Formulary's Hypo-Alum Sepia Toner yields sepia brown to reddish brown tones, that are slightly darker brown than the Sepia 221. The tone depends on the paper and length of time toned. Hypo Alum requires a hot water bath (125° F) and takes approximately 25 minutes to tone. The chemical action like other sepia toners is the conversion of silver to silver sulfide. This toner may be used for many years and improves with age. We recommend fiber based papers only with this toner.