Historically, at the end of the process, the gelatin emulsion, having undergone a series of swelling and shrinking cycles as it passed from one processing solution to another, may have lost some of the hardness and physical strength it originally had, which could make it susceptible to scratching or damage. Also, some of the newly formed dyes in the emulsion needed to be further chemically protected against aging and light fading. Both of these tasks can be performed by treating the emulsion with a stabilizer, usually the last solution in a color process. However, through the use of modern forehardened emulsions and other chemical modifications, a number of newer processes have been reformulated to eliminate the need for an emulsion hardening agent in stabilizers.
Currently many processes are designed to save or eliminate water. "Washless minilab" processes are intended to provide processing for a customer in 1 hour or less, and may be located in department store, drugstore, or storefront locations not having sewers. Increasingly, such processes are also being found in professional and commercial photography houses. In these cases the stabilizer may also serve the function of a wash, by eliminating residual chemicals in the emulsion prior to the drying step, which is necessary for image stability upon long-term keeping.
Throughout much of the history of color films and papers, the most common and effective stabilizer was a water solution of formaldehyde, sometimes containing additional ingredients such as citric acid. However, in recent years, because of heightened medical concerns over the handling of formaldehyde plus its annoying lachrymatory odor, most processes today use alternative materials.
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