When a pristine door handle is viewed it may be difficult to grasp just how much time and skill is devoted to cleaning and fine tuning the details of the casting before it is patinaed. This process takes hours and sometimes days and some of the steps are shown below.
In the lost wax method of casting wax replicas are “gated” and wax runners or rods are attached to the wax patterns at various points so that the molten bronze can flow through these connections and pass through the gates and fill the cavity of the shelled piece. Once cast, the runners that connect the individual castings are cut and the bronze can be recycled but a small gate end is left, and this is removed using a cut-off wheel on a hand held grinder.
The casting may contain tiny silica fragments that were left after the wax piece was shelled that need to be removed. A handheld metal burnisher with a flap wheel made of scotch brite and sand paper is used to remove shell fragments as well as scratches, blemishes and bubbles buried beneath the surface of the casting. When bronze is poured tiny pockets of air underneath the surface are sometimes created and are only seen once the casting is buffed when they show themselves as tiny dimples or voids. To fill the void a silicon bronze rod is melted with a TIG welder and drops of melted rod fill these voids.
Below left a grinder with coarse grade cut-off wheel. Below right a handheld burnisher with a medium coarse wheel flap and a green very coarse wheel flap.
While the burnisher is an extremely effective tool it takes a fine dremel to get into the veins and undercuts of a casting. The image here shows the tip of the dremel burr as it removes residual white shell from the leaf vein. A dremel is an invaluable tool for fine detail and a good one will come with several burrs, rasps and files. The dremel bits are made from tungsten carbide steel and fit into the dremel socket which when rotating at a high speed can cut and grind silicon bronze and even 316 stainless steel.
A fixed buffing machine with coarse and fine scotch brite disks is used to clean remaining marks or scratches. The casting is pushed into the path of the rotating disk which removes a small amount of the surface. A consistent and even pressure needs to be applied with the buffing disk to avoid unwanted grooves and directional marks.
