During the past ten years there has been a steady growth in the use of the reactive metals in jewelry and art. Within this group of metallic elements the most common are titanium and niobium. Titanium remains the most popular for commercial jewelry, followed by an expanding use of niobium. Niobium is both more ductile and more colorful. These metals can be cut, formed and finished with standard hand and power equipment. The high colorations can then be achieved through a simple anodizing process.
Note: In the following discussion of the techniques and processes for preparing and coloring these metals, titanium will be used as the reference metal with notes to any variation as they apply to niobium.
Note: All chemicals should be used under strictly controlled conditions. Hydrofluoric is an insidious acid and requires special handling equipment, safety precautions and disposal.
Both metals require lubrication when drilling and machining. The low thermal conductivity of titanium can cause heat to build and damage cutting tools. Use cutting oil or soapy water as a lubricant to lengthen tool life.
The colors produced appear in up to five repeating orders. Most of the current jewelry is produced with the first two orders. All the colors of the light spectrum are not produced. True red and forest green are not generated.
When the oxide is of a thickness to generate interference colors, its depth is measured in angstroms (Å=1/100,000,000 centimeter). This layer can vary in thickness from 500 to 1,000Å+ depending on the color. It is not the oxide itself that is perceived by the viewer but its effect on light.
Although harder than the parent metal, the extreme thinness of this oxide dictates that it is not a strong wearing surface. Bracelets, belt buckles, rings and items that normally receive heavy abrasion should not be considered unless the metals are protected by other design elements.
This is the type of coloration that most metalsmiths start with on titanium because no special equipment is necessary. At temperatures as low as 640 degrees F titanium will begin exhibit its first golden colors. Then, with increasing temperature and time, a variety of hues will appear. A torch or small kiln can be used.
Throughout the thermal coloring process cleanliness is an absolute necessity! Dirt, dust, oil and finger prints will discolor the oxide as it is growing. It is possible to contaminate the surface for special effects. Refinishing a piece that has discolored during the heating operation is difficult and time consuming. Niobium does not heat color. When heated to a dull red and held for 10-15 seconds it will produce a tough gray/black oxide. This is a very hard finish and works well in many applications where a black metal is desirable. The piece must be formed first because heating hardens the metal. The black oxide can be polished, waxed and even engraved and anodized.
Kiln coloring can be done in a standard enameling kiln. Running at temperatures between 800 and 1,200 degree F, a few minutes in the kiln will produce golds, purples and blues. Actual temperatures and times will relate to the size and thickness of the metal. Solid one color pieces can be produced with this method.
Reactive Metals Studio, Inc., ArtMetal, and the author assume no responsibility and disclaim all liability for injuries and /or damages and/or loss of profit from the use or attempted use of the processes described in the following paper.
About the author: Bill Seeley is president and founder of Reactive Metals Studio, Inc. He is considered an expert in this field with over fourteen years experience as artist, teacher and consultant. This excerpt was compiled from "Studio Preparation and Coloring of Titanium" Bill's Masters Thesis completed at the University of Kansas. If you have questions please feel free to call 800/876-3434 or FAX 520/634-6734.
Author: Bill Seeley
ArtMetal Editor/Curator: Enrique Vega