This section is from the American Hand Book of the Daguerreotype, by Samuel D. Humphrey. Published S. D. Humphrey, 37 Lispenard Street 1858.
The following process possesses some interest, and is worthy a trial from operators. M. Natterer, of Vienna, discovered a process for obtaining proofs on iodized plates with the chloride of sulphur, without the use of mercury. A plate of silver is iodized in the usual manner, and then placed on the top of a vessel six or eight inches high, having at the bottom, in a small cup, a few drops of chloride of sulphur; it should remain exposed to the action of the vapor until the sombre yellow color is changed to a red, after which it is brought to a focus m the camera, where it is exposed to the light in the camera, for about the time necessary to produce an ordinary daguerreotype. The plate is then taken out and examined in the camera by the light of a candle. It often occurs that no trace of the image is as yet perceptible, but if the plate is heated by placing over a spirit lamp the unprepared side, or if left for some time in the dark, or, lastly, if exposed only a few seconds to a weak, dimmed light, the positive picture then appears with all its shades. Of these three modes of bringing out the image, the second is superior to the others.