Black and white photographs that have been stored in a shoebox for sixty or seventy years may be as clear and unfaded today as they were the day they were put away.
And the reason is that the image in black and white photographs is made of very stable silver compounds protected by a gelatin layer on fibre based paper.
Of course, they may be creased or rubbed, but if they were put away carefully that may be all the protection they needed.
Of course, they are not digital prints – that’s a whole other story. For film, the process used today is more or less the same as that from seventy or eighty years ago.
And that process is that in a darkroom, light is shone through the negative onto the paper to produce a latent image. Then the latent or hidden image is developed in different chemicals so it can be seen.
To do that the paper is placed in a bath of liquid developer until the image appears, and then the paper is transferred to a bath of liquid ‘stop’ that stops the reaction. Then the reaction is ‘fixed’ by placing the paper in a bath of a third chemical – and that’s it.
The whole process takes just a few minutes.
And the resulting thin layer of silver compound that is the photograph, protected by a gelatin layer, will remain stable for upwards of one hundred years.
That is not to say that all black and white photographs will be in perfect condition – but if they are not it is probably because they were processed incorrectly in the first place.
For example, the chemical that stops the reaction may have become weak or exhausted so that the development carries on slowly over the years and darkens the photograph.
Resin coated papers
There is a proviso to all this, and that is that with the introduction of resin coated papers for the amateur market in the late twentieth century, new problems arose. Traditional fibre based papers used barium sulphate as the white base. Resin coated papers used titanium dioxide.
And the problem was that the titanium dioxide in the paper reacted with even very low levels of light to produce peroxides that oxidized the silver and make the photo darker than it was when it was first developed.
So resin coated prints from only a few years ago are subject to problems to which traditional fibre based prints are immune.
What we know from all of this is that the stability of the image depends on proper use of the chemicals to produce it, and from the paper on which the image is printed.
Colour Photographs from the 1970s
Colour photograph papers are made with clouds of dye set into the emulsion along with silver compounds. The dyes are activated by light, and when the process is finished there is no silver left in the image – just the dyes.
The early compounds were not stable. They reacted with sunlight, with chemicals in the paper of the pages of the albums in which they were put, with cigarette smoke, with the paper the emulsion was laid on, and not least of all with each other.
Colour photographs from the early days will probably have faded very badly. Some are now no more than a pale smudge.
Thankfully, there have been big advances in colour materials and modern photographs have archival stability to rival black and white photographs.
Environmental Risks to Photographs
That is not to say that colour photographs are immune to deterioration, and it pays to know what the biggest risks to the stability and vibrancy of color photographs are. The biggest risks are sunlight and chemicals.
There are two ways of preventing sunlight damaging a photograph. The first is the obvious one, which is to hang the photograph out of direct sunlight. The second way is to protect the photograph with a sheet of glass that has a UV filter within it. That is an expensive option and there are other downsides, because the colors of the print may look somewhat muted behind UV glass. And of course, many people don’t want to put glass over a photograph at all.
Cigarette smoke and cooking fumes damage photographs, but there are corrosive chemicals in the materials with which the photograph can come in direct contact. The wrong kind of mounting board can attack the print. The board may be made from wood pulp that contain acids that interact with the print. They can cause it to turn yellow and eventually destroy it.
A good framer will know this and will use an acid-free mounting board. These boards are either made from materials (such as cotton rag) that do not contain acids or they have buffer chemicals in them that counteract the lignin acids that are found in wood pulp.
True photographs use light to activate chemicals in the paper. That light may be focused onto the paper in the traditional way with an enlarger. Or the light may be focused digitally with a laser that reads the negative (or even a digital file) and shoots light in a controlled pattern onto the paper.
Whichever method is used, the clouds of dye and silver compounds in the emulsion are activated by the light, and chemicals are used to develop the image and then to stop the development when the image is complete.
But there are prints that are not true photographs because they do not use light on the paper. Instead the printer reads the information in the digital file and uses that information to send colour to the paper.
Inkjets and giclee prints are made by print heads that are controlled by computers and which squirt dyes or pigments onto the paper.
Dyes are solutions of dye materials in water; which means that the dye is dissolved in water and the solution is squirted onto the paper and absorbed into it.
Pigments on the other hand are suspensions of very finely ground insoluble material that is suspended in water. The suspension is squirted onto the paper and the pigment lays on the surface of the paper rather than being absorbed into it.
The distinction between dyes, which are absorbed into the paper, and pigments that do not dye the paper fibers, is important.
Dyes are not color-fast and can fade within a matter of months. Pigments on the other hand can remain light-fast for upwards of 100 years, and are now so stable that they are said to rival true photographs for archival stability. And why not, because pigments are precisely what artists have used for centuries, bound up in oil to create oil paintings.