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The formulas and techniques in this section have been derived from many different sources. Credit has been given where it is known, but in many cases the originator of the formula remains anonymous.

Please be very careful when handling or mixing chemicals and make every effort to follow proper safety procedures.  You can find more information on safety procedures in the Health and Safety section of this website.

Click below to go to the section you are interested in.


DEVIT SPRAY (Borax/water solution)

Purpose: To prevent or minimize devitrification

How to use: Spray or brush lightly on top surface of glass prior to slump firing.  

Ingredients: 1 teaspoon borax to one cup water. Distilled water works best. Regular borax cleaning powder (such as the "20 Mule Team brand" in the US) works well. Precise measurement not required.

Safety precautions: Don't drink. Wash hands after using. Long term exposure to borax can be harmful.

How to make: Just mix the borax with the water. If you put the two ingredients in a small glass jar with a lid, then cover and shake, you'll be assured of a good mixture and have a place to store the solution, too. Label the jar. Shake again prior to each use.

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Purpose: To prevent glass from sticking to the kiln shelf or mold.

How to use: Spray or brush lightly on shelf or mold. Allow to dry thoroughly before firing.

Ingredients: The most basic formula uses equal parts of kaolin and alumina hydrate. Pottery suppliers generally carry these ingredients.

Safety precautions: Wash hands immediately after using. Wear gloves if you are sensitive. Powder can be harmful to lungs, so mix with caution. Wear respirator if you are sensitive.

How to make: Mix kaolin and alumina hydrate together. To this powder you should add four to six parts water until desired consistency is reached. Store in a tightly covered glass jar. Label the jar and shake well before using.

Additional tip: You can pre-mix kaolin and alumina hydrate and store the powder in an airtight glass jar. Then you just add water when you're ready to use the kiln wash.

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Caution: This process can be hazardous. Do not attempt it without appropriate safety equipment and ventilation.

Purpose: To produce an iridized surface on the glass. Glass iridized with a stannous chloride solution will not lose its iridescence at fusing temperatures.

How to use: Spray solution on glass at fusing temperature.

Ingredients: Stannous chloride crystals, muriatic acid, distilled water. Muriatic acid, also used to clean brickwork or increase the acidity of water, is available at hardware or swimming pool supply stores. Stannous chloride is more difficult to find, but is stocked by some ceramic/pottery suppliers.

Safety precautions: Both muriatic acid and stannous chloride can be hazardous. Wear complete safety equipment, including a respirator and gloves. This process creates significant fuming, so kilns should be well ventilated. Care should also be taken to minimize overspray from the solution onto floors and other surfaces.

How to make: Use equal parts muriatic acid and stannous chloride and from two to three parts water. Place the crystals in a glass jar and add the muriatic acid. Add the water and mix the solution thoroughly. The amount of water required can vary depending on the kind of sprayer used. Start with two parts and increase as necessary.

Use a glass sprayer. Plastic may melt in the heat of the kiln and the acid will corrode metal. Heat the glass until the temperature is around 1500 degrees Fahrenheit. Turn off the kiln, and spray the solution on the glass. Use a fine mist.

After applying, close the kiln and heat for a few moments. Then cool and anneal as normal.

Additional note: This formula and technique was adapted from Boyce Lundstrom's Advanced Fusing Techniques.

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Frit is nothing more than small pieces of glass. Generally, they are sorted by size and used in a variety of ways, the most common of which are kiln casting, pate de verre, or as a design element on sheet glass.   

The easiest way to obtain your own frit is to buy it. Tested compatible frit is available from both Bullseye and Uroboros. It comes in a number of different sizes, ranging from powder to chunks as large as 1/4" (6 mm).   

If you want to make your own frit, there are a number of techniques. Several are described below.

Using a hammer

For this approach, place the glass to be used between several pieces of newspaper and strike with a hammer until the pieces reach the desired size. This method is crude but effective. Make sure you wear eye protection. Wear a mask if significant dust is produced.

Tack fusing

Place the glass in the kiln. One arrangement that works well is to heap smaller chips of glass on a larger sheet. Heat until the glass tack fuses around 1400 degrees F. Once the glass has fused, turn off the kiln, remove the glass (use gloves and tongs steel fireplace tongs work well), and drop immediately into a bucket about 2/3 full of cold water. The shock will crack the glass into many small pieces. Glass broken this way will be in relatively large chunks. If you want finer pieces, you can use the hammer technique described above to break it down some more.

Melting in a crucible

This technique requires more caution than the first two. Place the glass in a crucible, a ceramic container made for withstanding the heat of the kiln. Heat it to around 1700 degrees and soak to allow the glass to melt.

Then turn off the kiln and use tongs to remove the crucible. (Wear gloves and eye protection and take special care.) Slowly pour the molten glass into a bucket of cold water. The glass will break into finer particles than in the tack fuse approach discusses above. Make sure you return the crucible to the kiln and let it cool slowly to prevent thermal shock.


Obtain two hollow pipes, one slightly larger in diameter than the other so that one pipe fits inside the other. Close off one end of the smaller pipe, fill it with rocks or similar heavy items, then close off the other end.

Now place the larger pipe upright on a hard surface like cement and fill it part of the way with the glass you want to break. Slide the smaller, heavy pipe into the larger one, letting it drop full force onto the glass. (You will probably need a second person to help you hold the larger pipe.) Raise the smaller pipe and drop again and again until you are satisfied with the size of the particles. If you use this technique, wear eye protection and a mask or respirator to protect you from the silica dust. Also, you may want to use a magnet to extract any metal chips that may be caught in the frit.

Frit-making machines

It is possible to buy frit-making machines, called "glass crushers." Alternatively, you can rig up your own machine using a garbage disposal, heavy duty blender, or similar item. Boyce Lundstrom's Advanced Fusing Techniques describes a crusher built from an old garbage disposal and a large steel drum. Kervin and Fenton's Pate de Verre and Kiln Casting of Glass also has information about building your own frit machine.

If you make your own frit, you will probably want to separate it into sizes and store it in jars or plastic bags until needed. You can separate the glass manually or you can use wire mesh screens, which are available from ceramic supply stores.

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Although the resulting stringer will probably not be as perfectly formed as those made commercially, making your own stringer can be accomplished in two different ways.

The first involves traditional lampworking techniques. Cut a strip of glass about 1/4" wide and 10" long. Grab one end of the glass with a pair of pliers and heat the other end in your flame. Heat until the end becomes molten and starts to ball up. Then quickly grab the molten in with a second pair of pliers and stretch the glass to form the stringer.

This technique takes practice, but after a few attempts you should be able to form longer and longer threads. If you do not have access to a lampworking setup, you can use a propane torch (relatively inexpensive and commonly available at hardware stores) .

A second technique involves the use of a kiln and a crucible. Place glass frit or chunks in the crucible and heat until molten. This will likely require a temperature of approximately 2000 degrees F, which may be beyond the capability of your kiln.

Once the glass is molten, turn the kiln off and use a metal rod to reach into the crucible and remove some glass. A 1/4" steel bar works well. With the glass on the end of the bar, marver the glass on a metal or graphite surface. (Marvering simply means to roll the glass until it become smoother and forms a nicely shaped bar.)

Once marvered, return the metal rod to the crucible and pick up some more glass. Marver a second time, rotating the rod to keep the glass from falling off the end.

Now have a second person grab the molten glass with a pair of pliers and slowly walk away from where you are holding the rod. It may take some practice to learn the correct pace for walking away. Too slow and the stringer will be short and fat. Too fast and it will be too brittle. But if you walk at the right pace the glass will stretch into a long stringer.

This process can be repeated as many times as necessary to use up the glass and form the desired stringer.

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Confetti (also known as shards), paper-thin slices of glass generally used as design elements, are most frequently made using glassblowing techniques, but they can also be made in the kiln.

There are several ways to use your kiln to make confetti, but all are based on the concept of slumping glass until the stretched sides become very thin. To achieve the necessary thinness, it's generally necessary to suspend the glass high in the kiln and allow it to slump and stretch until it reaches the floor. When the glass cools, the thin sections of the glass can be broken into shards and used in future fusing projects.

The simplest way to make kiln-formed confetti is to use a drop ring. By supporting the ring high in the kiln and allowing the glass to slump beyond the point of forming a simple vase, the sides very thin. When the glass cools, they can be broken in shards.

One consequence of the drop ring technique is that the confetti has highly curved sides. If this is a problem, you could make a square drop ring to lessen the curvature, or you could make the confetti by stretching nichrome or other heat-resistant wires across a metal frame constructed in your kiln. By laying a sheet of glass across the wires and then slumping, the sides of the stretched glass will be very thin. When the glass cools, they can be broken into nearly flat shards that can be used in future fusing projects.

Although the colors of the confetti made in this fashion are sometimes not as intense as the colors of commercially available shards, starting with tested compatible glass virtually guarantees compatibility, so that confetti can be layered heavily if your design dictates.

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