{"id":1722,"date":"2026-07-08T10:00:00","date_gmt":"2026-07-08T10:00:00","guid":{"rendered":"https:\/\/www.artglasssupplies.com\/blog\/glass-slumping-temperature-guide\/"},"modified":"2026-07-08T10:00:00","modified_gmt":"2026-07-08T10:00:00","slug":"glass-slumping-temperature-guide","status":"publish","type":"post","link":"https:\/\/www.artglasssupplies.com\/blog\/glass-slumping-temperature-guide\/","title":{"rendered":"Mastering Glass Slumping Temperature: A Firing Guide"},"content":{"rendered":"

Opening the kiln shouldn’t feel like a game of chance. You can move from hoping for the best to knowing what to expect. That confidence comes from taking control of your firing process, and the most important variable you can control is temperature. Mastering the correct glass slumping temperature for your specific setup turns an unpredictable art form into a reliable craft. It\u2019s the difference between a happy accident and intentional design. This guide will give you the foundational knowledge to build repeatable firing schedules, empowering you to create the exact forms you envision, project after project, with confidence.<\/p>\n

CTA Button<\/title><\/p>\n<style>.cta-container{display:flex;justify-content:center;margin:40px 0}.cta-button{display:inline-flex;align-items:center;justify-content:center;padding:12px 28px;font-size:16px;font-weight:700;color:#000!important;background-color:#fff!important;border:none!important;border-radius:50px!important;cursor:pointer!important;text-decoration:none!important;transition:all .3s ease-in-out!important;box-shadow:0 0 4px rgba(0,0,0,.15)!important}.cta-button i{margin-right:8px;transition:color .3s ease-in-out!important}.cta-button:hover{color:#2a65c9!important}.cta-button:hover i{color:#2a65c9!important}<\/style>\n<div class=\"cta-container\"><a href=\"https:\/\/www.artglasssupplies.com\/ticket-create\" class=\"cta-button\"><i>\u2191<\/i> Contact Us<\/a><\/div>\n<\/div>\n<h2>Key Takeaways<\/h2>\n<ul>\n<li><strong><a href=\"https:\/\/www.artglasssupplies.com\/blog\/what-you-need-to-know-about-kilns-for-glass-fusing\/\">Master the three phases of firing<\/a><\/strong>: A successful slump depends on a controlled schedule: ramp up the heat slowly to prevent cracks, hold at the target temperature to shape the glass, and cool down patiently through the annealing phase to create a strong, durable piece.<\/li>\n<li><strong>Fine-tune your temperature for each project<\/strong>: The perfect slumping temperature is not one-size-fits-all; you must adjust it based on the glass COE (like COE90 or COE96), the thickness of your piece, and the specific shape and depth of your mold.<\/li>\n<li><strong>Prep your mold and run a test fire<\/strong>: Avoid common frustrations with two simple habits. Always coat your mold with kiln wash to prevent sticking, and run a small test with new molds or glass to confirm your firing schedule before committing to your final project.<\/li>\n<\/ul>\n<h2>Glass Slumping vs. Fusing: What’s the Difference?<\/h2>\n<p>If you\u2019re getting into kiln-formed glass, you\u2019ve probably heard the terms \u201cslumping\u201d and \u201cfusing\u201d used together. While both techniques use a kiln to transform glass, they have very different goals. Think of it this way: fusing is about joining, while slumping is about shaping. Fusing melts separate pieces of glass into a single, solid piece. Slumping takes that solid piece and drapes it over or into a mold to give it a three-dimensional form.<\/p>\n<p>Slumping uses lower temperatures, typically between 1200\u00b0F and 1300\u00b0F. At this heat, the glass becomes soft and pliable, like taffy. Gravity then does the work, causing the glass to gently “slump” and take the shape of the <a href=\"https:\/\/www.artglasssupplies.com\/molds\">mold<\/a> it’s resting on. This process is perfect for creating functional pieces like bowls, plates, and platters, or adding gentle curves to a decorative panel. You\u2019re not melting the glass completely, just making it flexible enough to bend.<\/p>\n<p>Fusing, on the other hand, requires much higher temperatures, usually from 1300\u00b0F to 1500\u00b0F. The goal here is to fully melt two or more pieces of compatible glass, like <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a>, so they flow together and become one. This is how artists create intricate patterns, colorful tiles, and unique components for jewelry. For example, many artists working with <a href=\"https:\/\/www.artglasssupplies.com\/coe96\">COE96 glass<\/a> find that a full fuse happens right around 1450\u00b0F.<\/p>\n<p>Because of these differences, the standard practice is to fuse your project first, then slump it in a separate firing. This two-step process gives you the most control. You can focus on creating your perfect flat design during the fusing stage. Once it has cooled and you\u2019re happy with it, you can move on to the slumping stage to give it shape. Trying to fuse and slump at the same time often leads to trapped air bubbles and a loss of detail in your design. Your <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a> is the key to both processes, but understanding when and why to use each technique will make all the difference in your final piece.<\/p>\n<h2>Finding the Right Slumping Temperature<\/h2>\n<p>Think of finding the right slumping temperature as discovering your kiln\u2019s unique personality. While there are established guidelines, every kiln fires a little differently. The key is to start with a solid baseline and adjust based on your specific glass, mold, and desired outcome. Getting that perfect, gentle drape requires a bit of patience and observation, but once you dial it in, you\u2019ll be able to create consistent, beautiful pieces every time. Let\u2019s walk through the most important factors to get you started on the right foot.<\/p>\n<h3>Slumping Temperatures for COE90 vs. COE96 Glass<\/h3>\n<p>Your glass\u2019s Coefficient of Expansion (COE) is the first thing to consider. For artists working with <a href=\"https:\/\/www.artglasssupplies.com\/coe96\">COE96 glass<\/a>, the sweet spot for slumping is generally between 1180\u00b0F and 1250\u00b0F. If you push the temperature too high, you risk your piece over-slumping and losing its defined shape. For context, most COE96 glass reaches a full fuse around 1450\u00b0F, so slumping happens at a much lower temperature.<\/p>\n<p>If you\u2019re using <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a>, you\u2019ll find it typically needs a slightly higher temperature to achieve a similar slump. Because every kiln has its own quirks, it\u2019s always a great idea to run a small test fire to see how your specific glass and kiln combination behaves.<\/p>\n<h3>How Your Mold’s Shape Affects Temperature<\/h3>\n<p>The shape and complexity of your mold play a huge role in your firing schedule. The final form of your glass is determined by both the peak temperature and how long you hold it there. If the temperature gets too high, the glass becomes more fluid and can slump too quickly, causing it to lose crisp details or pull away from the edges of intricate <a href=\"https:\/\/www.artglasssupplies.com\/molds\">molds<\/a>. A deep, dramatic mold will require a different approach than a shallow, simple one. Think of it as a conversation between the glass and the mold; you\u2019re just guiding it with heat.<\/p>\n<h3>How to Tell If Your Temperature Is Off<\/h3>\n<p>Keeping a close eye on your project is the best way to learn what\u2019s happening inside your kiln. A great habit is to start checking your glass every five to ten minutes once the temperature climbs past 1040\u00b0F. This is when the glass begins to soften and move. If you notice your piece isn\u2019t slumping as you expected, your temperature is probably too low. As a rule of thumb, glass really starts to move around 1225\u00b0F. By carefully observing the process, you\u2019ll learn the visual cues that tell you when your glass has slumped perfectly, helping you fine-tune your firing schedules for future projects.<\/p>\n<h2>What Factors Influence Slumping Temperatures?<\/h2>\n<p>Finding the perfect slumping temperature isn’t about a single magic number. It\u2019s more like a recipe where you adjust the ingredients based on what you\u2019re making. The ideal temperature and firing schedule for your project depend on a few key variables. Getting familiar with these factors will help you achieve consistent, beautiful results every time you fire up your kiln. Let’s look at the three most important elements: the type of glass you’re using, its thickness, and the shape of your mold.<\/p>\n<h3>Glass Type and COE<\/h3>\n<p>The type of glass you use is the biggest factor in determining your slumping temperature. Every glass has a unique personality, and its Coefficient of Expansion (COE) tells you how much it will expand and contract when heated. Because of this, <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a> and COE96 glass have different working ranges. While most slumping happens between 1180\u00b0F and 1250\u00b0F, you’ll need to fine-tune your schedule based on the specific glass you’re working with. It’s also why you should never mix glass with different COEs in one project; they’ll cool at different rates, creating stress that can cause your piece to crack. Always stick to one COE for a successful slump.<\/p>\n<h3>Glass Thickness<\/h3>\n<p>The thickness of your glass piece directly impacts your firing schedule, especially the heating and cooling rates. Think of it like cooking: a thin steak cooks much faster than a thick roast. Similarly, thicker glass needs to be heated and cooled more slowly to prevent thermal shock, which is when the glass cracks due to rapid temperature changes. While your target slumping temperature might stay the same, you’ll need to program your <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a> with a slower ramp rate. A thicker piece may also require a longer hold at the peak temperature to ensure the heat penetrates evenly and the glass slumps uniformly into the mold.<\/p>\n<h3>Mold Shape and Depth<\/h3>\n<p>The mold you choose plays a huge role in your firing schedule. A simple, shallow mold requires less work from the glass than a deep, intricate one. For a piece to slump into a deep mold with sharp details, it needs to become soft enough to stretch and conform to every curve. This might mean using a slightly higher temperature or holding it at the peak temperature for longer. However, there’s a delicate balance. Firing too hot can make the glass overly fluid, causing it to pull away from the edges or lose crisp details. Each <a href=\"https:\/\/www.artglasssupplies.com\/molds\">mold<\/a> has its own sweet spot, so it\u2019s always a good idea to run a test fire with a new one.<\/p>\n<h2>What Does a Slumping Firing Schedule Look Like?<\/h2>\n<p>Think of a firing schedule as a recipe for your glass project. It\u2019s a set of instructions that tells your kiln exactly how hot to get, how fast to get there, and how long to stay at certain temperatures. While every project is a little different, most slumping schedules follow the same three-part structure: a slow ramp up to temperature, a hold to shape the glass, and a careful cooling and annealing phase.<\/p>\n<p>Following a schedule is the key to getting consistent, beautiful results and avoiding frustrating cracks or an under-slumped piece. It takes the guesswork out of the process and puts you in control. Let\u2019s walk through what each phase looks like so you can fire your next project with confidence.<\/p>\n<h3>Phase 1: Ramping Up the Heat<\/h3>\n<p>The first phase is all about gradually increasing the temperature inside your <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a>. This is called the “ramp.” You can’t just turn the heat all the way up; doing so would cause thermal shock and crack your glass before it even has a chance to slump. A slow and steady ramp is essential. Most slumping happens between 1180 and 1250 degrees Fahrenheit. As the experts at Wissmach Glass note, “Typically slumping temperatures range from 1180 -1250 degrees. Be aware it is possible to over-slump your glass using too hot a temperature.” The goal is to bring the glass and the mold up to temperature together, gently and evenly, setting the stage for a perfect slump.<\/p>\n<h3>Phase 2: The Slumping Hold<\/h3>\n<p>Once your kiln reaches the target temperature, it\u2019s time for the “hold” or “soak.” During this phase, the kiln maintains a steady temperature, allowing the heat to soften the glass enough for gravity to pull it down into the mold. The length of this hold is critical. A simple, shallow piece might only need a short hold. For instance, you might “Hold at 1200\u00b0F for 10 minutes for a simple shape like a sushi plate.” However, a project with a deeper or more intricate <a href=\"https:\/\/www.artglasssupplies.com\/molds\">mold<\/a> will likely need a longer hold time to give the glass enough time to conform to every detail. This is the phase where your piece truly takes its shape.<\/p>\n<h3>Phase 3: Cooling and Annealing<\/h3>\n<p>After your glass has slumped perfectly, you can\u2019t just turn the kiln off. The final phase, cooling and annealing, is arguably the most important step for creating a strong, durable piece. Annealing is the process of cooling the glass very slowly to relieve internal stresses that build up during heating and shaping. A good rule of thumb is to “slowly decrease the temperature (e.g., 100\u00b0 per hour) to release stress in the glass.” Rushing this step can cause your project to crack days or even weeks later. As glass pros will tell you, “The anneal soak and cool steps are very important to make sure the glass cools evenly and doesn’t crack later.” Patience here ensures your beautiful <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a> creation lasts a lifetime.<\/p>\n<h2>How Fast Should You Heat and Cool Your Glass?<\/h2>\n<p>Patience is a virtue, especially in glass art. The speed at which you heat and cool your glass is just as important as the peak temperature you hit. Rushing the process can lead to thermal shock, which is a fancy way of saying your beautiful project might crack from stress. A carefully planned firing schedule, with controlled heating and cooling rates, is your best defense against disaster. Let’s walk through how to manage your kiln’s timing to ensure your glass slumps perfectly and comes out strong and stable.<\/p>\n<h3>Set Your Ramp Rate to Avoid Thermal Shock<\/h3>\n<p>Think of your glass like a person easing into a hot bath. If you jump in too fast, it’s a shock to the system. The same goes for your glass project. To avoid thermal shock and prevent cracks, you need to increase the temperature in your <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a> slowly. This gradual heating is called the “ramp rate.” A good rule of thumb is to ramp up at a rate of 300\u00b0F to 400\u00b0F per hour. This gentle approach allows the entire piece of glass to heat evenly, minimizing internal stress and setting you up for a successful slump without any heartbreaking cracks.<\/p>\n<h3>Annealing Times Based on Glass Thickness<\/h3>\n<p>Once your glass has slumped and you’ve started the cooling process, the most critical phase is annealing. This is where the glass rests at a specific temperature (usually around 900\u00b0F) to relieve internal stress. The time it needs to spend in this phase depends entirely on its thickness. A standard 1\/4-inch thick piece of <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a> might need an annealing hold of about an hour. However, if you’re working with a much thicker piece, or one with significant variations in thickness, you’ll need to extend that hold time considerably. Rushing this step is a common cause of “delayed” cracking that shows up hours or even days later.<\/p>\n<h3>How to Cool Your Glass Safely<\/h3>\n<p>After the annealing hold is complete, you can’t just turn off the kiln. The rest of the cooling journey must also be controlled. From the annealing temperature, you should cool the glass slowly to prevent new stress from forming. A safe rate is about 100\u00b0F per hour, especially until you get below 700\u00b0F. For projects that are very thick, large, or have dramatic shapes created with deep <a href=\"https:\/\/www.artglasssupplies.com\/molds\">molds<\/a>, you may need to slow this rate even further. Once the kiln is below 100\u00b0F, you can crack the lid to peek, but it’s always safest to wait until it’s completely at room temperature before opening it all the way and removing your art.<\/p>\n<h2>Why Is Annealing So Important in Glass Slumping?<\/h2>\n<p>After all the work of designing, cutting, and firing your glass, the last thing you want is for it to crack. This is where annealing comes in. Think of it as a crucial cool-down phase that makes your finished piece strong and durable. When glass is heated to slumping temperatures, its molecules are moving around and are under a lot of stress. Annealing is the process of holding the glass at a specific temperature and then cooling it very slowly. This controlled process allows the entire piece to cool evenly, relieving that internal stress.<\/p>\n<p>Skipping or rushing this step is a gamble. Without proper annealing, your beautiful slumped bowl or plate could develop a crack hours, days, or even weeks after it comes out of the <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a>. It\u2019s a non-negotiable part of the process that ensures your art will last. Every piece, whether it’s made from <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90<\/a> or COE96 glass, needs to be annealed to become a stable, finished work of art. It\u2019s the final, quiet step that makes all the difference.<\/p>\n<h3>The Right Way to Anneal Your Glass<\/h3>\n<p>Proper annealing involves two key stages: the soak and the slow cool-down. Once your glass has slumped into its final shape, your firing schedule will bring the temperature down to the annealing point, which is typically around 900\u00b0F to 960\u00b0F. The <a href=\"https:\/\/www.artglasssupplies.com\/blog\/a-complete-guide-to-glass-slumping\/\">kiln<\/a> then “soaks” or holds at this temperature, usually for about an hour for a standard \u00bc-inch thick piece. This hold ensures the entire piece of glass, from the core to the surface, reaches a uniform temperature. After the soak, you begin the slow cooling process, reducing the temperature gradually to release the stress in the glass before it cools completely.<\/p>\n<h3>The Risks of Rushing or Skipping Annealing<\/h3>\n<p>I know how tempting it is to peek inside the kiln or try to speed things up, but patience during the cooling phase is your best friend. The biggest risk of improper annealing is thermal shock. If glass cools too quickly, the outside contracts faster than the inside, creating immense tension that results in cracks. A piece might look perfect when you pull it from the kiln, only to break later from the hidden stress. Even opening the kiln door too early can introduce a rush of cool air and cause your project to crack instantly. Following a proper annealing schedule is the best insurance you can give your artwork.<\/p>\n<h2>Common Slumping Mistakes (And How to Avoid Them)<\/h2>\n<p>Even the most experienced artists run into trouble now and then. Glass can be unpredictable, but many common slumping issues come down to a few key missteps. The good news is that they are all avoidable with a little patience and preparation. Let’s walk through some of the most frequent mistakes I see and, more importantly, how you can sidestep them to get a beautiful slump every time.<\/p>\n<h3>Heating Too Fast<\/h3>\n<p>I know how tempting it is to rush the heating process, but this is one of the quickest ways to ruin a project. Heating your glass too quickly, especially below 1000\u00b0F, can cause it to crack from thermal shock. Think of it as a jolt to the system that the glass just can’t handle. The bigger and thicker the piece, the more susceptible it is to cracking. The solution is simple: slow down. A gradual ramp rate gives the glass time to adjust to the rising temperature, ensuring it heats evenly from the edges to the center. A programmable <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kiln<\/a> is your best friend here, as it lets you set a slow, steady pace for this critical initial phase.<\/p>\n<h3>Over-firing or Under-firing<\/h3>\n<p>Finding that “just right” temperature can feel like a moving target. If you under-fire your piece, it won’t fully drop into the mold, leaving you with a shape that\u2019s not quite what you envisioned. On the other hand, it\u2019s very possible to over-slump your glass by using too hot a temperature. Firing at too high a temperature makes the glass overly fluid, causing it to slump too far and lose its crisp edges. Your beautiful details can become soft and undefined. To avoid this, get familiar with your materials. Different types of glass, like <a href=\"https:\/\/www.artglasssupplies.com\/coe90\">COE90 glass<\/a>, have different ideal slumping ranges. Always check the manufacturer’s recommendations and keep detailed notes on what works in your specific kiln.<\/p>\n<h3>Forgetting to Prep Your Mold<\/h3>\n<p>This is a mistake you\u2019ll only make once. If you forget to apply kiln wash or a primer to your mold, the glass will fuse directly to it during firing. This will likely destroy both your project and your mold. A well-prepared mold can last for many uses, ensuring better results and protecting your investment. Before every firing, make sure your mold is coated with a thin, even layer of kiln wash and that it’s completely dry before you place your glass on it. Taking a few extra minutes for this step is non-negotiable for a successful outcome. It\u2019s a simple habit that will save you a lot of frustration and money on new <a href=\"https:\/\/www.artglasssupplies.com\/molds\">molds<\/a>.<\/p>\n<h3>Skipping a Test Fire<\/h3>\n<p>When you’re working with a new mold, a different type of glass, or even a new kiln, a test fire is your secret weapon. It might feel like an extra step, but it can save you from ruining a large or intricate project. Use a small scrap piece of the same glass you plan to use for your final piece and run it through your intended firing schedule. This allows you to see exactly how the glass will move and at what temperature it achieves the perfect slump. You can even peek into the kiln every 10 minutes or so during the slumping phase to observe the process. This small investment of time and material provides invaluable information and builds your confidence for the main event.<\/p>\n<h2>Essential Tools for Temperature Control<\/h2>\n<p>Achieving that perfect, graceful slump isn’t just about knowing the right temperatures; it’s about having the right equipment to execute your plan. Think of it as setting up your kitchen before you start cooking a complex meal. The right tools give you the control and precision you need to get predictable, beautiful results every time you fire up the kiln. Without them, you\u2019re leaving far too much to chance. Let\u2019s walk through the essential hardware you\u2019ll need to master the slumping process and create the stunning glass art you envision. These are the non-negotiable items that will form the foundation of your slumping studio, so it pays to choose them wisely from the very beginning.<\/p>\n<h3>Find the Right Kiln for Slumping<\/h3>\n<p>Your kiln is the heart of your slumping setup, and you need one that\u2019s up for the job. While you don\u2019t need a massive kiln, especially for smaller projects, it must meet a few key requirements. Look for a glass kiln that can comfortably reach temperatures around 1400\u00b0F. More importantly, you want one that heats your glass evenly from the top and sides. This even heating is your best defense against the thermal shock that can cause cracks and breaks. Many modern <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kilns<\/a> come with digital controllers, which are fantastic for programming your exact firing schedule. This feature gives you incredible control over the entire process, from the initial ramp-up to the final cooling phase.<\/p>\n<h3>Pick the Perfect Slumping Mold<\/h3>\n<p>If the kiln is the heart, the mold is the soul of your project. It dictates the final shape and texture of your piece, transforming a flat sheet of glass into a functional bowl, a decorative plate, or a sculptural form. When you\u2019re browsing for <a href=\"https:\/\/www.artglasssupplies.com\/molds\">slumping molds<\/a>, you’ll find they are usually made from durable materials like ceramic or stainless steel. These materials are built to handle the intense heat of the kiln without warping or breaking down, ensuring you get a clean, consistent shape every time you fire. Remember to always prepare your mold with a quality kiln wash or shelf paper to prevent the glass from sticking.<\/p>\n<h3>Tools to Monitor Your Kiln’s Temperature<\/h3>\n<p>Guesswork has no place in glass slumping. To get beautiful, consistent results, you need to precisely follow a firing schedule. This means carefully controlling your ramp rates, soak times, and cooling. While many modern <a href=\"https:\/\/www.artglasssupplies.com\/kilns\">kilns<\/a> have built-in digital controllers and pyrometers (which are essentially high-temperature thermometers), it’s still wise to understand how they work. These tools allow you to program and monitor every stage of the firing. For example, a low-temperature slumping schedule might have a top temperature around 1100\u00b0F. A reliable controller ensures your kiln hits that mark exactly and holds it for the right amount of time, giving you the power to slump your glass perfectly.<\/p>\n<h2>Related Articles<\/h2>\n<ul>\n<li><a href=\"https:\/\/www.artglasssupplies.com\/blog\/how-to-prepare-for-glass-fusing-a-complete-fusing-guide\/\">A Complete Guide on, How to Prepare for Glass Fusing?<\/a><\/li>\n<li><a href=\"https:\/\/www.artglasssupplies.com\/blog\/what-you-need-to-know-about-kilns-for-glass-fusing\/\">The Ultimate Glass Fusing Kiln Guide for Artists – ArtGlassSupplies<\/a><\/li>\n<li><a href=\"https:\/\/www.artglasssupplies.com\/blog\/a-complete-guide-to-glass-slumping\/\">Glass Slumping 101: A Complete Beginner\u2019s Guide – ArtGlassSupplies<\/a><\/li>\n<\/ul>\n<div data-mega-embed=\"true\"><meta charset=\"utf8\"><title>CTA Button<\/title><\/p>\n<style>.cta-container{display:flex;justify-content:center;margin:40px 0}.cta-button{display:inline-flex;align-items:center;justify-content:center;padding:12px 28px;font-size:16px;font-weight:700;color:#000!important;background-color:#fff!important;border:none!important;border-radius:50px!important;cursor:pointer!important;text-decoration:none!important;transition:all .3s ease-in-out!important;box-shadow:0 0 4px rgba(0,0,0,.15)!important}.cta-button i{margin-right:8px;transition:color .3s ease-in-out!important}.cta-button:hover{color:#2a65c9!important}.cta-button:hover i{color:#2a65c9!important}<\/style>\n<div class=\"cta-container\"><a href=\"https:\/\/www.artglasssupplies.com\/ticket-create\" class=\"cta-button\"><i>\u2191<\/i> Contact Us<\/a><\/div>\n<\/div>\n<h2>Frequently Asked Questions<\/h2>\n<p><strong>Can I fuse and slump my project in one firing to save time?<\/strong> I know it\u2019s tempting to combine steps, but this is one shortcut you\u2019ll want to avoid. Fusing and slumping happen at very different temperatures and have opposite goals. Fusing requires high heat to melt glass pieces together, which would cause your project to become a liquid puddle in a slumping mold. Slumping uses lower temperatures to gently soften the glass. For the best results and the most control, always fuse your flat design first. Once it has cooled, you can place it on a mold for a separate slumping fire.<\/p>\n<p><strong>My slumped piece looked fine, but it cracked a day later. What went wrong?<\/strong> This is a classic and heartbreaking sign of an improper annealing schedule. When glass heats and cools, it builds up internal stress. The annealing phase, which involves holding the glass at a specific temperature and then cooling it very slowly, is designed to relieve that stress. If this step is rushed or skipped, the stress remains trapped in the glass. Your piece might look perfect, but it’s a ticking time bomb that can crack from a small temperature change or vibration days or even weeks later.<\/p>\n<p><strong>Why is it so important to only use one type of glass, like all COE90, in a project?<\/strong> Think of the COE, or Coefficient of Expansion, as the glass’s personal fingerprint for how much it grows and shrinks with heat. Different COEs mean different rates of expansion. If you mix glass with different COEs, they will fight against each other as they cool, creating stress that will inevitably crack your piece. To ensure a strong, stable final product, you must stick to using glass with the same COE throughout your entire project.<\/p>\n<p><strong>How do I know when my glass is perfectly slumped without opening the kiln too early?<\/strong> This is where you get to play detective. It\u2019s not about guessing, but about careful observation. Once your kiln\u2019s temperature climbs past 1100\u00b0F, you can start peeking (quickly!) every 10 to 15 minutes. You\u2019re looking for the moment when the glass has fully relaxed into the shape of the mold. A perfect slump means the glass has draped evenly and all the edges have dropped. Keeping a detailed log of your firings will also help you learn exactly how your kiln behaves.<\/p>\n<p><strong>Do I really need to re-apply kiln wash to my mold before every single firing?<\/strong> Yes, absolutely. Kiln wash is the crucial barrier that prevents your glass from sticking to your mold. Even if it looks like there\u2019s still a coating from the last firing, it\u2019s likely compromised with tiny cracks or thin spots. A fresh, even coat of kiln wash is the best and cheapest insurance you can have to protect both your beautiful glass project and your valuable mold from being ruined.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Get clear tips on finding the ideal glass slumping temperature, plus firing schedules and troubleshooting advice for beautiful kiln-formed glass projects.<\/p>\n","protected":false},"author":5,"featured_media":1721,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-1722","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-glass-fusing"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/posts\/1722","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/comments?post=1722"}],"version-history":[{"count":0,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/posts\/1722\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/media\/1721"}],"wp:attachment":[{"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/media?parent=1722"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/categories?post=1722"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.artglasssupplies.com\/blog\/wp-json\/wp\/v2\/tags?post=1722"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}