There’s something deeply satisfying about the idea that you can melt glass in a kiln. Subject some hard, smooth glass pieces to high temperatures, and then watch as they dissolve into a whole new form.

Just imagine all the colorful, creative possibilities! But how exactly do you go about melting glass in a kiln and transforming it into a new creation?

Follow these beginner steps to get started.

The Basics of Glass Melting

Glass is a clear, hard material typically made from silica sand (silicon dioxide), soda ash (sodium carbonate), and lime (calcium oxide). It has the unique molecular structure of something called an “amorphous solid.”

As a result, glass doesn’t transition from a solid to liquid phase in an instant (like water). Instead, glass melts slowly when heated.

So melting glass at home takes some patience and control. As does cooling it, which is essential to creating a durable glass object.

If you cool glass too quickly, it stiffens unevenly and can cause thermal shock, trapping stress points into the glass. You need to cool your creation slowly, through a process called glass annealing.

Your kiln is the key to success in both melting and annealing, so choose a high-quality kiln (more on that below).

Glass Fusing at a Glance

What can you do as a result of melting glass? The best thing is to fuse the molten glass into a different design and shape.

This is the art of glass fusion. Fused glass makes wonderful jewelry, picture frames, wall art, and more. The temperature you top out at will determine how completely fused the glass becomes:

• Tack fuse – 1,350 - 1,370 °F – Glass pieces stick together but maintain edges and form.
• Medium/soft fuse – 1,400 - 1,450 °F – Edges soften and round off.
• Full fuse – 1,450 - 1,470 °F – Creating a smooth, fully fused surface.

What You’ll Need

You need only a few fundamental tools and materials to melt glass in a kiln.

1. A quality kiln and kiln accessories
2. Personal protective equipment
3. Glass pieces for melting
4. Glass cutting tools

What Makes a Good Kiln for Melting Glass?

Obviously, your kiln must be able to heat up high enough to melt glass pieces—at least to the fusing temperatures cited above.

But there’s a lot more to it than heating capacity. You want a kiln that’s safe and easy to use.

For example, Hot Shot glass kilns have Cool-Touch technology that prevents burns. Our kilns also come with precise temperature control and two controller options for simple operation—even for beginners. You can choose from a range of sizes that are in stock and ready to ship.

Along with your kiln, you may need accessories including:

• Kiln shelves to simplify cleanup
• Kiln paper to protect the shelf surface
• Kiln wash to prevent melted glass from sticking to surfaces
• Molds – especially for glass working techniques such as slumping and casting

Selecting Glass for Melting

To give yourself the best chances of success in melting and fusing, you might want to start by using pieces of glass designed specifically for this kind of glass working.

Look for a type of glass labeled “fusible” from trusted brands such as Bullseye, Spectrum, Uroboros, and Wissmach. Each offers lots of options for glass in sheets, stringers (spaghetti-like strands), confetti, and millefiori (small beads with colorful patterns).

Whatever supplier you choose, the most important bit of info to keep in mind is coefficient of expansion (COE).

COE is a measure of how much glass will expand when heated and contract when cooled. You want glass with the same COE to help prevent cracking and shattering of your melted and fused creations.

For more information on COE and other kiln-forming concepts, check out our guide to kiln-formed glass.

Glass Melting and Fusing, Step by Step

Step 1: Preparing Your Glass

First, gather the glass pieces you’d like to melt.

Depending on the design you envision, you may want to cut your pieces into different shapes and sizes. Make sure they’re free of dust and debris that could lead to imperfections in your final product. Then arrange your glass pieces however you’d like them to fuse together.

Step 2: Preparing Your Kiln

Install a kiln shelf covered with kiln paper.

Coat your molds (if you’re using any) with a kiln wash.

Step 3: Programming Your Kiln

Now it’s time to get to the good stuff: programming the entire process of melting and fusing glass in a kiln—then watching this amazing transformation happen!

What follows is a general guideline for programming a kiln to melt the glass pieces of a small project (up to 8 inches in diameter) and create a full fuse.

The recommended temps are based on glass with a COE of 96, which is most common. For glass with COE of 90 (another common spec), add 20 °F to the top temperature.

Keep in mind that different kilns and different controllers will involve somewhat different processes. But the fundamentals are the same regardless of who made your equipment. Still, it bears repeating that the firing schedules and directions for your project will vary based on the glass, the design, the technique, and your kiln.

These directions refer to a Hot Shot kiln with a standard controller interface, the Novus N20K48 PID (proportional–integral–derivative).

More about our controller options

Setup

First, turn on the kiln via the black button on the bottom right. Toggle on the controller via the switch on the left.

On the home screen, two numbers appear. The top number is the current temperature inside the oven; the bottom is the current set point temperature.

To begin programming, hold down the P button until PROG shows at the bottom of the screen. Then release the P button.

Access the first of a series of program parameters by pressing and releasing the P button. Use the up and down arrow keys to adjust the following settings as desired, then press P to move to the next parameter.

• Pr.tY – Priority. Do you want this program to take priority over other saved programs?
• Pr.tb – Units. Which units are you using for the program (default is minutes).
• Pr R – Repeat. Do you want the program to automatically repeat?
• Pr N – Number. Assign a number to the program. The system can save up to 20 different programs.
• Ptol – Tolerance. How close to your set points do you want the program to be?

Press P again. Now it’s time to program the steps.

Ramping Up

Program the kiln to gradually raise the temperature. Set the parameters of each step by using the arrow keys, and then press P to move to the next parameter. If you need to back up, press the F key (on the right).

For this full fuse program, ramp up the temperature in two stages:

1. at 400 °F per hour to 1,000 °F, holding at that point for 15 minutes; then
2. at 900 °F per hour up to 1,460 °F, holding for 30 minutes there.

Program Ramp Up 1

 First, calculate the time required for this stage based on the ramp rate.

Then enter the program:

1. PSP 0 – Program setpoint zero – Start at ambient temperature: 70 °F
2. Pt 1 – Program time – 1:39
3. Pt E – Event – If you want to add an alarm to let you know when this program is complete, you can do so at this screen. Otherwise, press P to continue.
4. PSP 1 – 1,000 °F
5. Pt 2 – 0:15 minutes
6. PSP 2 – 1,000 °F, to hold at the same temperature

Program Ramp Up 2

Calculate the time required for this stage.

Then continue entering the program:

1. Pt 3 – 0:30 minutes
2. PSP 3 – 1,460 °F

Soak/Hold

Enter the soak time at this top temperature:

1. Pt 4 – 0:20 minutes
2. PSP 4 – 1,460 °F

Cooldown & Anneal

At this point, you should have a full fuse of your melted glass!

Now it’s time to cool things down in several stages:

1. At 1,000 °F per hour to 960 °F, holding at that point for 60 minutes; then
2. At 200 °F per hour down to 800 °F, holding for 10 minutes; and finally
3. At 400 °F per hour down to 300 °F.

Cooldown Ramp 1

Calculate the time required for this stage.

Then continue entering the program:

1. Pt 5 – 0:30 minutes
2. PSP 5 – 960 °F

Soak/Hold

Enter the soak time at this top temperature:

1. Pt 6 – 1:00 hour
2. PSP 6 – 960 °F

Cooldown Ramp 2

Calculate the time required for this stage.

Then continue entering the program:

1. Pt 7 – 0:48 minutes
2. PSP 7 – 800 °F

Soak/Hold

Enter the soak time at this top temperature:

1. Pt 8 – :10 minutes
2. PSP 8 – 800 °F

Cooldown Ramp 3

Calculate the time required for this stage.

 Then continue entering the program:

1. Pt 9 – 0:75 minutes
2. Pt E – You may want to set an alarm to let you know the program is complete, so press the up arrow at this parameter to select Yes. Then press P to continue.
3. PSP 9 – 300 °F

Step 4: Wrapping Up

After pressing P to lock in the final parameter, the LP (loop program) option appears on the screen.

This feature is useful if you want the kiln to string multiple different programs together. For our purposes here, you can use the arrow keys to set this option to None.

Then follow these last steps to start the program:

1. With the full program entered, scroll back by pressing F through each parameter to get to the home screen (actual kiln temperature at the top and current set point temp at the bottom).
2. Press P to move to the Pr G (Program) screen. Be sure to select the number of the program you just created.
3. Press P again, and Run appears. Use the arrow keys to select Yes.
4. Toggle on the Heat Enable switch on the right.
5. “Output” begins to flash on the screen, letting you know the program has begun to run.
6. Let the whole process run and watch the magic happen!

Once your program is complete, you still need to be patient. For your best results, let your glass cool slowly inside the kiln until it reads room temperature (~70 °F).

Then you can take your new glass creation out of the kiln and finish it however you want!

Enjoy Your Kiln Creations

We hope this gives you a solid primer on melting glass in a Hot Shot kiln.

If you have any questions along the way, don’t hesitate to contact our team. We love helping artisans like yourself make amazing things with glass!