Frequently Asked Questions What is fusion? Fusion is the process of heating a material or materials so that separate pieces melt and unite together. What is compatible glass? Two glasses are compatible if they can first be fused together, and after proper cooling to room temperature, have no undue stresses in the finished piece that will lead to fracturing.  The compatibility of a particular glass is a function of both viscosity (resistance to flow) and expansion (change in size as temperature changes).  Two different glasses can be compatible if the viscosity and the expansion are the same, or if a strain caused by a mismatch due to viscosity is canceled out by the strain caused by the mismatch in expansion. The fact that a glass company is making a variety of glass products does not mean that they will be compatible amongst each other. The Thermal expansion of a particular glass can be changed by the addition of metallic oxides, which give the glass its different colors.  Specific compositions need to be mixed for each color of glass to be compatible with each other. What is a compatible clay body? Glass and clay expand when heated and shrink when cooled. When you fuse two pieces of glass, they must shrink at the same rate as they cool or stresses will build up within the piece that may cause the glass to break. During the past several decades glasses have been developed that expand and contract at the same rate. They are said to be compatible.  A manufacture can now produce glass in a variety of colors that react to heat in a similar way and therefore can be successfully fused together allowing artists to produce wonderful art and craft objects. Clay and glass expand and contract at much different rates when heated and cooled.  However, up until now, they have never been successfully fused together. What is the difference between glass and glaze?   Although pottery glazes are true glass, glazes are meant to be applied as a thin coating on the surface of the pottery.  To hold their position on the surface of the pottery; they must be quite stiff when melted.  The type of glass used in fusing is fairly runny when molten and it is applied mainly in the form of cut sheets.  Glazes are made by blending the un-melted, raw materials and spreading these blended materials on the surface of pottery, where the glaze is melted into place.  Glass, on the other hand, is melted first in a pot of molten liquid material and then fashioned into objects and sheets.  A glaze on the surface of pottery is in slight compression.  This means that there is stress on the surface of ordinary pottery.  If you were to make the glaze thicker the stress would be too great, and cause crackling of the glaze and in extreme situations cracking of the pottery. What is a clay body?   A clay body is a combination of clays and other earthy minerals that are blended together for specific purpose.  What John Groth has done, is develop a clay body that expands and contracts when heated and cooled at the same rate as glass. When the clay and glass are fused together there are no undue stresses that will separate the composite or cause it to fracture. Can John’s clay body be used with various types of glass?   Since different glasses behave in their own ways, John has developed special clay bodies to be used with various glasses. Where do you make your fused clay and glass pieces? A new 5000 square foot facility has been constructed to house his glass studio.  This is where the glass and the clay body are fused, shaped and slumped. The studio has eight kilns ranging in size of one cubic foot to forty five cubic feet, with the largest kiln capable of handling a sheet of glass up to 72 x 30 inches in size.  The glass studio also houses the cold working equipment for grinding, polishing and sand blasting.  The adjacent 2000 square foot studio contains the clay mixing facilities, an area for working clay, and the Waterjet cutting department. Can fusible clay be used like any other clay?   Fusible clay, when wet, is plastic and can be manipulated by a number of traditional clay forming techniques: coiling, slab building, throwing on the potters wheel, pushed, pressed, crumbled, poured combed, pinched, rolled, cut, are just a few of the multitude of techniques possible.  As long as the clay is not fired, it can be re-wet, mixed, and used over. How is the clay fused to glass?    In a kiln, the clay body can be fused to glass in one firing.  Moreover, the clay can be bisked first and then fused with glass in a second firing.  Once fired, the clay becomes a hardened ceramic and will hold its shape, texture or modeling when fused to glass.  This ability of the fusible clay to hold its shape when fused, is the most exciting aspect of this new material.  Glass, when molten, will try to maintain a thickness of 1/4 of an inch because of surface tension.  The structural qualities of the clay can be used to, contain the fluid glass, add dimension, depth, and texture.  Clay components can protrude out of, into, and in-between the glass.   What else can you make with the fused clay and glass?   The possibilities provided by the combination of the two materials only limited by your imagination.  Some of the applications are: sculpture and unique vessels, windows with clay texture that allow light to pass through while providing privacy at the same time, table tops, room dividers, backsplashes, wall panels, screens, cabinet door inserts, and cabinet knobs. What is the texturing process?   Texturing of the glass is done by applying our moist clay body using special tools and techniques. The clay is then allowed to dry on the glass. When the textured glass panels are heated to fusing temperatures, the glass will flow into and around the textured clay application. The texturing can be thin, like a film, where it is translucent, or thick like coils of one centimeter or more. Texturing can be on top of, in-between, or underneath the glass. What the glass/ceramic sheet process?   Glass/ceramic sheets are composed in the kiln by adding layers and colors of fusible glass and/or clay and firing them to fuse between 1350 - 1650 degrees Fahrenheit. The firing and annealing can take as little as 24 hours and up to several days or more, depending on the thickness of the product. Very thick slabs of glass can take weeks to cool.  The standard sheet of glass produced is 35 x 20 inches and 1/4 inch thick, although larger and/or thicker sheets are possible.   Can you cut and fuse the glass more than once?    Fused sheets of glass, or clay the glass composite can be cut by hand or with our Waterjet machine, which can cut the glass into virtually any desired shape.  Cut shapes and clay elements can be refused into new compositions.  New layers of glass, or clay, can be added and fused to provide shape color and texture. Some seemingly simple compositions may require up to a week or more in the combined re-firing processes. What is annealing?   Annealing is the process used to relive stress in glass during cooling.  This is accomplished by maintaining a consistent temperature through the entire body of glass.  The glass is held at a temperature just below the temperature at which that specific glass will start to move due to heat.  Heat is transmitted very slowly through glass, so the glass has to be held at the annealing temperature anywhere from an hour to days or weeks.  The annealing process is dependant upon the thickness of the glass.   The glass is then brought down in temperature while maintaining a consistent temperature throughout the body of glass.  The cooling time also depends on the thickness of the glass; the thicker the glass the slower it will loose heat from its center.  When the kiln cools down faster than that which is required by the thickness of the glass, heat is applied to the top or bottom of the glass to maintain a consistent cooling gradient throughout the body of glass.   Stresses caused by incompatibility of glasses can not and will not be relieved by annealing, and will remain when cooled. Can you blow the glass fused with the clay?   “Roll-up” is the technique of pre-fusing a sheet of glass and then reheating it to a temperature where the glass becomes fluid enough to allow it to be picked up with a moil, (a hot sticky cookie of glass on the end of a traditional blowpipe).  The hot fused sheet of glass is rolled up around the end of the moil on the blowpipe and closed off in to a bubble.  The fused glass can then be blown with traditional glass blowing techniques using a glory hole (a blast furnace used to heat the glass to workable temperatures).  The fusible clay has proven to withstand the intense heat and repeated hot working and reheating required in the blowing process.  The fusible clay provides a new element in the visually exciting dance of the glass blower in the midst of flames, heat, and smoke. What is hot working?   Hot working is the method used to manipulate and form hot molten glass with tools, paddles, blow pipes and punties (rods to hold, move, and spin the hot glass shape or vessel while it is being worked and reheated).  Hot working techniques with the fusible clay include: blowing, wrapping of the molten glass around the clay, draping, pulling and free manipulation out side of the kiln or furnace.  The fused clay and glass can also be manipulated within the fusing kiln by opening the kiln and grabbing, pushing, and lifting the hot glass with tools.  Kevlar gloves, hoods, and face shields are used as necessary to provide shielding from the intense heat. What is cold working? Cold working is the work done to the glass in ambient room temprature.  Grinding, sandblasting, and polishing are the more common cold working processes.  When glass is ground or polished, excessive heat is generated due to friction.  Friction from grinding the surface of the glass can generate enough heat to crack the glass, so the glass is kept cool with running water. What other processes are used to make and finish your work? Slumping is done by firing the glass pieces which are placed on top of a mold, or shape.  By heating the glass to a temperature hot enough for the glass to move the Glass/Ceramic assumes the shape of the mold by slumping into, or over it.  Dishes, trays, light fixtures and other shapes are created this way. What is Waterjet cutting?   Waterjet cutting is the technique by which we cut the sheets of glass/ceramic into tiles, and other desired shapes. A stream of water under immense pressure, forty thousand pounds per square inch, passes through a pin size hole in a sapphire and then picks up grains of garnet which acts as an abrasive. This computer driven high pressure stream of water will cut almost any material into virtually any imaginable shape. This also allows us to do fine inlay work. How can I attach or support the fused elements?   Support and fixture for interior or exterior fixation to buildings can be produced within the fused glass composite.  Mounting holes or notches can be made in and through the panels.  Textured clay on the fixation surface of glass/ceramic tiles facilitate