Dell loves working with bronze, however, the process is expensive, exacting and labour-intensive. Below is a description of Dell’s methods which illustrates the painstaking nature of this breathtaking art.
The clay original is modelled, usually without being fired. When the clay is damp but firm (called leather hard) it is dropped off at the foundry to make a flexible (rubber) mould. This process is expensive, especially for large pieces as rubber is very expensive.
Flexible moulds have an outer casing made of fibreglass or plaster of Paris to hold the rubber in place. The original is then discarded. The mould is in effect the negative of the original (positive). Melted wax is then poured into the mould and with great skill, borne of experience, the foundry manages to get the 4/5mm closest to the rubber to set...and pours the rest of the wax back out. When the wax fully cools and is de-moulded (taken out of the mould), you are left with a hollow wax duplicate of the original.
Pins are pushed through the wax at strategic points. The pins protrude an inch or more outside and inside the hollow wax positive (duplicate of original positive.) The inside of the hollow wax is then filled with ceramic slurry, which hardens to become the ceramic 'core' for the bronze casting. The wax is also covered on the outside, layer by layer with a similar ceramic material, until it is thick enough (this varies according to the size of the bronze to be cast). This is called the ceramic shell.
The pins hold the core and shell together at a fixed distance from each other once the wax is melted out. The wax is melted away at the same time as the shell and core are baked hard in a furnace. The ceramic is then buried in a box filled with sand with an opening at the top to pour the molten bronze in and other holes allow air to escape as the bronze is poured in to fill the space where the wax once was.
When the bronze has fully cooled, the ceramic is removed from the sand, the inner core and shell are hammer drilled out and the brand new bronze is cleaned. Very exciting! The bronze is then cleaned up using angle grinders, files, dremmels, and sandpaper. Finally it is fully sand blasted for smoothness. It cannot be touched with bare hands after this point as human skin contains an acid which affects the patina (final colour).
The bronze is heated by blowtorch and then the patina (usually a mixture of chemicals) is sprayed on and rubbed back with an abrasive cloth until the desired colour is achieved. Finally, before the bronze fully cools, a wax is applied to protect the patina and bronze from natural oxidation. Eventually oxidation occurs and the wax disappears completely, leaving the typical appearance of bronze sculpture.