Getting a glass project just right is painstaking work. You want that vase, pendant, or picture frame to mesmerize and shine.
Often, that means doing more than your initial glass working process. When you need to take that next step to complete the perfect project, it’s time to deploy coldworking techniques.
To get started, explore the most common methods of coldworking glass in this overview guide.
Definition of Coldworking
Coldworking is a broad and self-evident term. It’s about working with glass when it’s cold (vs. hot or warm). The term encompasses many different finishing techniques.
Interested in other ways to manipulate glass? Check out our beginner’s guide to glassworking.
When Coldworking Works Best
Do your coldworking after annealing glass. This controlled cooling process relieves internal stresses and improves durability.
To make sure you get annealing right, use a quality kiln with precise temperature control. Check out accurate, efficient Hot Shot glassworking kilns, for example.
The Many Different Ways to Finish Glass Projects
Most coldworking involves some form of refining your glass surface. You’re removing small bits of material to adjust the shape, create contour, smooth edges, etc. Here are the most common methods artisans use.
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Sandblasting is a versatile technique that can etch, carve, or add shadow, texture, or depth.
- A sandblasting kit with air compressor and nozzle
- Blasting media
- Sandblasting enclosure
- Dust mask and safety goggles
First, set out whatever pattern you want with a “resist” material such as vinyl strips or masking tape. Then use compressed air to blast the surface with a fine abrasive (aluminum oxide or silicon carbide).
Your blasting method can produce different effects. Continuous, uniform blasting creates a consistent texture. Blasting some sections more than others creates shadowing.
You can also use sandblasting to remove devitrification (a hazy imperfection). Or drill a hole by sandblasting at close range.
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Engraving makes small, precise cuts into the glass. Use it to create artwork or text on the surface.
Several different tools enable engraving:
- Pin vice with a diamond burr – Simple, low-cost method.
- Handheld rotary drill – Most common choice with a variety of burrs and abrasive accessories.
- Copper wheel on a lathe – Traditional method.
- Stipple with a carbide point – Most painstaking.
- Laser – Precise, expensive, expert-level technique.
Tools with different shapes and widths enable specific designs. Apply varied pressure with the tools to change the depth and intricacy of the engraving.
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Etching uses acidic chemicals—hydrofluoric acid—to eat away at glass. The result is an elegant frosted surface.
Surface etching is easy to do at home. But due to the caustic chemicals, protect your hands and work surfaces. You also need a space with good ventilation.
As with sandblasting, you create designs or text by applying a resist material to set off areas for etching. The resistance material can be as simple as cut masking tape or contact paper. Or use adhesive stencils from your local craft supplier.
Apply an etching cream, such as Armour Etch, with a paintbrush. Allow it to work its etching magic for a few minutes. Then wipe it clean.
It’s a fast way to create glass decorated with designs or text. Plus, the glass and its finish are dishwasher safe.
More intricate designs—such as varied shading and deeper carving—are possible. But these take greater skill.
The basics of cutting glass aren’t complex.
All you need is a well-oiled glass cutter. This pen-sized tool has a small wheel with a carbide or diamond edge.
Here’s a high-level overview of the process:
- Protect your work surface with cardboard or a towel.
- Mark off your cut. Any straight edge will do for straight lines. Trace stencils for shapes.
- Score the glass with the cutter. Then snap the glass along the scored line.
Some glass cutting applications are more intricate. But most will involve some kind of scoring. To cut a bottle, for example, you score the edge. Then heat up the glass and rapidly cool it until it snaps along the scored line.
Need to smooth out any imperfections? You may want to use our next technique ...
There are two main ways to grind glass and refine the shape of your workpiece:
- The hard way – by hand with a carbide grinding stone.
- The expensive way – with a wet grinder.
Either technique takes patience. Be sure to wear protective gear (gloves, safety glasses, dust mask).
The more grinding work you do, the more you’ll want to invest in the wet grinder. This equipment rotates a diamond-tipped wheel. One side has a wet sponge attached to a water reservoir. The wheel rotates against the sponge, helping keep the process cool.
To grind, hold your glass securely with two hands. Push your glass gently against the wheel in slow, controlled movements.
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Polishing is the more refined sibling of grinding. Use it when you want that beautiful, shiny finish.
The simplest way is to use a diamond polishing paste. This technique is ideal for removing scratches or achieving a mirror finish.
Apply this fine abrasive solution with a felt pad. Start with a thicker grit (6 micron), then move to finer grits to reach your desired look.
There’s also a technique called fire polishing. It involves grinding then firing the glass up to 1,325 °F, with a very brief soak. A fire polish is debatable as “coldworking” since it uses a kiln. But it’s a neat way to get a good gloss on your glass.
What You’ll Need for Coldworking
You can do a lot of glass cold working with a few basic tools and some more powerful equipment:
- Glass cutters – As discussed above. Available in different sizes and grips.
- Diamond files and diamond hand pads – For hand filing, sanding, and grinding.
- Handheld rotary drill or saw – For power drilling and cutting. Diamond blades and bits required for cutting glass.
- Vibrating lap – A distinctive glassworking tool that vibrates a silicon carbide platter at high speed to grind glass placed on top. Or use a cerium oxide platter for finer polishing.
- Wet grinder or belt sander – The glassworking version of the familiar belt sander takes a diamond-covered belt.
- Safety equipment – Goggles, dust mask, protective gloves.
Key Considerations When Coldworking
- Invest in quality. You might have noticed the word “diamond” several times in this article. Quality coldworking tools aren’t always cheap, but they’re worth it to help you get good results.
- Understand your abrasives. Coarser grits remove material quickly; finer grits provide a smoother finish. Progress through grits gradually for better results.
- Be patient. Precision takes practice. Take your time, and be prepared to make some mistakes. You can always grind down an imperfection.
- Watch out for thermal shock. Working with glass you’ve just fused? Allow your glass to equalize at room temperature before coldworking.
- Consider a follow-up anneal. How much stress have you put on your glass during coldworking? Depending on the intensity of the technique, you may want to anneal again to ensure a stronger product.
Display Your Finished Projects with Pride
When you’re done coldworking your glass creation, it’s time to recognize your accomplishment!
Admire and show off your work. Give it as gifts to friends and family. Maybe you’re ready to sell some pieces and start a side gig …
In any case, be sure to note what you learn with each coldworking experience, so that you can keep advancing your skills.