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PATTERN BARS

A pattern bar is a thick bundle of glass that has been fused together to form a solid mass. The size of pattern bars can vary, but most are one or two inches bPattern bar with slicesy about an inch and several inches long. When formed, these bars can be cut into slices with a glass saw, lapidary saw, or trim saw and then re-fused to make unique items.

Pattern bars are related to murrine, mosaic cane developed to its height in Italy and often formed using lampworking techniques. Millefiori ("thousand flowers") are the best known of these canes, which can be sliced and used in fusing projects. If you wish to make similar items using a kiln, the pattern bar methods described in this section will help you get the job done.

 

Cold bundling

This technique, in which strips of glass or stringer are bundled together to form one large pattern bar, works well for simple forms. The glass bundle should be wrapped in fiber paper, then tied together with a high temperature wire (such as nichrome wire) and stood on end in the kiln. Fire to full fuse, then anneal and cool. Because of the thickness of the fused glass, care should be taken not to anneal or cool too quickly.

Stacks of glass strips may also be fused to form pattern bar strips. To maximize the evenness of the strips and minimize the likelihood of distortion dStacks of glass assembled for firing to make pattern barsuring firing, the stacks should be supported by fiber paper, fiber board, and kiln furniture, as illustrated in the photo to the right. This layout allows you to form a large number of patterns bars at one time.

 

Using a stainless steel

A alternative to bundling, this method of making pattern bars involves the use of a stainless steel mold to hold the glass strips. For best results line the mold with fiber paper, then arrange the strips inside, fire, anneal, and cool.Stainless steel pattern bar mold

This approach has several advantages over simple bundling. First, unless carefully prepared the bundled strips have a tendency to deform or even topple over in the kiln. Second, using a mold allows you to use frit and other irregular shapes that can't easily be used when bundling. Finally, the small shape allows it to use space that would otherwise be wasted in a casting or full fuse firing.

 

Using a plaster/silica mold

This technique, which is really a simplified version of kiln casting, involves using a plaster/silica mixture to form a mold for containing the glass to be fused together. Wax is the best substance to be used to form the mold, but other items can be used, including small wood strips.

The section on Kiln Casting (see advanced topics) discusses how to create the model and manufacture the mold. The spaces created by this technique can be filled with strips of glass or frit, then fired to full fuse and annealed and cooled.

When cool, carefully break through the plaster/silica mold. Slice the pattern bars into cross-sections and re-fuse to form a new object.

One advantage of this technique is that round items can easily be made by selecting a round shape to form the hole. Round slices are particularly fascinating to fuse together because they deform and form hexagrams when fused together side by side.

 

Using Styrofoam

This final technique builds on the plaster/silica method by using Styrofoam to form more complicated shapes. Start with a block of Styrofoam the size and shape of the pattern bar you desire. Then cut the Styrofoam lengthwise using a hot wire Styrofoam cutter.Styrofoam cutting tool

Take the two (or more) pieces cut from the Styrofoam and use them as the models to be encased in the plaster/silica mixture. Although they fit together, mold them separately. If you burn out the Styrofoam, you'll be left with a form the shape of the Styrofoam model.

There are several ways to get rid of the Styrofoam. One method is to pour acetone onto the Styrofoam.  This will dissolve it, but care must be taken when handling acetone.  Another procedure is to use a small propane torch to burn out the Styrofoam. You can also use a well-vented kiln (fire to about 1200 F). In either case, avoid inhaling the fumes and make certain you have adequate ventilation.

Once your Styrofoam has been removed, you're ready to fill the remaining form with glass. You can use strips or frit (as in the other types of pattern bars), or you can simply fill each form with a different color of glass.

When you're ready, fire to 1500 to 1550 F, soak until the glass settles (you may want to top up the form), then anneal and cool.

Once the forms are cool, carefully break away the plaster/silica mixture. Slice the bars with your glass saw and fit the shapes together. Re-fuse this assemblage to form a uniquely patterned warm glass object.

Click here to go to the main Advanced Techniques page.

 
 
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