How to Cut Glass in a Straight Line or On a Curve

Whether setting a window pane, creating a stained glass mosaic, or cutting a jar for another project, cutting glass is a handy skill that isn't difficult to pick up. With the right tools and a steady hand, anyone can start cutting standard glass at home. Plus, we spoke with Glassblowing Expert Douglass Brown and the experts at Bicycle Glass to get handy tips on how to safely cut glass.

Using a Glass Cutter to Cut Glass

Line a flat work area with a towel or piece of cardboard.
Wipe down the piece of glass before you cut it.
Measure the glass and mark your score line.
Place a straight edge along your mark.
Add oil to the cutting wheel and hold the cutter like a pen.
Score the glass by rolling the cutting wheel along your mark.
Gently press along the score line to break the glass.

Section 1 of 6:

Cutting a Straight Line with a Glass Cutter

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1
Set up a flat work area with a soft surface. Choose a flat surface large enough to fit your piece of glass. Clean the area and then line it with something that’s slightly soft and won't scratch your glass, like a piece of cardboard, cork, or even a towel.^{[1]
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- Avoid working over the carpet so you don’t get glass shards on the floor if your piece of glass shatters.
- For their safety, keep pets and children away from your workspace and materials.
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Clean the glass surface where you plan to make cuts. Any grime or silica on the glass may ruin your score. Wipe these away by running a cloth or your finger along the surface of the glass where you plan to score.^{[2]
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- Use a household glass cleaner to get the glass extra clean.
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Measure and mark the desired score line. The experts at Bicycle Glass recommend measuring carefully and then marking the score line along the entire length of the glass because the score must run from one edge of the glass to the other to prevent breakage. Write on the glass with a marker (preferably with a straight edge if cutting a straight line). Or, mark your line on paper and place the glass on top of the paper.^{[3]
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- Keep lines under 2 feet (61 cm). Scores longer than 2 feet (61 cm) have a high failure rate when breaking.
- Make sure your marks leave about 6 inches (15 cm) of glass on each side to grip and break. If you cut smaller pieces, use special tools, like grozer pliers, to break off glass you can't get a hold of.
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Lay out a straight edge along the mark you made on the glass. Use a yardstick or a normal desk ruler with a thick enough profile that it won't catch on the cutting wheel. The cutting wheel is offset by about ⅛ inch (3 mm), so compensate for this as you line up your straight edge.^{[4]
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- Use tape to secure the straight edge to the glass so it doesn’t slip as you’re making the cut.
- If you don’t have a straight edge, place masking tape along the edge of your mark to help you gauge your cut.
5
Dip the glass cutter in cutting oil and grasp it like a pencil. The experts at Bicycle Glass say glass cutters are the most straightforward way to cut plate glass. Oiling the glass cutter with a cutting oil creates a smoother score line. ^{[5]
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- Glass cutters are about the size of a pencil and use a diamond or a hardened wheel to mark a score into the glass so it breaks cleanly along a line.
EXPERT TIP

Bicycle Glass
Glassblowing Experts
Bicycle Glass Co. was founded in 2016 by David Royce and Michael Boyd, two professional glass experts. Bicycle Glass is primarily a lighting company, committed to quality, sustainability, and affordability. All Bicycle Glass products are made of high-quality, recycled glass and are hand-blown by a dedicated team of artisans. The studio is committed to reducing its carbon footprint by conserving energy in all of its production. Using renewable wind energy to offset all electricity usage, the studio is actively working toward the goal of carbon neutrality. Bicycle Glass believes that high-quality, handmade glass products should be within reach for everyone.

Bicycle Glass
Glassblowing Experts

Using a glass cutter is the easiest way to cut glass. Commercially available glass cutters are great tools for DIY crafts. They score the glass, making clean breaks along the line. For perfect circles, use a circular glass cutter that scores a circle, making it easier to tap away the unwanted pieces.
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Use even pressure to roll the glass cutter’s wheel along your mark. Pull the cutter along the surface in one long motion, listening for a smooth sound like ripping silk. A gritty sound means that you’re using too much pressure or that you didn’t oil your cutter. The less sound you make, the cleaner your score will be.^{[6]
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- Aim to make a uniform score along the entire length of the glass. If you push too hard (a very common mistake), your cut gets "hot," meaning that it snaps and pops. This creates microscopic imperfections in your score, and the glass won’t break cleanly.
- Do not run back and forth over the line if you miss a spot.
- Wipe a little of the oil away to check that your score is barely visible.
- Carbide scribes and large nails are also capable of cutting a straight line in glass and can be handy if you don’t have a glass cutter. After cleaning and marking your glass, place a straight edge along your mark. Dip the tip of the scribe or nail in cutting oil. Then, hold the scribe or nail at a 45-degree angle as you score the glass using the mark and straight edge as a guide.
Videos made replacing windowpanes totally doable. "When my old window frames didn't fit new glass panes, I thought I'd never be able to DIY it. But these step-by-step clips gave me the know-how to measure, score, and cut the glass perfectly. Now, those antique windows are as good as new!" - Tory H.

First timer put at ease by safety reminders. "As a total beginner, I was freaked out trying to cut glass for the first time. But the clear pointers on technique plus blunt safety tips built up my confidence. Now I feel ready to rock this homemade project thanks to the super thorough guidance." - Dawn V.

A broken-down primer demystified everything. "With zero glass-cutting experience, this step-by-step walkthrough was invaluable. The graphics illustrating scoring angles, breaking techniques, and curve cutting were clutch for visuals. Now I get this intricate craft well enough to give it a shot!" - David S.

Inspired by a pro's flawless technique. "Watching a professional neatly measure, score, and cut a custom mirror pane was mesmerizing. Recalling that motivates me to carefully follow all the tips here to mimic that precision. This will help me copy that adept approach!" - Fiona M.

Exactly what I needed for a household project. "Needing to resize a small pane for a clock face, the direct instructions and diagrams were perfect. Now I know how to cut glass cleanly instead of living with jagged edges. This practical advice made my home craft possible." - Kevin K.

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Grasp each side of the cut carefully and apply light pressure. Wearing safety gloves, hold the glass as if you were trying to break a potato chip in half with two hands. Bicycle Glass recommends applying minor pressure from the wrist to break the glass along your score line. Simply twist your wrists (your right wrist will turn clockwise and your left will turn counterclockwise) without moving your elbow.
- Alternatively, place the glass so the score line is along the edge of a table. Use one hand to hold the glass against the table and the other to grasp the free edge. Applying gentle, even pressure, snap the glass.^{[7]
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- Brown also recommends putting a pencil underneath the glass along the score line and then pressing it down so you're creating a fulcrum point for the glass to snap along the score line.
- Using the tapper on the opposite end of your glass gutter to tap the backside of the glass along the line you scored before you try to snap it helps it break more easily.
- When the glass breaks, it may simply start as a "run." If it only runs an inch or so, apply a little more twisting pressure and it will continue to run.
- This method is also used to cut plexiglass.
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Use fine sandpaper or a glass grinding stone to remove the sharp edge. This edge was created along your score line and can be very sharp. Not only does smoothing glass edges reduces the chances of being cut, looks more professional, is less likely to chip along the edges, and has some added strength.^{[8]
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- The experts at Bicycle Glass recommend starting with a rougher grinding surface and moving to finer surfaces as you grind the glass.
- 80-grit grinding stones and sandpaper are a good place to start for the initial rough grinding. 400-grit and up are good for creating a smoother finish.

Section 2 of 6:

Cutting Glass on a Curve with a Glass Cutter

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1
Place your glass on a flat surface and draw the curve. Choose a flat surface that’s large enough for your piece of glass. Place a towel or piece of cardboard on the surface and put the glass on top to prevent scratches. Mark your lines with a marker or set your glass over your pattern.^{[9]
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- This method is frequently used for cutting stained glass.
- It’s also possible to cut glass with a circle cutter. A glass circle cutter has a suction cup that sticks to the glass with a scoring tip on an adjustable arm.
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Use your glass cutter freehand to score along the mark. Move your hand as smoothly as possible to keep the score even along the entire curve. This helps you make a clean break.^{[10]
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- To cut an inside curve, score a series of shallow arcs inside the one you just made. Make each arc increasingly deeper until you get close to your original cut.^{[11]
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- For a sharp outside curve, make a series of straight marks that start at different places on the curve and skew off at a tangent outside the piece all the way to the edge of the glass. These score marks look like sun rays coming off your curve.
- Use grozing pliers to remove the smaller pieces of glass until you reach the first cut you made. Place the edge of the grozer pliers along the edge of each score line and gently tug the smaller piece to remove it.^{[12]
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- Once you reach the first cut, use the pliers to “nibble” along the edge of the score line to remove even smaller sections of the glass.^{[13]
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Press your score from the glass’s backside to start a run. Follow the run with light pressure, watching the glass separate where you scored it. If your score is too close to the edge of a piece of glass, it may crack to the edge instead of along your score because that is the easiest path for the run to take.^{[14]
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- Make sure you break the glass along lines that run from edge to edge.
This machine is like a wet sander for glass that uses a spinning wheel with fine diamond chips as a grinder. Turn on the router and press your curve firmly against the grinder to smooth out your curve, then sand as normal.^{[15]
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EXPERT TIP

Bicycle Glass
Glassblowing Experts
Bicycle Glass Co. was founded in 2016 by David Royce and Michael Boyd, two professional glass experts. Bicycle Glass is primarily a lighting company, committed to quality, sustainability, and affordability. All Bicycle Glass products are made of high-quality, recycled glass and are hand-blown by a dedicated team of artisans. The studio is committed to reducing its carbon footprint by conserving energy in all of its production. Using renewable wind energy to offset all electricity usage, the studio is actively working toward the goal of carbon neutrality. Bicycle Glass believes that high-quality, handmade glass products should be within reach for everyone.

Bicycle Glass
Glassblowing Experts

Always prioritize safety when working with glass. Make sure to wear proper protective gear and carefully handle the glass. This applies to all processes, including holding, cutting, or polishing. Follow safety protocols to prevent accidents and achieve successful outcomes.

Section 3 of 6:

Cutting a Glass Bottle or Jar with Fire

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1
Wrap a piece of string around a jar several times. Cut a piece of cotton string about the length of your arm. Holding one end against the glass, wrap the string around the glass bottle or jar. Tie the two ends so the string stays on the jar but is loose enough to work it off.^{[16]
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- Don’t use wool or acrylic. Wool is mildly flame retardant, and acrylic yarn will melt instead of burn.
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Remove the string, soak it in acetone, and put it back on the jar. Gently work the string off the jar. Pour the acetone into a glass bowl and soak the string in it. Then, slide the string back onto the jar all the way to the cut line.^{[17]
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- Soaking the string in acetone helps it burn more evenly once it’s lit.
- Don’t use plastic or metal bowls for acetone.
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Hold the jar with pliers and light the string on fire. Use a pair of pliers to hold the jar near the lip. Then, use a lighter to light the string on fire. As the string burns, gently rotate the jar to help the fire spread evenly.^{[18]
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- Remember to wear protective gloves, goggles, and a mask to keep your skin, eyes, and lungs safe.
- Alternatively, Brown recommends hot popping a bottle to cut it. Score a line around the glass bottle. Then, spin it around using a record player or lazy susan while applying a butane torch to the score line.
4
Dunk the jar in a bucket of ice-cold water as the string burns out. Don’t wait for the fire to go out on its own. When you notice the string is nearly burned out, place it into a bucket of ice water. The sudden change in temperature causes the glass to break along the string, cutting the glass bottle or jar.^{[19]
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- The experts at Bicycle Glass recommend scoring the bottle or jar before attempting to cut it using heat. “There's no guarantee that method will always be successful. And a lot of it depends on how well the glass was sealed in the first place.”

Section 4 of 6:

Cutting Glass with a Dremel Tool

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Fitting your Dremel with a glass cutting wheel makes it easy to cut glass, especially if it’s rounded like a jar or bottle. Remember to clean the glass with a high-quality glass cleaner before you start to remove any dirt or debris.
Wrap your masking tape around the jar or bottle near where you’ll be making the cut. Try to keep the tape as smooth and straight as possible.^{[20]
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Brace the jar or bottle against something solid and mark your line. Brace the bottle along its length and bottom. Then, hold the tip of a pen or marker steadily against the surface of the tape. Roll the bottle so the marker makes a straight line on the tape around the bottle's circumference.^{[21]
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- Roll the bottle slowly to get the straightest line possible. This is your cutting line.
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Use the Dremel and cutting wheel under water to cut along the mark. Take the bottle to a sink and turn the faucet to a medium flow. Hold the bottle steady and place the edge of the cutting wheel along the mark. Try to keep the other edge of the cutting wheel in the running water as much as possible.^{[22]
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- It’s not necessary to keep the whole cutting wheel or the bottle in the water. Just skim the water along the most convenient edge of the wheel.
- Water helps the cutting wheel cut the glass more efficiently.
- Continue cutting around the bottle until you’ve moved around the entire circumference.
- Remember to wear protective gear to keep your eyes, lungs, and skin protected while cutting glass.
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Peel off the take and sand the cut edge if it’s still sharp. Use wet sandpaper or a diamond-tipped grinding bit to smooth the cut edge of the glass if necessary. Place the bit on the Dremel and wet the tip. Then, turn on the Dremel and run the bit lightly along the cut edge of the glass.^{[23]
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- Continue to run the bit over the cut edge until it’s rounded and smooth.

Section 5 of 6:

Cutting a Small Round Hole in Glass

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One of the easiest ways to cut a perfectly round hole in glass is to use a variable-speed drill with a carbide bit or diamond-tipped bit.
Apply 2 strips of masking or painter’s tape to make an X on the glass where the hole will be. Then, measure and mark the drilling spot.^{[24]
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Using a ⅛-inch (3 mm) diamond or carbide drill bit, place the drill on your mark. Apply light pressure at a low speed (about 400 rpm) until you create a small indentation in the glass.^{[25]
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Switch to the size of bit matching your desired hole size and drill. Apply a drop of cutting oil into the pilot hole if needed. Place the tip of the diamond or carbide drill bit in your pilot hold. Using a low speed, maintain light pressure to drill the hole.^{[26]
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- Stop every so often to clear away glass dust, and add more oil if necessary.
- Always use protective gloves, goggles, and a mask when drilling a hole in glass.

Section 6 of 6:

Frequently Asked Questions about Glass Cutting

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How do you make a homemade glass cutter? It’s possible to make a glass cutter out of a spark plug. Use a Dremel tool to cut the metal threads off the end of the spark plug to expose the ceramic end. Then, use the Dremel tool to grind the end of the ceramic to a fine point.^{[27]
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- Once you’ve ground the ceramic to a point, use it in the same way as a glass cutting tool.
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What materials will cut glass? Any stone that has a higher rating on the Mohs hardness scale than glass (5.5 - 7 Mohs) will cut it. For example, diamonds (10 Mohs) and quartz (7 Mohs) are capable of cutting glass.^{[28]
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Trustworthy Source

US National Park Service
Agency responsible for the maintenance and promotion of national parks and monuments

Go to source} Additionally, people also cut glass with tools made of tungsten carbide and hardened steel.
- Some believe it’s possible to cut glass with paper, but this is a myth.
- It may be possible to use boiling water to help cut a glass bottle. After scoring a line around the bottle, pour boiling water over the score line and then dunk the botting in cold water. However, this isn’t a reliable way to cut glass. If the boiling water runs past the area of the score line, it may warm the rest of the bottle, which causes it to shatter when placed in cold water.
- Razor blades are sometimes able to scratch glass, but they aren’t strong enough to make a score line.
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What are the notches on a glass cutter for? After you score the glass, the 3 grooves at the end of a glass cutter help you snap smaller slivers of glass off the edge of a larger piece. They’re helpful if the piece you’re cutting off is too narrow to snap along the score line using your hands or the edge of a table.^{[29]
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- After scoring, simply fit the edge of the glass into one of the notches and push the handle of the glass cutter toward the edge as leverage to break the glass along the score line.

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Question

How do you bend a glass?

Bicycle Glass
Glassblowing Experts
Bicycle Glass Co. was founded in 2016 by David Royce and Michael Boyd, two professional glass experts. Bicycle Glass is primarily a lighting company, committed to quality, sustainability, and affordability. All Bicycle Glass products are made of high-quality, recycled glass and are hand-blown by a dedicated team of artisans. The studio is committed to reducing its carbon footprint by conserving energy in all of its production. Using renewable wind energy to offset all electricity usage, the studio is actively working toward the goal of carbon neutrality. Bicycle Glass believes that high-quality, handmade glass products should be within reach for everyone.

Bicycle Glass

Glassblowing Experts

Expert Answer

Bending glass, particularly plate glass, a process commonly known as slumping, depends on the specific glass type and its intended use. This method doesn't require molten temperatures; instead, it hinges on reaching a temperature at which the glass attains the necessary malleability to bend and adopt different shapes. The precise temperature levels needed for the desired bends may differ, but this bending process is generally carried out in a kiln. The glass is gradually heated to a specific temperature and subsequently cooled to achieve the desired shape.

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Would a glass cutter cut mother-of-pearl tiles?

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You can cut any tiles you want with a glass-cutter. Just see it as a piece of glass, and when you've carried out the cut, place the handle of the glass-cutter exactly under the cut and press down firmly on both sides. The tile will break easily.

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Is cutting a mirror the same as glass, and why is using a lighter a good way to tell how old a mirror is?

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Yes, a mirror is just a piece of glass, but cutting it requires a first step. A mirror is reflective because of the silver color coating on one side. This requires you to first cut the coating with a razor blade exactly on the line where your glass cut is going to be. If you don't do this first, the coating will peel at your cut and ruin your mirror.

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Tips

Practice on scrap glass until you get the technique down before trying the real thing.

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If you do not achieve a proper scoring of the glass, do not go back over it with the glass cutter. This will damage the cutting wheel and is not likely not solve your problems.

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This method is best with common glass, also known as "double strength" (DS). These techniques can't be used to cut tempered glass, which will shatter when you try to break it.

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Warnings

Wear goggles to protect your eyes from glass chips, shards, and dust from cutting and grinding.

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If you apply a decent amount of pressure and nothing happens, stop. If the score is not sufficiently even, the glass may break at any point, including right into your hands.

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Wear gloves. Edges and points are very sharp, so wear a heavy cloth or leather glove that fits snugly so you don't lose your dexterity.

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Clean your work area thoroughly to remove any bits of glass you might have created. Even if you can't see them, they may become embedded in your feet or hands and hurt.

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