This type of developing box is usually described as the European pattern. It consists of a wooden box in the top of which is a recess for the exposed plate, at the bottom of the box a dish of mercury rests in an iron recess. Outside the box a small spirit burner is used to heat the mercury.

The plate is held at an angle so that the development can be observed by holding a candle near the yellow side window. Often a thermometer is fitted to the front of the box with its bulb in the mercury. A set of nested frames would have been provided for smaller size plates. Common variations are to include a full width door to the front of the box, others have the area behind the plate is cut away diagonally.

Another form, described as the 'American pattern' was simpler, consisting of an inverted pyramid attached to a metal stand. The plate is placed horizontally on the top of the pyramid.

Knight's catalogue of 1853 shows a similar box to this example described as the 'Improved Mercury Box', however it is fitted with a slide to view the plate rather than a hinged flap. The cost was £1.9.0 for a model without a thermometer. Also shown is a model where the exposed plate is attached to the slanted lid of the box, the lid has to be raised to see the progress of development (this is also illustrated in the 'Barger, White, Daguerreotype' book). A further type where the plate is held vertically is shown and described as by Bingham (presumably R.J. Bingham). In Willats's 'Practical Hints' a box is illustrated able to take two or more plates next to each other, the plate holders rest against the outside of the box and have short handles attached to lift them.

The use of a developing box is described in Willats's Practical Hints on the Daguerreotype Process - "Into the cup at the bottom of the mercury-box put four or five ounces of mercury, which must be pure and free from moisture. ... The vapour of the mercury is raised by the application of a spirit-lamp to the cup which holds the mercury. When a thermometer is attached to the mercury-box, a temperature of about 160 degrees will raise the vapour of the mercury; if the box have no thermometer, the cup may be heated until the mercury is quite warm to the finger. If the mercury cup is removed from the box in order to its being heated, it is well after the operation to wipe the outside, on which a slight steam from the spirit may have settled. When the due heat is obtained it is better to withdraw the lamp before putting in the picture, which might, from a sudden jerk, receive spots by the splashing up of the mercury. The plate must remain till the picture is perfectly developed. Its progress may be observed by the light of a candle through the yellow glass in the front of the box. ... The plate is generally placed over the mercury box at an angle of 45 degrees for the convenience of inspection, but this is not necessary, and the plate may be placed horizontally or vertically, without disadvantage. ... It generally takes eight to fifteen minutes, or even longer, to perfect the operation; if however, no outline is visible in about three minutes, either the mercury has not been sufficiently heated, or the picture has been removed too soon from the influence of light in the camera. If the former case, the mercury may be again gently heated; but if made too hot, the plate will become covered with small white spots. The details are usually much better developed when the picture has been brought out slowly, and with a moderate degree of heat. ... The picture should remain in the box till the darker parts are well developed, which may be increased at the last moment till the picture is perfectly distinct."