What is Anodizing?
Niobium and titanium react to exposure to oxygen by forming a clear oxide layer on their exposed surfaces. Anodizing causes this reaction to continue further than it would naturally, producing thicker layers of oxide. As the layer thickens, it begins to interrupt the light waves as they pass through and reflect off the metal surface. This interference creates color. Since the thickness of the oxide controls the color that is produced, and since anodizing controls the thickness, the color produced in a given jewelry piece becomes controllable through the anodizing process.
There are several ways to anodize a niobium or titanium workpiece. Using the bath anodizing process, you can create a single, solid color or you can create a rainbow effect or multiple solid-color blocks. Using the spot anodizing process, you can create ‘painted’ and patterned designs. Instructions for bath anodizing are below; to learn how to apply ‘painted’ or patterned designs, see our “How To Spot Anodize Niobium and Titanium” instructions.
Finish Your Jewelry Piece
To the greatest extent possible, complete all surface finishing on the jewelry piece before anodizing. The layer that is responsible for the color (the anodized layer) is comparatively thin, and it’s easy to remove it inadvertently in processes such as sanding and buffing. Creating a texture on the metal surface, or creating a ‘tooth,’ with Scotch-Brite™ pads or sandpaper before anodizing will cause the surface to reflect light a bit differently than if the surface were polished. A matte finish results in colors that are slightly less bright, but the color is less affected by the angle from which the jewelry is viewed because the uneven surface scatters the light rays over a wider area. A highly polished surface delivers brighter color but is more affected by the angle of viewing. Based on your design, you can play with how the light travels and reflects. Sanding or scratching in different directions can reflect the light differently, displaying a range of interesting effects. Before anodizing, make sure it is scrupulously clean—dirt, dust, oils and so on interfere with the anodizing process.
If you are working with titanium, you will need to take an additional cleaning step. The nature of the titanium oxide naturally present on its surface and the manufacturing processes that produce the metal require that it be more aggressively cleaned than niobium. We recommend using Multi-Etch®. This non-acid cleaner is extremely effective and safer for the environment than acids. Follow the manufacturer’s instructions carefully. This is not necessary if you are working with niobium.
Set up the Anodizing Bath
The anodizing bath is an electrolyte solution. We use TSP-PF granules, a phosphate-free soap that is environmentally friendly. Dissolved in pure water (distilled or demineralized), TSP-PF produces a non-foaming soapy solution rich in electrolytes, ideal for anodizing. Tap water almost invariably contains minerals that can cause defects in the oxide layer as it forms on the surface of the metal. Mix the electrolyte solution according to the manufacturer’s directions and pour it into a plastic or glass (non-conductive) container. The container must be large enough to accommodate the jewelry piece(s) and the cathode with a substantial space between them to eliminate the risk of their accidentally touching one another. Place a titanium or stainless steel cathode into the bath. Note: Because the anodizing process does not have much ‘throwing’ power, it is important that the cathode is as large or larger in surface area than the workpiece. If possible, shape the cathode so that it wraps around the interior of the container, surrounding the work piece. Place the protective plastic mesh between the cathode and the area of the container where the work piece will be submerged. It is important that the cathode and the anode (the work piece) do not touch since this will create a dangerous short in the electrical circuit.
Set up the SMT Micro Anodizer
Read the manual of the SMT Micro Anodizer and follow all safety and start-up procedures to ensure it is functioning properly before using it. Note: The anodizer carries up to 120 volts of electricity, and voltage that high is dangerous and can be fatal if not carefully and responsibly handled. Before plugging in the leads, turn the micro anodizer on and make sure the voltage is at 0. This is a good habit to get into when using the micro anodizer or any high-voltage equipment. With the anodizer OFF, connect the black (negative) lead to the cathode where it rises out of the electrolyte bath. Note: This is the reverse of the more familiar electroplating process, in which the red (positive) lead is connected to an anode (+) submerged in the solution and the black (negative) lead is connected to the work piece, so that the current flows to the work piece. In the anodizing process, the current flows from the work piece, so the leads are attached opposite to how they would be for a plating process. IMPORTANT! The alligator clip on the lead must NOT be submerged in the electrolyte bath. No metal other than the cathode and work piece must be allowed to come into contact with the electrolyte as it will prevent the process from taking place.
Prepare and Anodize the Workpiece
1. Attach the work piece to a titanium handling wire.
2. Put on rubber gloves.
3. Turn the anodizer on. Keep the current and voltage set to “0.”
4. Clip the red (positive) lead to the handling wire on the work piece.
5. Submerge the work piece into the electrolyte bath. Do NOT allow the alligator clip to come into contact with the bath.
6. Slowly, turn the voltage up until a predetermined setting is reached or until the desired color is achieved, then remove the work piece from the bath. The current generally remains at "0"; however, if the reaction is too slow, you can adjust the current up to speed the reaction.
7. Turn the voltage down to “0” and turn the anodizer off.
To create a rainbow effect, submerge the work piece in the bath. As you turn up the voltage, watch for the color effect to begin. Once it does, slowly lift the work piece out of the bath as you increase voltage. As the voltage rises, the portion of the work piece in the bath will change color while the portion out of the bath will remain the color it was when it left the bath. This creates a ‘rainbow’ effect.
Creating Multiple Solid Colors
To create multiple solid colors on a single work piece, use anodizing tape or a mask such as Mighty Mask keeps the electrolytic solution from touching certain areas of the piece while anodizing other areas. Begin by anodizing the areas that will require the highest voltage. Once a color has been achieved at a specific voltage, exposing the metal to lower voltages will not have any effect on that color.
1. Turn the metal over and lay flat, front side up. Make sure the surface is clean, dust- and dirt-free. Apply tape or a mask to all areas of your work piece except the areas that are to be anodized at the highest voltage in the design.
2. To apply tape, cut piece of tape the size and shape you want to keep from anodizing.
3. Start at one end of the metal and roll the tape on, working to prevent getting air trapped under the tape (similar to applying a protective screen to a cell phone or tint to a car window). Once the tape is applied to the surface, use a roller or burnisher to push out any air pockets. d) Now you can use an X-acto® or other fine-tip utility knife to cut away areas of the tape, exposing the areas to be anodized. Whatever is covered by the tape will remain gray in color. Note: Cutting the tape in this way will leave a sharp engraved line in the metal; if you do not want to have this line on the work piece, cut the tape on a clean glass surface and transfer the mask to the work piece in sections, burnishing each section carefully into place.
4. After masking, if desired, use Scotch-Brite™ or other abrasive to add texture to the exposed surface so that it will reflect the light differently.
5. With the anodizer off, clip the red (positive) lead to the work piece. Submerge the piece in the bath and anodize it.
6. Trim away the masking as desired for the color at the next highest voltage, checking to ensure that all edges of your mask remain sealed. Anodize. Continue until your design is complete.
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