Etching is a popular artistic and decorative process used to create permanent patterns on the surface of the glass. The main methods are abrasive, acid, or lasered etching. Abrasive etching uses sandblasting equipment and an abrasive substance such as powdered garnet, which cuts through the glass at high speed. Acid etching uses hydrofluoric acid (HF) to dissolve metal salts (usually silver nitrate) out of the glass surface; other chemicals may be added to make a colored stain. Laser etching can be done with a range of different lasers, including CO2 and YAG lasers, depending on the type of material, laser power, and fluences that influence the depth of penetration.
Process:
The design for the image must be prepared to suit the method selected for etching. For acid etching, the graphic must be made by using either photographic or intaglio techniques, while abrasive or laser etching works well on line drawings such as pen and ink work. Lasered designs are often achieved by creating a computer file with all vectors (as opposed to rastered) or by engraving it. An abrasive method, sandblasting is the simplest and most economical way to etch glass. This method can be done in-home workshops with very simple tools, one of which is all that is needed. Glass powders are available to use as an abrasive agent, which is usually made up of aluminum oxide (corundum) – bonus.
A commonly used stencil material for acid etching is Mylar film because it resists corrosion from the acid during the process. Stencils typically have a thickness between 20-40 (.8 mils). Thicker stencils last longer but also require more force to remove them from the glass surface after completion of the etching process. For laser etching, a thin plastic or paper material is used as the stencil and can be easily removed with tweezers after ablating.
The most important step in creating an etched glass piece is to protect the surfaces of the glass that will not be etched. There are three ways to do this: covering them up, masking them with tape, or protecting them with resistance (also known as stop-off). Tape and/or stop-off materials should remain on the surface throughout the process and must be completely removed before firing.
Process Step By Step:
1) Clean your work area and all equipment before starting any project. Once you start, don’t leave it until you finish because acids take time to etch glass, and you want the acid bath to be fresh.
2) Design your project; choose a pre-drawn stencil, draw it yourself, or use an original drawing (Photograph).
3) Prepare a work table by placing a sheet of glass on top of a flat, clean surface. Draw design, letters, or words with a permanent marker.
4) Place stencil face down onto glass so that all markers are facing up toward you. Tape the edges of the stencil to the glass for extra stability if necessary. If using stop-off spray paint around the edge about 1/8″ wide, then wipe off any excess with a paper towel leaving only enough to protect the area not intended to be etched.
5) Pour about an inch of etching cream into a plastic or glass container that is larger than your workpiece. The depth of the acid should only cover the stencils, not touching the edges of the glass.
6) Float your workpiece in acid for 30 minutes to 1 hour, depending on how deep you want it etched.
7) Remove the stencil, tape, and stop-off material while wearing safety glasses and rubber gloves. Wash off any residue from etching cream with a water hose or spray bottle being careful not to get any on areas you don’t want etching. Rinse thoroughly until all residue has been removed completely.
8) Begin firing process using electric kiln (or small torch if working with glass beads). Use high temperature and hold for several hours.
In conclusion,
etching techniques are easy to learn but difficult to master. The design of the glass is what draws attention. When executed correctly, it can produce beautiful decorative pieces; when done wrong, it can make you want to throw the piece away. Remember that mistakes happen, and there is always an opportunity to re-fire your product with something else! Have fun creating works of art out of ordinary glass products.