The Daguerreotype Primer:
Table Of Contents
0. Introduction To Daguerreotypes: Theory & Real-Time Exposure
1. Daguerreotype Substrates: Reductive Silvering, Electrochemical Plating, Roll-Milling, & Exotic Options
2. Selecting A Size For Your Daguerreotypes: Think Thrice, Measure Twice, Cut Once
3. The Plate-Silvering Box: Design & Construction
4. Substrate Preparation For Reductive Silvering: Cutting & Cleaning Of Glass
5. Substrate Preparation for Electrochemical Silvering: Polishing & Cleaning Of Copper
6. Reductive Silvering: The Tollens Process & Its Physical Selectivity
7. Electrochemical Silvering: The Cyanide Process & Its Considerations
8. Silver Mirror Polishing: Preparing Plates For Sensitization
9. Daguerreotype Plate Sensitization: The Halogen Process
10. Taking The Daguerreotype: ISO Benchmarking
12. Mercury-Free Daguerreotype Development: Exploiting Band-Gap Shift
12. Gilding: A Method For Preserving The Daguerreotype Image
13. Encapsulation: Creating A Durable Package For A Photograph
0. Introduction To Daguerreotypes: Theory & Real-Time Exposure
What is a daguerreotype? In short, a daguerreotype is similar to an introduction, in that I’m making one right now. Here is my view camera; this is roughly an 8-by-10 camera, and when shooting film I typically use it as such, but the actual nominal size is slightly larger, at 10-by-12 inches, rather than 8-by-10. Inside is a plate of silver-coated copper, sensitized with iodine vapors, and I’ve been exposing it through my window for an entire week. Yes, I’ve been exposing it through window glass, but before you shout at me that I should have opened the window, because window glass is not optically flat and degrades the image, please keep in mind: I am in Moscow, and it is winter, so you shall forgive me my trespasses, as I don’t want my pipes to freeze and burst; neither do the people who live under my apartment.
Now, I will open the camera, and show you the photograph that has been produced. Similar to other types of chemical photography, it is possible to “print out” a daguerreotype – that is, by exposing the substrate to far more light than is typical, down-rating its ISO, it is possible to make the normally-latent image directly visible, without any sort of development. That is exactly what I have done in this case.
Here is my daguerreotype. It is best viewed under hard light – that is to say, light which comes from a single source, where the paths of photons striking the daguerreotype are nearly parallel. Hard light casts dark shadows, and is typically the lighting condition if you are outside on a sunny day under a cloudless sky – the sun is not truly a point-source of light, but because it is so distant from our beautiful Earth, it behaves nearly as a point-source. In contrast, on an overcast day, as clouds scatter sunlight, we have a “soft” lighting condition: light is striking us, and whatever we’re looking at, from a multitude of angles, and hence shadows are minimized. There are nuances to this – for example, even on a cloudless day, the atmosphere itself will still scatter sunlight, and so at higher altitudes the lighting will tend to be “harder”, simply because there is less atmosphere overhead to perform the scattering. Therefore, the ideal viewing experience for a daguerreotype is to be had by bringing it to the top of Mount Everest on a cloudless Summer Solstice at noon, but we can still have a lovely viewing experience on a sunny day at normal altitudes, or indeed from indoor lighting. Hard lighting is ideal for viewing daguerreotypes, but soft lighting is ideal for filming videos; therefore I’ve made some changes from my usual indoor lighting setup, so that you can see the daguerreotype more clearly. Note that I haven’t fixed this daguerreotype – it is still light-sensitive, and if not fixed, will eventually be destroyed by ambient lighting – but the formulation has such low light sensitivity, and there is so little ultraviolet present in my studio lighting, that we can examine it safely under “normal” indoor lighting for several minutes without too much damage.
The core chemical process of a daguerreotype is similar to traditional black-and-white photography, often called the “AgX process”, where “Ag” represents silver (from the French Argent, meaning “silver” and also “money”), and “X” represents some halogen, or a mixture of halogens, typically including chlorine, iodine, and bromine. We will discuss the chemistry in far more detail in later sections, but in essence, a daguerreotype begins as a mirror-like plate of silver metal. Although a solid sheet of silver would work perfectly well, cost considerations encourage using silver plated onto a substrate, usually copper metal or glass. Regardless of the substrate, it is exclusively the silver layer that undergoes the chemical reactions involved in producing an image, so we will focus on this layer at the moment. The metallic silver mirror destined to become a daguerreotype is exposed to a halogen in gas phase, such as iodine vapor, and the halogen reacts with the atoms of silver on the surface, converting them into silver iodide. This renders the plate light-sensitive, and it is subsequently exposed in-camera. During exposure, that silver halide is converted into atoms of atomic silver metal – little granules of silver – in accordance with the amount of light received. Areas with no light remain silver halide; areas with strong lighting see significant deposition of silver metal; areas with intermediate levels of lighting see an intermediate level of conversion. We then develop the daguerreotype in one of two ways. The traditional method is to expose the plate to mercury vapor, created by literally boiling mercury inside of a pot and holding the plate over the fumes. This mercury then forms an amalgam, essentially just an alloy – the word “amalgam” simply means “an alloy where one component is mercury” – with the silver granules in areas where the plate was exposed to light. Alternatively, we can apply what I describe as the band-gap method: although silver halides are normally only sensitive to ultraviolet and blue light, that is, to short, high-energy wavelengths below about 480 nano-meters, it turns out that, when a silver iodide crystal is located adjacent to atoms of metallic silver, it becomes sensitive to longer wavelengths of light, up to about 700 nano-meters.
3. The Plate-Silvering Box: Design & Construction
Hello, and welcome to the Daguerreotype Primer, by Free World Blues. Today, we will be discussing