Every piece you create is an investment. It’s an investment of your time, your creative vision, and your hard-earned money for materials. The last thing you want is for that investment to be compromised by a hidden flaw that causes it to crack weeks or even months after it leaves the kiln. This is the risk you take when you mix incompatible glass. Learning the rules of Bullseye compatible 90 glass isn’t just about following technical guidelines; it’s about protecting your work. It’s the best insurance you can have to ensure every piece is as structurally sound as it is beautiful.

Key Takeaways

• Focus on the System, Not Just the COE: The COE 90 number is a helpful guide, but true compatibility comes from using products engineered to work together. Sticking with the complete Bullseye system for a project removes the guesswork and risk of stress fractures.
• When in Doubt, Test It Out: If you must mix Bullseye with another brand—even one also labeled COE 90—the only way to be certain they’ll work together is to perform a compatibility test. A small strip test can save you from the heartbreak of a large project cracking later.
• Technique is as Critical as Your Materials: Even perfectly compatible glass needs proper handling to shine. For a strong, flawless finish, always start with clean glass, follow the correct firing and annealing schedules for your project’s thickness, and use a shelf separator.

Your Guide to Bullseye Glass & Why Compatibility Matters

If you’ve spent any time in the world of glass fusing, you’ve definitely heard the name Bullseye. It’s a go-to brand for artists for a reason: consistency and quality. But what makes it so special, and why is everyone so focused on compatibility? Think of it like baking: you can’t just swap ingredients and expect the same result. Glass is a science, and understanding a few key principles will save you from the heartbreak of a cracked project after hours of work.

The most important concept to grasp is compatibility. When you heat and cool glass, it expands and contracts. If two pieces of glass expand and contract at different rates, they create stress against each other, which often leads to cracks. This isn’t just a surface-level issue; this internal stress can cause a piece to break days, weeks, or even months after it comes out of the kiln. Bullseye has spent decades perfecting a system of glass where every single product is tested to work with every other product in their line. This takes the guesswork out of your projects, letting you focus on creativity instead of chemistry. It’s about building a piece on a solid, reliable foundation so your artistic vision can truly shine.

What Makes Bullseye Glass a Studio Favorite?

At its core, Bullseye glass is a type of soda-lime glass, but it’s been specifically engineered for artists. Unlike the glass in your windows, every sheet of Bullseye is formulated for kilnforming, fusing, and kilncasting. This means it’s designed to be melted and shaped in a kiln without losing its integrity or color. The company is known for its rigorous testing and quality control, which is why so many artists trust it for their most important pieces. When you buy Bullseye, you’re getting a product that’s been tested to perform reliably, from its vibrant colors to its predictable melting behavior. This consistency is what allows you to create complex, layered designs with confidence.

Why Fusing Success Starts with Compatible Glass

Here’s a common misconception: if two pieces of glass have the same COE (Coefficient of Expansion), they must be compatible. Unfortunately, it’s not that simple. COE is a critical factor, but it doesn’t tell the whole story. Bullseye tests all its fusible glasses to ensure they “fit” together perfectly through the entire heating and cooling cycle. This internal testing is what makes their system so reliable. If you want to mix Bullseye with another brand—even one that claims to be COE90 glass—you absolutely must test them yourself first. Relying on the COE number alone is a gamble that can lead to stress fractures and ruined projects down the line.

Bullseye vs. The Rest: A Quick Comparison

Because compatibility is so complex, the safest rule of thumb is to stick with one brand per project. Bullseye only guarantees its glass will work well with other Bullseye fusible products. Mixing different brands, even if they share a COE of 90, can introduce variables that cause your project to fail. A classic example is trying to fuse Bullseye (COE 90) with System 96 glass (COE 96). The difference in their expansion rates is too great, and the piece will almost certainly crack as it cools. By committing to the Bullseye system for a project, you eliminate one of the biggest risks in glass fusing and set yourself up for a successful, beautiful result.

Key Differences: Bullseye (COE 90) vs. System 96 (COE 96)

Let’s get straight to the point. The biggest difference between Bullseye (COE 90) and System 96 glass is right there in the name: their Coefficient of Expansion. This number tells you how much the glass expands when heated and shrinks when cooled. Because COE 90 and COE 96 glass expand and contract at different rates, they simply can’t be fused together in the same project. Trying to mix them is a recipe for disaster, creating internal stress that will almost certainly cause your piece to crack as it cools in the kiln. This is why it’s so important to stick to one system for a project. You’re not just matching a number; you’re using a family of materials designed for harmony, ensuring your beautiful creation remains strong and intact long after it leaves the kiln.

Let’s Talk COE: Understanding Glass Compatibility

If you’ve spent any time in the world of glass fusing, you’ve heard the term “COE.” It’s often treated as the golden rule of compatibility—the one number you need to know to prevent your projects from cracking in the kiln. And while it’s absolutely a critical piece of the puzzle, the idea that you can just match up COE numbers and call it a day is a common misunderstanding. True glass compatibility is a bit more nuanced than that.

The science behind why some glasses play nicely together while others self-destruct is all about how they handle heat. When you fuse glass, you’re taking it on a wild ride of extreme temperature changes. Every piece in your design needs to expand and contract at a compatible rate throughout that entire journey. Understanding what COE really means—and what it doesn’t mean—is the first step to creating strong, stable, and beautiful fused glass art that will last a lifetime.

Breaking Down the Coefficient of Expansion (COE)

Let’s get the technical definition out of the way. The Coefficient of Expansion (COE) is a measurement of how much a material expands when it’s heated and contracts when it cools. In glass fusing, every piece in your project needs to have a compatible COE. If they don’t, they’ll pull apart from each other as they cool, creating internal stress that leads to cracks.

However, a common misunderstanding about glass compatibility is that it’s solely a function of this single number. While the COE value gives you a starting point, it doesn’t tell the whole story. Two glasses can be labeled “COE 90” but behave very differently throughout the heating and cooling cycle, making them incompatible in practice.

How COE Impacts Your Finished Artwork

So, why do we care so much about this number? Because ignoring it is a recipe for disaster. When you fuse glasses with incompatible COEs, you create a piece with built-in stress. As the piece cools, the glass with the higher COE will shrink more than the glass with the lower COE. This internal tug-of-war can cause your project to crack, sometimes immediately in the kiln, and sometimes days or even weeks later.

This is why it’s so important to use a system of tested-compatible COE90 glass for your projects. If you ever want to mix glass from a different manufacturer with Bullseye—even if it’s also labeled COE 90—you absolutely must test them yourself first.

What “Bullseye Compatible 90 Glass” Really Means

When you see “COE 90” on a piece of Bullseye glass, it means more than just a number. It represents a standard of compatibility. Bullseye has engineered its entire line of fusible products—from sheet glass to frit to stringers—to work together seamlessly. In fact, Bullseye glass is guaranteed to stay compatible through three full fuse firings, up to 1500°F.

This rigorous testing and quality control is what makes the Bullseye system so reliable. It removes the guesswork and the need to test for compatibility within their product line. You can confidently combine any Bullseye-branded fusible glass, knowing it has been designed to expand and contract in harmony. This standard is the reason artists trust Bullseye for complex projects.

Understanding Bullseye Glass Properties

Beyond the crucial concept of compatibility, getting to know the specific properties of Bullseye glass will help you predict how it will behave in the kiln and achieve the exact results you’re aiming for. Think of it as learning the personality of your materials. Understanding the different grades, how the glass flows when heated, and even its inherent quirks like bubbles will make you a more confident and skilled artist. These details are what separate good results from great ones, allowing you to plan your projects with precision and troubleshoot any issues that arise. Let’s look at a few key properties that every Bullseye glass artist should know.

Grades of Bullseye Glass: Fusible, Standard, and Curious

Not all Bullseye glass is created equal, and it’s important to grab the right type for your project. The main category you’ll work with for kilnforming is “Fusible” glass, also known as F-grade. This is the glass that has been tested for compatibility and is designed for fusing. Then there’s “Standard” or P-grade glass, which is not fusible and is intended for cold applications like traditional stained glass work. Finally, you might come across “Curious” glass. This is Bullseye’s line of discounted sheets that have minor imperfections in color or appearance but are still perfectly usable. They come in fusible (B-grade) and non-fusible (C-grade) options, offering a great way to experiment without breaking the bank.

The 6-Millimeter Rule for Full Fusing

Here’s a simple but powerful rule of thumb for fusing: when heated to a full fuse temperature, Bullseye glass naturally wants to settle at a thickness of about 6 millimeters (roughly ¼ inch). If you start with a single 3mm sheet, it will shrink and pull in on itself as it melts to achieve this thickness. To create a flat, stable, and even piece like a coaster or the base for a plate, you should always start with two layers of 3mm glass stacked together. This 6mm starting point ensures your project holds its shape and size, which is especially important when working with molds that require a specific volume of glass to fill properly.

Types of Clear Glass: Tekta vs. Crystal Clear

Bullseye offers two main types of clear sheet glass, and choosing the right one depends on your project’s needs. The standard is Tekta Clear, a versatile and reliable clear that works beautifully for most applications. However, if you’re creating a piece where absolute, water-like clarity is essential, especially in thicker projects or those with many layers, you’ll want to use Tekta Crystal Clear. As the name suggests, it’s an exceptionally clear glass that minimizes any tint, making it the premium choice when you want the colors beneath it to pop without any distortion. For delicate jewelry or thick cast pieces, Crystal Clear is often worth the investment.

Why Bubbles Are a Natural Feature of Handmade Glass

Finding tiny bubbles in your glass can be alarming at first, but it’s important to know that they are a natural and expected characteristic of all handmade sheet glass. Unlike machine-made float glass, the process of creating art glass introduces small air pockets. While Bullseye has perfected its process to minimize them, you can never eliminate them entirely. Instead of seeing them as flaws, many artists learn to work with them. You can learn techniques to control where bubbles form or even incorporate them as a design element. According to Bullseye’s own resources, understanding and managing bubbles is simply part of the craft of working with this beautiful, handmade material.

Don’t Guess: How to Test Glass Compatibility

So, you have a piece of Bullseye glass and another piece from a different company, both labeled COE 90. It should be fine to fuse them together, right? Not so fast. While it’s tempting to trust the numbers, the only way to be absolutely sure two different types of glass will play nicely in the kiln is to test them yourself. Think of it as a small investment of time that can save a larger, more intricate project from cracking under pressure.

Relying on COE numbers alone is one of the most common mistakes artists make. As the experts at Bullseye Glass often say, you must test if you plan to mix their glass with another brand. This simple step gives you the confidence that your finished piece will be strong and stable for years to come, without the hidden stress that can lead to a sudden break.

Your Step-by-Step Compatibility Test

The most reliable way to check for compatibility is with a strip test. It’s straightforward and doesn’t require much glass. Start by cutting two small, identical strips of the glasses you want to test, about 1 inch by 4 inches. Clean them thoroughly, stack one on top of the other, and place them on a prepared kiln shelf. Fire them using a full fuse schedule in your kiln.

After the firing and proper annealing, take a close look at your fused strip. A perfectly compatible pair will result in a straight, flat piece. If the strip has a slight curve or “C” shape, the glasses are not compatible. The direction of the curve even tells you which glass has the higher COE.

Alternative Method: The Polarizing Film Test

If interpreting a slight curve in a glass strip feels a bit like reading tea leaves, there’s a more visual method you can try: the polarizing film test. This technique allows you to see the stress between two different glasses with your own eyes. The process starts the same way as a strip test: you’ll need to fuse a small piece of your known glass (Bullseye) to a small piece of the glass you want to test. Once the piece has been fired and fully cooled, you’ll place it between two special polarizing filters and hold it up to a bright light source. What you’re looking for is a halo. If the two glasses are incompatible, you will see a distinct ring of light around the unknown glass where it meets the Bullseye glass. This bright line is a direct visualization of the stress between the two pieces. If you don’t see a halo, the glasses are compatible and safe to use together in a larger project. This test is a fantastic way to get a clear, undeniable answer and reinforces the importance of verifying glass compatibility before committing to a full-scale design.

Reading the Red Flags: Signs of Incompatible Glass

The curve in a test strip is the clearest sign of incompatibility, but there are other red flags to watch for. After firing, examine the seam where the two glasses meet. You might see fine, silvery lines or small, radiating cracks, which are tell-tale signs of stress. This internal tension might not cause a full break right away, but it creates a weak point in the glass.

Sometimes, incompatibility is subtle and doesn’t show up immediately. A piece might look perfect coming out of the kiln, only to develop a crack weeks or even months later. This delayed reaction is caused by thermal stress that slowly builds until the glass fails. Performing a compatibility test helps you avoid this kind of heartbreaking surprise.

Why a Matching COE Number Isn’t a Guarantee

Here’s the thing: COE, or the coefficient of expansion, only measures how much glass expands and contracts with temperature changes. It’s a critical number, but it doesn’t tell the whole story. Bullseye glass is engineered to be more than just a number; it’s a complete system. As Bullseye states, their glass is not simply “COE 90.” Other properties, like viscosity (how glass flows when hot), also affect how glasses fuse together.

This is why mixing different brands, even those with a matching COE, can be risky. Another company’s COE90 glass might have a different viscosity or chemical makeup, leading to internal stress when fused with Bullseye. For guaranteed success, the safest bet is always to fuse Bullseye glass with other Bullseye products.

Can You Mix Glass Brands? The Real Rules

When you’re building your glass collection, it’s tempting to mix and match beautiful colors from different brands. But when it comes to fusing, mixing brands is a risky business, even if they’re all labeled with the same COE. Think of it like baking: two brands of flour might not behave identically in a recipe. Each glass manufacturer has its own unique chemical formula, and these subtle differences can cause stress and cracks in the kiln. To save yourself the heartache of a failed project, it’s best to understand the compatibility rules before you start. Let’s break down what you need to know about mixing Bullseye with other glass brands.

Can You Mix Bullseye with Other COE 90 Glass?

This is a common question, and the answer is a firm maybe. While Bullseye is known for its COE90 glass, that number alone doesn’t guarantee it will play nicely with another manufacturer’s glass. Bullseye rigorously tests its own products to fuse together perfectly, but they can’t make that promise for another company’s glass. The only way to be certain is to test it yourself. Fuse a small piece of the new glass with a piece of Bullseye and check for any signs of stress after it cools. It’s an extra step, but it’s far better than risking an entire project.

What About Frits, Powders, and Stringers?

Just like their sheet glass, Bullseye frits and stringers are formulated to work seamlessly with other Bullseye products as part of a tested system. So, can you use another brand’s COE 90 frit on a Bullseye base? You could, but it’s not recommended since compatibility isn’t guaranteed. This could introduce stress into your piece that causes it to fail later on. For the most reliable results, stick with Bullseye frits and stringers when working with Bullseye sheet glass. This ensures every element in your project is fully compatible.

Why Sticking with Bullseye is the Safest Bet

One of the biggest advantages of committing to the Bullseye system is the peace of mind it offers. Bullseye provides a “Bullseye-to-Bullseye Guarantee,” promising their glass will remain compatible through three full fuse firings up to 1500°F. This is a huge deal for artists creating complex pieces that require multiple trips to the kiln. This guarantee means you can confidently layer and combine any Bullseye glass without worrying about hidden stress or delayed cracking. It removes the guesswork, allowing you to focus on your creativity, knowing your materials will work together flawlessly.

Fusing Gone Wrong: The Dangers of Incompatibility

We’ve all been there—you pull a piece from the kiln, holding your breath, only to find a crack spiderwebbing across your beautiful design. It’s one of the most frustrating moments for a glass artist. Often, the culprit is incompatible glass. When you fuse glasses that don’t expand and contract at the same rate, you’re creating internal stress that can tear your project apart. This isn’t just about aesthetics; it’s about the structural integrity of your art. Understanding what happens when you mix incompatible glass is the first step to preventing this kind of disappointment and ensuring your finished pieces are strong, stable, and last a lifetime.

How Incompatibility Leads to Cracks (Even Days Later)

The most common result of fusing incompatible glass is stress fractures. When two pieces of glass with different COEs are fused, they melt together just fine. The problem starts when they cool. The glass with the higher COE will shrink more than the glass with the lower COE, creating a powerful internal tug-of-war. This tension builds within the glass until it can’t take it anymore, and crack! A fracture appears.

Even if your project survives the initial cooling, it’s not out of the woods. These internal stresses can linger for days, weeks, or even years, acting like a ticking time bomb. A slight temperature change or a minor bump could be all it takes to cause a delayed crack. That’s why sticking with a tested, compatible system like Bullseye’s COE90 glass is so important for creating durable work.

What is Thermal Shock and How Can You Avoid It?

Thermal shock is what happens when glass breaks due to a rapid change in temperature. Fusing incompatible glasses makes your work extremely vulnerable to it. Because the different glasses are constantly pulling on each other, the piece is already under a huge amount of internal stress. It doesn’t have the strength to handle additional strain from temperature fluctuations.

Think of it like a tightly wound rubber band—it’s already so tense that the slightest nudge can make it snap. A piece made with mismatched glass might look fine in your studio, but moving it to a cold windowsill or washing it with warm water could cause it to shatter. Proper annealing in your kiln helps relieve some stress, but it can’t fix the fundamental problem of incompatibility. The only real solution is to use glasses that are designed to work together from the start.

The Slow Burn: Why Mismatched Glass Eventually Fails

One of the trickiest things about glass incompatibility is that the failure isn’t always immediate. You might fuse a beautiful piece using different brands of COE 90 glass and think you got away with it because it came out of the kiln looking perfect. Unfortunately, the piece is likely living on borrowed time. The internal stress from the mismatched expansion rates is always there, silently waiting.

Over time, everyday environmental changes can cause the glass to finally give in. This is especially heartbreaking if you’ve sold the piece or given it as a gift. The last thing you want is for your beautiful creation to crack long after it has left your studio. Using compatible glass, especially when working with intricate molds that can introduce their own stress points, is your best insurance against long-term failure.

What is Devitrification and How Can You Fix It?

Devitrification, or “devit,” is that frustrating, hazy film that can sometimes appear on your glass after firing, dulling its glossy finish. It’s essentially crystallization forming on the surface, and it can happen for a few reasons. The most common culprits are contaminants like dust or fingerprints, high humidity in your studio, or a firing schedule that holds the glass at a high temperature for too long. The good news is that it’s often preventable and sometimes fixable. The best defense is a good offense: always start with meticulously clean glass and use a reliable firing schedule for your kiln. If you do end up with devit, you can sometimes fix it by sandblasting the surface and re-firing, or by capping the piece with a layer of clear glass and firing it again to restore that beautiful shine.

Are You Making These Bullseye Glass Mistakes?

We’ve all been there—you pull a piece from the kiln only to find an unexpected crack or a cloudy finish. It’s a frustrating moment, but often, the cause is a simple, avoidable mistake. Learning to spot these common pitfalls is one of the best things you can do to get consistent, beautiful results with your glass. Think of it as saving yourself future heartache, time, and materials. Let’s walk through a few of the most frequent missteps so you can keep them from happening in your studio. By being mindful of these details, you set every project up for success before the kiln door even closes.

Mixing Brands Without Testing First

It can be tempting to mix and match glass from your scrap bin, but when it comes to fusing, brand loyalty pays off. Bullseye glass is specifically formulated and tested to work perfectly with other Bullseye COE 90 glass. While another brand might also be labeled “COE 90,” its chemical makeup and viscosity when molten can be different enough to cause stress and cracking. To avoid disappointment, the safest rule is to keep your project all in the family. If you absolutely must mix brands, a thorough compatibility test is essential, but for guaranteed results, stick with Bullseye-on-Bullseye. It’s the simplest way to ensure your finished piece will be strong and stable.

Assuming Any COE 90 Glass Will Work

This is probably the biggest misconception in the world of glass fusing. The term “COE 90” is a helpful guideline, but it isn’t the whole story. The Coefficient of Expansion (COE) only measures how much glass expands and contracts with temperature changes. However, true compatibility also involves factors like viscosity and chemistry. Bullseye has invested decades into creating a system where every sheet, frit, and stringer is a perfect match. As Bullseye themselves explain, a simple COE number doesn’t guarantee compatibility. Thinking of Bullseye as its own complete system, rather than just another COE 90 glass, will help you create pieces that last a lifetime without hidden stress.

Forgetting to Properly Clean Your Glass

A clean start is critical for a flawless finish. Dust, fingerprints, and oils from your skin can cause hazy spots, bubbles, or devitrification (a scummy, crystalline layer) on the surface of your glass during firing. Before you assemble your project, give every piece a thorough cleaning with a good glass cleaner and a lint-free cloth. Don’t forget about your kiln shelf, either. Applying a fresh, even coat of kiln wash or laying down a new piece of shelf paper prevents the glass from sticking. Taking just a few extra minutes for prep work ensures that what you see before firing is what you get when you open the kiln later.

Rushing with a Single Fuse-and-Slump Firing

Fusing and slumping are two different processes that require two different firing schedules. Fusing happens at a higher temperature to melt the glass pieces together into a single flat slab. Slumping happens at a lower temperature, allowing that slab to soften and gently bend into a mold. If you try to do both at once, you’re asking for trouble. The glass will likely get too hot and liquid, losing its shape and detail as it pools into the mold instead of gently draping over it. For the best results, always fuse your project flat first. After it has cooled completely, place it on a prepared mold and run a separate, lower-temperature slumping schedule.

Tips for a Perfect Fuse with Bullseye Glass

Working with Bullseye glass is a dream because of its reliability, but achieving that flawless, professional finish still comes down to good technique. Think of these tips as your foundational checklist for every project. Getting these steps right will save you from frustrating cracks, unwanted textures, and pieces that just don’t last. From the moment you pick up a sheet of glass to the final cool-down in the kiln, a little extra care goes a long way. Let’s walk through the essentials for getting a perfect fuse every single time.

Start with Squeaky-Clean Glass

This might seem basic, but it’s the most important first step. Always clean your glass before it goes into the kiln. Oils from your fingers, dust, or marker residue can cause hazy spots or devitrification—that dreaded crusty, scaly texture on the surface of your glass. A simple wash with warm, soapy water and a thorough rinse is often all you need. Make sure it’s completely dry before you start assembling. Taking a few minutes to properly clean your COE90 glass ensures that the final piece is crystal clear and exactly as you envisioned it.

Cleaning Products to Avoid Before Firing

While you might be tempted to grab any old window cleaner, not all cleaning products are suitable for fusible glass. Many common household cleaners, especially those containing ammonia, detergents, or denatured alcohol, can leave behind a thin, invisible film. When you fire the glass, this residue can burn onto the surface, causing the very devitrification or hazy spots you were trying to prevent. It’s a frustrating outcome when you thought you were doing everything right. For the best results, stick to a cleaner specifically designed for art glass or a simple solution of soap and water, followed by a thorough rinse and drying with a lint-free cloth. This ensures your glass is truly clean, with nothing left behind to interfere in the kiln.

Follow a Trusted Firing Schedule

There’s no single magic firing schedule that works for every project. The right temperature and timing depend entirely on what you’re making—its size, thickness, and whether you want a full fuse, a tack fuse, or a slump. The best approach is to learn the principles of how glass reacts to heat and start with the schedules recommended by Bullseye. Keep a detailed log for your kilns to track what works. This record will become your most valuable tool, helping you repeat your successes and learn from any surprises along the way.

Don’t Rush the Annealing Process

Annealing is the crucial process of slowly and controllably cooling your glass to relieve internal stress. If you skip or rush this step, your beautiful piece could crack days, weeks, or even months later. Just like firing schedules, annealing schedules vary based on the thickness of your project. A thicker piece needs a longer, slower cooling period to ensure it’s structurally sound. It’s a non-negotiable step for creating durable, lasting art that can be handled and enjoyed without the risk of it falling apart from hidden stress.

Protect Your Kiln Shelf (and Your Glass)

Nothing is more heartbreaking than opening your kiln to find your masterpiece permanently stuck to the shelf. To prevent this, you must use a kiln shelf separator. Products like Bullseye Shelf Primer (kiln wash), ThinFire Shelf Paper, or fiber paper create a protective barrier between the glass and the shelf. You’ll also need to apply kiln wash to any molds you use for slumping or draping. Make sure you apply a smooth, even coat and let it dry completely before firing. This simple preparation protects both your artwork and your expensive kiln furniture.

Using a Ceramic Kiln for Glass Projects

If you’re coming from the world of ceramics, you might be wondering if your trusty kiln can pull double duty for glass projects. The answer is a qualified yes—as long as it has a programmable digital controller. Glass is far less forgiving than clay and demands precise temperature control to move through the fusing and annealing cycles without building up internal stress. A manual kiln simply can’t provide the accuracy needed. You must be able to program specific ramp-up speeds, hold times, and a slow, controlled cool-down. While it’s possible to get great results, keep in mind that most ceramic kilns heat from the sides, which can be less even for glass than a kiln with top elements. You may need to experiment a bit, but a programmable controller is the non-negotiable key to success.

Choosing the Right Bullseye Compatible Products

Once you understand the science behind compatibility, picking the right supplies for your project becomes much easier. It’s all about setting yourself up for success before you even turn on the kiln. When you start with materials designed to work together, you can focus on your creativity instead of worrying about cracks. Choosing compatible products means looking beyond just the glass sheets. Your frits, powders, and stringers all play a role in the final piece. Bullseye has created a comprehensive system where everything is tested to work together seamlessly. Let’s walk through how to select the right glass, accessories, and colors for a perfect fuse.

Picking Your Perfect Sheet Glass

Here’s something every glass artist should know: not all COE 90 glass is the same. It’s a common misconception that any two glasses labeled “COE 90” will fuse together perfectly. The coefficient of expansion is a critical number, but it doesn’t tell the whole story. Bullseye conducts rigorous internal testing to ensure every sheet of their COE 90 glass is compatible with every other Bullseye product. When you stick with the Bullseye brand, you’re getting a tested and proven system, not just a matching number.

Adding Texture with Frits, Powders, and Stringers

The same rule applies to your accessory glass. To get the most reliable results, you should always pair Bullseye frits, powders, and stringers with Bullseye sheet glass. These materials are formulated to have the exact same properties as the sheet glass, ensuring a smooth and stable fuse. While it might be tempting to mix in a frit from another brand, you’re introducing a variable that can cause hidden stress in your finished piece. For consistent outcomes you can trust, keep all your glass components within the Bullseye family.

Understanding Frit Sizes and Opacity

When you’re ready to add detail and texture, Bullseye fusible glass frit is your best friend. It comes in five sizes—powder, fine, medium, coarse, and extra large—and each one creates a different effect. Fine frit is perfect for creating smooth, painterly designs, while coarse frit adds a chunky, textural feel. Powder is so fine it can be sifted to create soft gradients of color. Just like their sheet glass, all Bullseye frits are designed to work together as part of a tested system, so you can mix and match sizes with confidence.

Beyond size, you also need to consider opacity. Frits come in a huge range of colors, available in both transparent and opaque options. This choice dramatically changes how light interacts with your piece. Transparent frits will allow the colors underneath to show through, creating depth and blended hues. Opaque frits, on the other hand, will cover whatever is beneath them, providing solid blocks of color. By thoughtfully choosing your frit’s size and opacity, you can control the texture and color interactions in your work with incredible precision.

Understanding Striking vs. Non-Striking Colors

Have you ever pulled a piece from the kiln and found a color you weren’t expecting? You might have used a “striking” color. Some Bullseye glass colors look pale or colorless before they are fired. Heat activates a chemical reaction that causes the glass to “strike” and transform into its final, intended color. This isn’t a defect—it’s a unique property that creates some of the richest shades available. Always check the product description to see if a color is a striker. It’s also a great idea to fire a small test chip to see how the color develops.

Beyond Fusing: Other Kilnforming Techniques

Once you master the basics of fusing, a whole world of creative possibilities opens up. Your kiln is more than just a tool for melting glass flat; it’s a versatile instrument for shaping, texturizing, and finishing your work in countless ways. Moving beyond a full fuse allows you to create pieces with more dimension, intricate detail, and unique finishes. These techniques are the next step in developing your artistic voice in glass. Whether you want to create sculptural objects, preserve the texture of individual glass elements, or simply give a piece a final glossy polish, there’s a kilnforming technique that can help you get there.

Kilncasting

Kilncasting is a fantastic technique for creating three-dimensional glass objects, from sculptural forms to detailed relief tiles. The process involves melting glass until it flows and fills the shape of a prepared mold. You can use open-faced molds for creating pieces with a flat back and a textured front, or you can use more complex closed molds to create fully sculptural pieces. It’s a method that requires patience and precision, especially in mold-making and calculating the right volume of glass, but the results are incredibly rewarding, allowing you to produce solid, substantial art that goes beyond the flat plane of a fused panel.

Tack Fusing

If you love the look of layered glass and want to maintain the distinct shapes and textures of your design, tack fusing is the technique for you. Unlike a full fuse that melts everything smooth, a tack fuse heats the glass just enough for the individual pieces to stick together securely while retaining much of their original form and dimension. This is perfect for creating pieces with a raised, textural surface. It’s a great way to add depth and visual interest, making it a popular choice for wall art, jewelry, and decorative panels where you want the individual components to stand out.

Firepolishing

Think of firepolishing as the final touch-up for your glass art. This technique involves a quick trip back into the kiln at a relatively low temperature to give the surface of your piece a smooth, glossy finish. It’s especially useful after coldworking processes like grinding or sandblasting, which can leave the glass with a matte or frosty appearance. A quick firepolish will restore that brilliant shine without altering the overall shape of your piece. It can also be used to soften sharp edges or gently round the corners of a project, giving it a more refined and professional look.

Studio Safety and Handling

Working with glass is an incredibly rewarding process, but it’s essential to make safety your top priority. Your studio should be a space where you can create with confidence, and that starts with establishing good safety habits. From protecting yourself from sharp edges and glass dust to understanding the materials you’re working with, a little bit of precaution goes a long way. Taking the time to set up a safe workspace and handle your materials correctly not only protects your health but also ensures the integrity of your finished artwork. These practices should become second nature every time you step into your studio.

Essential Safety Gear for Your Workspace

Before you even start cutting glass, make sure your studio is equipped with the right safety gear. A well-stocked first aid kit is non-negotiable for treating the inevitable small cuts and scrapes. When working with glass powders or frits, or when grinding glass, always wear a respirator to protect your lungs from harmful dust. Good ventilation in your workspace is also crucial for keeping the air clean. Simple habits like wearing safety glasses to protect your eyes from flying shards and keeping your work area tidy can prevent most common studio accidents, letting you focus on your art.

Food Safety Considerations for Fused Glass

If you plan on making functional pieces like plates or bowls, it’s important to be aware of which glasses are food-safe. Some glass colors, particularly certain reds, oranges, and yellows, contain lead or cadmium to achieve their vibrant hues. According to Bullseye Glass, it’s best to avoid using these specific colors on the food-bearing surface of a dish. A safe and common practice is to cap these colors with a layer of clear, food-safe glass. This seals the potentially reactive layer away from contact with food, giving you the best of both worlds: brilliant color and a piece that’s safe for everyday use.

How to Store Glass Scraps Correctly

Every glass artist ends up with a colorful collection of scraps, and how you store them is incredibly important for preventing future project failures. The golden rule is to never mix glass with different COEs. Keep your leftover pieces of COE90 glass in a completely separate container from your COE96 glass scraps. Accidentally fusing a small piece of incompatible glass into a larger project can introduce stress and cause the entire piece to crack. Clearly labeling your scrap bins is a simple but critical step that will save you from a lot of potential heartbreak down the road.

Caring for Your Finished Fused Glass Art

Once you’ve pulled your beautiful creation from the kiln and it has cooled completely, the journey isn’t quite over. Proper care and handling will ensure your fused glass art remains as stunning as the day it was made. Unlike commercial glassware, handmade art glass has unique properties that require a gentler touch. Understanding how to clean and display your pieces will protect them from scratches, cracks, and the dulling effects of harsh detergents. Following a few simple guidelines will help preserve the integrity and beauty of your work for years to come, whether it’s a piece you keep for yourself or one you sell to a happy customer.

Hand-Washing and General Care

The best way to care for any piece of fused glass, whether it’s a decorative panel or a functional dish, is to wash it by hand. Use a soft cloth or sponge with warm, soapy water, and then rinse it thoroughly. This gentle approach prevents the surface from getting scratched or etched over time. For decorative pieces, a regular dusting with a soft, dry cloth is usually all that’s needed to keep them looking their best. Treating your fused glass with the same care you would any other piece of fine art is the key to its longevity.

Why to Avoid Microwaves and Dishwashers

Two of the biggest enemies of fused glass art are the microwave and the dishwasher. Putting your fused glass in the microwave is a recipe for disaster, as the uneven heating can cause thermal shock and lead to cracks. The dishwasher is equally damaging. The combination of high heat and harsh detergents can permanently etch and scratch the surface of the glass, leaving it with a cloudy, dull finish. To keep your work vibrant and intact, always advise your customers (and remind yourself!) to keep these beautiful handmade items out of these appliances.

Need More Help? Here’s Where to Go

Even the most experienced artists have questions, and knowing where to turn for reliable answers is a huge part of the creative process. Whether you’re troubleshooting a tricky firing schedule, exploring a new technique, or just need a little inspiration, there’s a wealth of information available to guide you. The glass fusing community is incredibly supportive, and thankfully, the manufacturers themselves often provide the best educational materials. You never have to feel like you’re working in a vacuum.

Tapping into these resources can help you solve problems quickly and give you the confidence to push your creative boundaries. Instead of spending hours on trial and error, you can learn from the collective experience of others and get straight to the fun part: making beautiful art. Think of it as having a whole team of mentors at your fingertips. From official technical documents to casual conversations in an online forum, the right piece of advice at the right time can make all the difference. Here are some of the best places to find help and continue growing as a glass artist.

Go Straight to the Source: Bullseye’s Resources

One of the best things about working with Bullseye glass is the company’s deep commitment to artist education. They offer a fantastic library of free online articles and video lessons that cover everything from kiln-forming basics to advanced techniques like kiln-casting and coldworking. Because their glass is so rigorously tested and designed for consistency, their guidance is always on point. If you have a specific question about their products or need a reliable firing schedule, their website is the first place you should look. It’s incredibly reassuring to know that the people who make the glass are also dedicated to helping you use it successfully.

Join Online Communities and Watch Tutorials

You don’t have to figure everything out on your own. Bullseye hosts a supportive Facebook community where you can connect with thousands of other glass artists, ask for advice, and share your latest projects. It’s a wonderful place to see what others are creating and get feedback from people who truly understand the medium. Beyond social media, Bullseye’s collection of online video lessons is an invaluable resource for visual learners. Many are free and provide clear, step-by-step instructions that make it easy to follow along, whether you’re a beginner or a seasoned pro looking to refine your skills.

Ask the Experts Your Compatibility Questions

When you’re wondering if you can mix Bullseye glass with another brand, it’s best to go straight to the source for information. Bullseye is very clear that simply matching COE numbers isn’t enough to guarantee a successful fuse. True compatibility involves more than just the coefficient of expansion; it’s about how the glasses behave throughout the entire heating and cooling cycle. They strongly recommend performing your own tests to be certain that different glasses will work well together. For a deeper understanding of the science, their TechNote on compatibility is required reading. Taking the time to test will save you from the heartbreak of a beautiful piece cracking in the kiln.

Where to Buy Authentic Bullseye Glass

Once you understand the importance of compatibility, the next step is sourcing high-quality, authentic Bullseye glass. Using genuine products is the only way to guarantee the COE 90 standard and get predictable, beautiful results in your kiln. When you invest your time and creativity into a piece, you want to be sure your materials won’t let you down. Here’s where to find what you need and how to make sure you’re getting the real deal for your next project.

Shop ArtGlassSupplies.com for Genuine Bullseye

When you’re ready to stock up on genuine Bullseye glass, we’ve got you covered. We are a reliable source for artists who need authentic materials they can trust. Our shop offers a wide selection of discounted COE90 Glass, making it easy to find the exact colors and forms you need without breaking your budget. Whether you’re looking for full sheets, frits, or stringers, you can shop with confidence knowing you’re getting quality materials that will perform beautifully in your studio. We make it simple to get everything you need in one place.

Is It Real Bullseye? How to Tell

To ensure you’re working with genuine Bullseye products, always purchase from a reputable and authorized dealer. Authentic Bullseye glass is known for its consistent quality, and it often comes with specific labeling on the sheets. Be cautious when buying from third-party marketplaces or sellers offering deals that seem too good to be true, as you can’t verify the glass’s origin or storage conditions. Sticking with a trusted supplier like ArtGlassSupplies.com means you never have to worry about authenticity. You can focus on your art, confident that your stained glass and fusible materials are exactly what they claim to be.

Save with Volume Discounts and Special Offers

If you’re stocking a teaching studio, working on a large commission, or just love having a full palette of colors on hand, buying in bulk is a smart way to save. We offer competitive, wholesale-level pricing that makes it more affordable to get the quantities you need. This is especially helpful for schools and art institutions that need to make their budgets stretch further. We are committed to getting your supplies to you safely and are always looking for ways to provide more value to our community of artists. Be sure to check our site for special sales and promotions on everything from glass to kilns.

Related Articles

• COE 90 vs 96: Which Glass Should You Choose?
• The Ultimate Guide to COE 90 Glass Suppliers
• The Complete Guide to COE 90 Fusing Glass Supplies
• COE Glass Meaning: A Beginner’s Guide to Fusing

Frequently Asked Questions

What does COE 90 actually mean? Does it guarantee any two COE 90 glasses will work together? Think of the COE number as a starting point, not a final guarantee. It measures how much glass expands and contracts with heat, which is incredibly important. However, true compatibility also involves other factors, like the glass’s chemical makeup. Bullseye has engineered its entire line of products to work together as a complete system. That’s why another brand’s COE 90 glass might not be a perfect match and could cause stress in your final piece.

I have some scrap glass from another brand that’s also COE 90. Is it really that bad to mix it with my Bullseye glass? It’s a gamble that most experienced artists avoid. While it might seem fine, different manufacturers use unique formulas that can create invisible stress when fused together. This stress can cause your project to crack days, weeks, or even months after it comes out of the kiln. If you absolutely must mix brands, the only way to be safe is to run a compatibility test on small strips first.

What’s the difference between fusing and slumping? Can I do them at the same time? Fusing and slumping are two separate steps that require different firing schedules. Fusing happens at a higher temperature to melt individual pieces of glass into one solid, flat slab. Slumping happens at a lower temperature, which just softens that slab enough to gently bend or “drape” into a mold. For the best results, you should always fuse your project flat first, let it cool completely, and then run a separate slumping cycle.

Do I really need to clean my glass before I put it in the kiln? Yes, absolutely! This is one of the most important steps for a professional finish. Even if the glass looks clean, invisible oils from your fingerprints, dust, or marker residue can cause cloudy spots or a scummy surface texture called devitrification during firing. Taking a few moments to clean every piece with a good glass cleaner ensures your final project is as clear and vibrant as you intended.

What are “striking” colors, and how do I know if I’m using one? Striking colors are a bit like magic. They often look pale or even clear before firing, but a chemical reaction in the kiln transforms them into their final, rich color. This isn’t a flaw; it’s a special property that creates some of the most beautiful shades available. The product description will always tell you if a glass is a striker. It’s a great idea to fire a small test piece so you know exactly what to expect.