the picture, and reflections from the glass can be mistaken for reflections from the silver. This may confuse identification because all ambrotypes and some tintypes were also glass covered.

Figure 5

Daguerreotypes were made in standard sizes (not all authorities agree on these sizes):

In addition, there was a "double whole plate", also called Mammouth or Imperial plate, 10 1/2 x 13 1/2 inches. This was the largest Daguerreotype size ever made, and a few were made about 1850. According to Condax [35] no camera capable of holding these plates is known to exist today.

Most Daguerreotypists bought whole plates and cut them to desired sizes, using much ingenuity to minimize waste. Rough cut edges and corners are common, concealed in the cases. Blank plates were supplied to the trade, mostly from French and American sources, and were made by two processes: (1) electroplated silver on copper, and (2) cladding.

Cladding was discovered about 1742 by Thomas Boulsover. It is a process of fusion bonding by alloying a bar of silver against a bar of copper and running them together through a rolling mill under great pressure. The process is described in Bisbee [23]. The silver thickness of clad plates was one-fortieth to one-sixtieth of the copper thickness; the number 40 was often stamped in one corner of whole plates. Clad plates were used for the earlier Daguerreotypes, while electroplated plates were later used by some Daguerreotypists.

Electroplating was patented in 1840 and put into practical use about 1844; it depended on the availability of electric current. 'Galvanic' batteries were used as a power source, and electroplated plates were called 'galvanized' (modern usage of the term refers to hot-zinc dipping). Pobboravsky [119, 42] states that French electroplated Daguerreotype plates were made as early as 1851, with an embossed hallmark of the process.

The microstructure of the silver surface is different in the two processes. Rolling generates minute longitudinal marks, while electroplating produces a more porous grain structure which can be seen microscopically. Fusion bonding also produces some alloying of the copper in the silver, which varied with process parameters. In principle it should be possible to trace the source of a plate by analysis of these characteristics. Both processes are common metallurgical operations today.

The sensitized plates were exposed directly in the camera, generating a reversed image (see Chapter 11), but not quite all Daguerreotypes are reversed. Some are rephotographed copies, so that shop signs, for example, read normally. Others were made by photographing through a 45 degree prism mounted in front of the camera lens, or from a mirror. Both of these techniques produced a normal picture but were not often used because they were too much trouble and expense. People were so entranced with the novelty of fixed images that it didn't really matter if portraits were reversed.

There have been several published processes in the past few years for removing tarnish from Daguerreotypes. It is strongly recommended that none of them be used without first reviewing the most recent techniques: see the comments in Chapter 12 and Appendix I. Cosmetic reasons are not sufficient to justify the risk of irreversible loss of image information.

Ambrotypes
Ambrotypes were more popular in America, appearing from 1854 until about 1865; their European name was amphitype. They are collodion negatives (not positives) on glass, sandwiched against dark background materials in a case. They appear as positives for the following reason. When any transparent silver based negative is viewed from either side, a small amount of light is reflected back to the viewer from the shadows; essentially no light is reflected from the highlights. This is difficult to verify in a brightly lighted room because so much light comes through the negative, but it can be seen in a darkened room with the illumination coming from behind the viewer. If a matte black surface is placed behind the negative, it will prevent any light from coming back to the viewer from the clear regions, transforming them into shadows. Light will still be reflected from the darkened areas of the negative and they become highlights relative to the clear areas. Thus the negative now appears as a positive, though not very bright or contrasty by modern standards. Daguerreotypes were usually not very contrasty either, so ambrotypes became competitive, especially since they were cheaper.

Ambrotypes often look like they were made on a dark and stormy night. Efforts were made to improve the contrast; exposure and development techniques were optimized, and tinting helped to relieve the dullness. Different kinds of background were used; japanned black cardboard, velvet, black varnished metal, and black varnish applied directly to the collodion negative. Towler [108, 138] lists four varnish formulations that could be applied to either side of the glass negative. If it was applied to the collodion side the picture was not reversed to the viewer but it was duller than if the glass on the side opposite the collodion was varnished. Most ambrotypes are reversed as a tradeoff for a slightly brighter appearance.

Varnish on the glass is often blistered after a century and a quarter; in such cases the picture appears hideous and apparently worthless, but there is hope of restoration. The picture can be restored by removing the old lacquer; this is a task for a skilled restorer who knows which solvent will remove the varnish and not the collodion picture. Black paper (acid-free archival quality) will then restore the picture if the collodion image is intact. Sometimes just placing black paper against the blistered varnish will improve the appearance, but it is not a proper restoration and it may abrade the collodion if that is the side that was varnished. Neither Daguerreotypes nor tintypes show this particular form of deterioration, so blistering is at least an aid to identification. Figure 6 shows an the component parts of an ambrotype that is backed with a piece of black lacquered iron with formed raised edges to prevent close contact with the glass. The collodion surface can thus face the backing without abrasion damage, and the picture is not reversed. This backing has survived without deterioration. The image photographed on a white background can be seen to be a negative.

Figure 6

Figure 7a	Figure 7b

Note that in paper processes, shadows (not highlights) are rendered by heavy silver deposits in the negative, and positive prints are produced in a second step from negatives. Highlights in paper prints derive their color from the underlying paper stock.

Some tintypes are very dark overall while other specimens have surprisingly good contrast with an almost white background that is independent of viewing angle. Crawford [38, 43] mentions that a grayish white background could be created by adding mercuric chloride or nitric acid to the developer. Neither Eder nor Towler mention this process, but there are striking variations in the contrast range of different specimens, for which we have been unable to establish a date correlation. The tricks used by individual practitioners often interfere with hopes of finding a convenient historical progression for dating.

Tintype plates, like Daguerreotypes, were exposed directly in the camera and therefore were reversed, but again there are exceptions. In addition to copying, and the use of prisms or mirrors, the collodion image could be transferred to another metal plate. The resulting picture was called, naturally, a transferotype and was rereversed, or normal. Further, the final metal base did not have to be japanned iron and the magnet test fails if it is, for example, copper or brass. These exceptions are relatively uncommon (we have no frequency data), but the serious historian should be aware of the possibilities.

Estabrooke's book [51] contains inserted 'non-reversed' tintypes "made by the identical processes offered in this book", but he fails to describe the 'non-reversal' process. However, he describes the 'copy stand' in his darkroom and it can be inferred that it was used. If he had used a prism at the camera lens (see Chapter 11), one would have expected him to mention it in his detailed description of his 'glass room', or studio.

The collodion surface of tintypes often shows fine crazing or cracking, which distinguishes them from ambrotypes. Remarkably, many tintypes show no trace of rust in spite of bends and scratches. At one time it was fashionable to adorn tombstones with tintypes, and a few have survived a century of outdoor exposure.

Tintypes were made in many sizes with little standardization. The largest was 6-1/2 x 8-1/2 inches. The base material was cheap and many tintypes are very roughcut and irregular. Some were mounted in Daguerreotype or ambrotype cases; they can usually be identified with a small magnet. Tintypes were often glued on small paper mounts or mounted as cartes-de-visite. The tiny Gem tintypes (1 x 1 3/8 inch - see Figure 8) were sometimes mounted in stamped brass frames that resembled Daguerreotype frames; these frames were then crimped on cardboard mounts. But the majority of tintypes were simply unmounted; in this form they could be mailed easily and cheaply, making them popular during the Civil War.

Figure 8

Many tintypes are rather grubby in appearance, as Crawford aptly describes them, and art critics universally turned up their noses. Aesthetically they were no match for the elegant platinotype. But they are durable and unfaded after more than a century, and today they remain a plentiful legacy of the appearance of Civil War soldiers, celebrities, period clothing, and architecture.

Direct Positives
Daguerreotypes and tintypes were direct positives and were commercially very successful, even though they lacked an intermediate negative for reproduction. Many inventors strove for the simplicity of single step positive processes and there were some successes. But why does a light-struck area of the sensitive surface appear light after processing in spite of the earliest observations that silver salts darken when exposed to light?

In both tintypes and Daguerreotypes, the light from highlights in the subject produces a chemical change in the sensitive surface. In the Daguerreotype, nucleation centers in the highlights are converted to dense concentrations of mercury-silver amalgam particles. These particles scatter more reflected light to the viewing eye than does the surrounding area with no particles, resulting in a "positive" image. In the tintype there are no amalgam particles, but the reduced silver particles in the highlights are more reflective than the dark backing without silver particles exposed in the shadows. Both processes relied upon the difference between reflectivity from the highlights and from the shadows: there was a better chance of light reaching the viewer from the highlights than from the shadows.

Neither process worked on white paper, and both processes were marginal in their contrast control compared with modern processes.

Japanning
A description of japanning is in order, since it is rarely described in photographic histories. Perry [111, 18] has a useful description. Essentially it consists of baked lacquer, usually applied in multiple layers to sheet iron, and baked between each coat. The composition of early lacquers was sometimes a trade secret, but Estabrooke's formula is simply asphaltum (tar) in linseed oil. Tar is available from many sources in nature, with variations in impurities, and japanning quality was no doubt correspondingly variable. In Europe japanning dated to the early 17th century, and in the East much earlier. The original motivation was decoration, but it also formed a very durable and rust-resistant coating that compares favorably with some of our modern polymers.

Collodion images were sometimes printed or transferred (these were two separate processes) on to japanned cardboard or leather. In these cases the finish was air dried black varnish; Towler [145, 150] has a simple recipe. True japanning requires high temperature baking cycles that could not be used on flammable materials, but many black varnishes or lacquers acquired the generic term of japanning. For restoration purposes it is not safe to assume resistance to any particular solvent.

Japanned lacquer was produced in various colors besides black; only the "chocolate" plate, patented in 1870, became as popular as the black, and there are many surviving brown specimens. The brown color was thought to be more lifelike; the same thinking may have accounted for the popularity of sepia paper prints. But gold or sepia toning was widely used on paper prints to combat fading, so public acceptance of brown may have been a factor. Tintypes and ambrotypes did not fade unless they were grossly underfixed or washed, whereas paper prints suffered chronically from fading problems for many years.

Tintype Nomenclature
Tintypes, the name most often used today, were also called Ferrotypes, Melainotypes, Melanotypes, Melaneotypes, Ferrographs, Adamanteans, Adamantines, and several other trade names (see Estabrooke, [51]. These names reflect minor trade differences, but they are all collodion-silver images on japanned iron. The evolution of the many trade names is complicated and illustrates the problems of assigning a single identity to what now appears to us a single process. The following account is largely paraphrased from Estabrooke's 1872 book [51].

Smith's invention is usually dated as 1854, but the date of publication of his patent is February 19, 1856. Smith called it the Melainotype, and Estabrooke says it was based on a French invention of a black enamelled plate "for photographic purposes" called the Melanotype plate. Apparently Smith's contribution was to coat the Melanotype plate with collodion containing a solution of silver salts.

Peter Neff bought Smith's Melainotype patent in 1856 (Eder says 1857) and continued manufacture for several years. At about the same time (1856) Mr. V. M. Griswold of Peekskill New York introduced his Ferrotype plates in defiance of Smith's (now Neff's) patent. By this time the market was a free-for-all of competing processes and tradenames, and one writer, in disgust, referred to the various processes as 'hum-bug-otypes'. This same writer favored the Melaneotype (sic), adding a new name to the confusion. Some other tradenames were Adamantean, Phoenix, Vernix, Eureka, Excelsior, Union, Star Ferrotype - all collodion silver on japanned iron. Finally in 1870 the Phoenix Plate Company introduced the "chocolate" plate which was a sensation, short lived because the advent of chlorobromide paper was imminent. Estabrooke remarks that "...in those times every unimportant change was called a new process."

Mr. Griswold issued a rather plaintive statement concerning the many trade names:
"Many other names have been given to similar plates, such as Adamantine, Diamond, Eureka, Union, Vernis, Star Ferrotype, Excelsior, and others, among which the most senseless and meaningless is 'Tintype'. Not a particle of tin, in any shape, is used in making or preparing the plates, or in making the pictures, or has any connection with them anywhere, unless it be, perhaps, the 'tin' which goes into the happy operator's pocket after the successful completion of his work. None of these names, however, have been considered so apt and appropriate as Ferrotype, and it will, doubtless, be generally accepted as long as the pictures are known." Alas, Mr. Griswold, for your optimism.