When I owned a photo lab, one customer came to me with several hundred 4X5 glass negatives. He asked me to print several examples, just so he could see what he had purchased at an estate sale for a total of $10.00. The family (estate) was selling all of grandpa's "junk", since he had passed away. They were negatives of actors, actresses, and film sets from the silent and not so silent film era of Hollywood, shot on location all over the world. What a gold mine!

Hopefully, I have convinced many people to keep their family treasures, and after they have them printed, identify the individuals in the photographs. Just don't wait too long.

By determining the type of photographic technique used to make your old family photos, it's possible to date, with reasonable accuracy, the date the original was created.

Following are the most common photographic processes. With this information, see if you can narrow down the age of the photograph.
If you need help dating a photo based upon the clothing styles, you can try this site.

from:
PHOTOGRAPHY AS A TOOL IN GENEALOGY
text by Ron and Maureen Willis, Willis Photo Lab 2510 Old Middlefield Rd. Mountain View, CA 94043
(415) 969-3555

DAGUERREOTYPE (1839 - 1870, approx.)
The case resembled a double frame. Very decorative. The photo image is on a silver clad copper sheet which is attached to a sheet of glass by a foil-like brass decorative frame. This sealed packet was then force fit into a special wood case and was often padded with velvet or silk. Many times, the silver image tarnishes with silver sulfide in the same way as silverware. The cost: $5.00 (more than a weeks pay for most people).

CALOTYPE (1845 - 1855, approx.).
The first photographs on paper. A two step process. The first step was to make a negative image on a light sensitive paper. Step two was to make a contact [print] with a second sheet of sensitized paper to make a positive print. Calotypes were never widely popular, and most of those surviving are in museums. Apparently Talbot (the inventor) did not fully realize the importance of washing his prints long enough to remove all the residual chemicals, or perhaps his fixing was inadequate. Either fault leads to the same result: fading image, discoloration, etc. These defects are now noticeable in many calotypes, some of which are today little more than pale yellow ghosts.

AMBROTYPE (1854 to the end of the Civil War)
The ambrotype is a thin negative image on glass made to appear as a positive by showing it against a black background.
Similar to daguerreotype in assembly of parts: 1- Outer protective case. 2- Backing of black paper, cloth, or metal. 3- The on-glass-image, emulsion to the front and black varnish on the back. 4- Brass die cut frame 5- Gilt border of thin brass to edge wrap the frame, glass, and backing.

It was common for the ambrotype to be colored. Suggestions of rouge cheeks or lips suggested a person of substance. Buttons, watch chains, pendants, broaches were often tinted with color.

Disadvantages of ambrotypes: 1. A very slow (up to 20 sec.) exposure, compared to 2 sec. for a daguerreotype. 2. The glass was very fragile. It couldn't withstand travel or being carried in a locket as a daguerreotype could.

Advantage of the Ambrotypes: Price. It could be sold profitably at a low price, approx. 25 cents. The cost of the ambrotype was less than half of the daguerreotype.

THE TINTYPE (1856 to W.W.II)
"The penny picture that elected a president".
Price- sold for a penny or less, making photography universally available. The cost of an image at the time the process became obsolete was about 25 cents.
Advantages: 1. Lighter and less costly to manufacture. 2. Camera was lighter and easier to handle. 3. Wouldn't shatter as a glass image photo would. 4. Could be colored or tinted.

As the public sought lower prices, the cases (which cost more than the finished photographs) were eliminated. In their place, paper folders of the size of the then popular card photographs were used for protection. Instead of a glass cover, the photographer covered the tintype with a quick varnish to protect any tints or colors added to cheeks, lips, jewelry or buttons.

Popularity: The tintype was very popular during the Civil War because every soldier wanted to send a picture of himself with his rifle and sword home. They could be mailed home safely without fear of shattering.

The tintype actually does not contain any tin, but is made of thin black iron. It is sometimes confused with ambrotypes and daguerreotypes, but is easily distinguishable from them by the fact that a tintype attracts a small magnet.

DATING THE TINTYPES
Introduction 1856 - 1860. The earliest tintypes were on heavy metal (0.017 inches thick) that was never again used. They are stamped "Neff's Melainotype Pat 19 Feb 56" along one edge. Many are found in gilt frames or in the leather or plastic (thermomolded) cases of the earliest ambrotypes. Size range from one-sixth plate to full plate.
Civil War Period 1861 - 1865. Tintypes of this time are primarily one-sixth and one-fourth plate and are often datable by the Potter's Patent paper holders, adorned with patriotic stars and emblems, that were introduced during the period. After 1863 the paper holders were embossed rather than printed. Uncased tintypes have been found with canceled tax stamps adhered to the backs. The stamps date these photographs to the period of the Wartime Retail Tax Act, 1 Sept. 1864 to 1 Aug. 1866.

Brown Period 1870 - 1885. In 1870 the Phoenix Plate Co. began making plates with a chocolate-tinted surface. They created a sensation among the photographers throughout the country, and the pictures made on the chocolate-tinted surface soon became the rage. During this period "rustic" photography also made its debut with its painted backgrounds, fake stones, wood fences and rural props. Neither the chocolate tint nor the rustic look are to be found in pre 1870 tintypes.

Gem Period 1863 - 1890. Tiny portraits, 7/8 by 1 inch, or about the size of a small postage stamp, became available with the invention of the Wing multiplying cameras. They were popularized under the trade name Gem and the Gem Galleries offered the tiny likeness at what proved to be the lowest prices in studio history. Gem Galleries flourished until about 1890, at which time the invention of roll film and family cameras made possible larger images at modest cost. It was no longer necessary to visit a studio that specialized in the tiny likeness. Gem portraits were commonly stored in special albums with provision for a single portrait per page. Slightly larger versions also existed. Some Gems were cut to fit lockets, cufflinks, tie pins, rings and even garter clasps.

Carnival Period 1875 - 1930. Itinerant photographers frequently brought the tintype to public gatherings, such as fairs and carnivals. They came equipped with painted backdrops of Niagara Falls, a beach, a boat, and other novelty props for comic portraits.

Postmortems. In the nineteenth century it was common to request a photographer to make a deathbed portrait of a loved one.

THE CABINET CARD (approx. 1866 - 1906).
A card stock product, nearly four times the size of previous photographs on card stock.
The larger size created new problems of photographic quality. Flaws that were not obvious in the smaller cards now became very visible. This gave rise to a new skill of photo retoucher.

Success in retouching led to innovations in the darkroom and at the camera. Diffusion of the image reduced the need for retouching. This led to verbal skirmishes between photographers who insisted in "truth in photography". Opponents called retouching degenerating, demoralizing, and untruthful practices.

Cabinet cards can be further dated by color of stock, borders, corners and size.

QUICK DATING GUIDE TO CABINET CARDS
The earliest American made cabinet cards have been dated only to the post- Civil War period, beginning in 1866. Design and colors of these cards followed those of the cards of that time. Cabinet cards are rarely found after 1906.

Card Colors:
1866 - 1880 White card stock of a light weight.
1880 - 1890 Different colors for face and back of mounts.
1882 - 1888 Face of buff, matte finished, with a back of creamy yellow, glossy.

Borders:
1866 - 1880 Red or gold rules, single and double lines.
1884 - 1885 Wide gold borders.
1885 - 1892 Gold beveled edges.
1889 - 1896 Rounded corner rule of single line.
1890 - 1892 Metallic green or gold impressed border.
1896 Impressed outer border, without color.

Corners:
1866 - 1880 Square, lightweight mount.
1880 - 1890 Square, heavy board with scalloped sides.

Photographs mounted on card stock.
The most popular mount sizes were:
Carte-de-visite 4 1/4" x 2 1/2"
Cabinet card 6 1/2" x 4 1/2"
Victoria 5" x 3 1/4"
Promenade 7" x 4"
Boudoir 8 1/2" x 5 1/4"
Imperial 9 7/8" x 6 7/8"
Panel 8 1/4" x 4"
Stereograph 3" x 7"

REVENUE STAMPS ARE A TOOL FOR DATING PHOTOGRAPHS
As part of the effort by the Congress to fund the Civil War, among a number of taxes levied was an 1864 Act which provided that sellers of photographs affix stamps at the time of sale to "photographs, ambrotypes, daguerreotypes, or any sun pictures", according to the following schedule, exempting photographs too small for the stamp to be affixed:
Less than 25 cents: 2 cents stamps (blue/orange).
25 to 50 cents: 3 cents stamps (green).
50 cents to $1: 5 cents stamps (red).
More than $1: 5 cents for each additional dollar or fraction thereof.

Stamps were applied from 1 Aug. 1864 to 1 Aug. 1866. Blue playing card stamps are known to have been used in the summer of 1866 as other stamps were unavailable as the levy came to an end. The stamp was to be canceled by requiring that the seller cancel the stamp by initializing and dating it in ink. The most rare of all of these stamps is the one cent (red) "playing cards" and the most common is the orange two cent "playing cards". Values for all of these stamps appear in the Scott's Specialized Catalog of United States Stamps.

THE STEREOGRAPH (1849 - 1925).
"Parlor Travel" both educational and entertaining.
The stereograph is an almost identical side-by-side set of images of a single scene, viewed simultaneously through an optical device held to the eyes like a pair of binoculars. Each eye looks at a slightly different image, and the fusion of the two images in the mind creates the illusion of depth. Price: a few pennies.
Sizes of stereo cards and slides: The typical mass manufactured stereo card of the period between the Civil War and WW I had a standard dimension: 3 1/2" x 7". This is the size commonly found in boxed sets. The earliest of these cards were made on slightly curved mounts; later cards were made on slightly curved mounts that permitted greater clarity when they were seen in the stereopticon viewer. A number of photographers, working with larger field cameras, created slightly larger cards of 4" x 7", 4 3/8" x 7" and 4 1/2" x 7". Until about 1873 the smaller sizes were sold at twenty five cents per card and the larger "artistic" size for fifty cents. Within a decade sets of twenty or more were made on printing presses, not by a hand photo-graphic process. The on-glass slides, a stereo form more popular in Europe than in America, were available in two standard sizes, 45 x 107 mm and 6 x 13 cm. Both were smaller than the standard card stereograph.

THE WET-PLATE PRINT (c.1853 - 1902).
"The photograph that opened the West". (A large contact print).
To identify the wet-plate negative, look for an uneven coating were the syrupy colloidal base of the glass plate did not flow to the very edges of the glass. Many of the plate edges reveal torn or rippled emulsion and even the fingerprints of the darkroom technician who handled it with wet fingers. Only occasionally is it possible to determine whether a print was made from a wet-plate negative, especially if the outer edge of the print has been trimmed away. It is the edge that would immediately reveal the irregularities of the coating prepared in the field.
Few Americans could afford the cost of a studio enlargement made with a solar enlarger. The technique of making such enlargements were so complicated that few photographers had the proper skill to make an enlargement from a standard studio negative. Much of the demand for larger photographs could be satisfied by making larger negatives and larger cameras to handle them. Wet plate negatives were often 11" x 14" up to 20" x 24" sheets of sensitized glass.

Wet-plate photographers helped to open the American West by taking their cameras out of the studio and on location assignment with the survey teams of the U.S. Government and the railroads in the Far West, and with the geological expeditions moving into the unmapped wilderness beyond the Rocky Mountains. The giant spaces they discovered demanded giant cameras. The camera that documented the famous meeting at Promontory Point, Utah of the tracks of the Central Pacific and Union Pacific railroads on 10 May 1869 was built to accommodate glass plates 10" x 13". The camera boated down the Colorado River during the Powell Expedition into the Grand Canyon was 11" x 14". The work of these photographers, shown in major exhibitions in Washington D.C., is generally acknowledged to have been instrumental in convincing Congress to enact legislation establishing many of the major national parks, monuments, and preserves. The maps of the surveys showed where everything was; the wet-plate photographers showed precisely what was there.