"Introduction to Pattern Bars"

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Size and Shape

Next, you have to decide on the size of the pattern bar, keeping in mind that thicker pieces of glass will require longer annealing times. We often think of pattern bars as square in cross section – but they don’t have to be square. They can be rectangular or even round. If the glass is laid up so that it ends up flat, and only ¾-1/2” thick – something we’d just call a fused panel – it can still be cut up and the internal pattern used the same as one would use a pattern bar (see my article in  Glass Craftsman, Issue 212, page 15 of the Batch Insert or link to this page).

Color and Design           

Of course it is necessary to use compatible, fusible glass. Pattern bars can be made of glass which is transparent, opalescent, or a combination. It is important to know how you are going to use the pattern bar slices after you create them to determine which kind or mixture of glasses you are going to need.

 If you want to create a specific pattern it is best to do some planning. The pattern can be nothing more than layers of alternating color – or a complex geometric design. The glass can be placed horizontally, vertically, or a combination of both. Frit and stringers can be incorporated into the design as well. Keep in mind that if you want all the slices of the bar to be identical all strips of glass have to extend from one end of the bar to the other.

For geometric designs it is best to do a detailed drawing first.  One easy way to draw out your design is to use graph paper. If you are using glass that is 1/8” thick – assign each square to be 1/8”. Draw the outside perimeter of the proposed shape of your bar, and then fill in your design. Once this is done, cut strips of glass the length of your pattern bar, and begin assembling. The best way to assemble the pattern bar is directly on the kiln shelf so that you don’t have to move the assembled bar. But, if this is not possible, hold the strips together with Krazy Glue or a similar product so you can move it to the kiln without it coming apart.

A random pattern bar can be created by placing strips of glass in an enclosure without any predetermined pattern in mind. Often some very interesting patterns can be obtained with this technique. Keep in mind that with this technique it can be hard to predict the height of your bar after firing. I’d recommend erring on the side of making your dams too high, rather than too low.

Firing Schedule

Obviously the schedule will depend completely on the size and thickness of the pattern bar, the brand of glass, and the firing characteristics of your particular kiln. But, a typical Pattern bar firing schedule, for approx 1 1/4" thick bars made of Bullseye glass would be:

500 dph to 1500 F Hold 35 min.

AFAP to 960 F, hold 4 hours.

200 dph to 750 F, hold 2 hours.

300 dph to 300 F

Off

Keep in mind that it is perfectly fine to fire multiple bars at once. This will actually save you time and electrical energy and ultimately give you a nice selection of designs to work with

Cutting the Pattern Bars

Slicing up this mass of glass will require a saw of some kind. I use a tile saw with a lapidary blade, but there are other types of water cooled saws that will also work such as a band saw or ring saw – but they may not be as efficient. The main decision to be made before cutting is what thickness you want the slices to be. It helps to know what you are going to create with these slices, how many layers your project will be, whether you plan to fuse the pattern bar slice on a sheet of glass, and whether you plan to cover it with a layer of clear glass. It is very frustrating to find out your slices are too thick or too thin for your intended use.

When cutting the pattern bar, make sure your saw is providing an adequate water spray. Have some sort of guide to ensure each slice is of uniform thickness. Go slowly as you saw through the pattern bar and don’t apply too much pressure – especially at the very end of the cut. You’ll probably get some small chips at the corners of the pattern bar. These can be frustrating, but usually will not render the slice unusable. After cutting it is wise to drop the slice in a bucket of water containing some liquid detergent so that the particulate matter in the tile saw water doesn’t have a chance to dry on the glass until you can clean the slice.

Preparing the Slices for Fusing

In spite of your best efforts, the cross section of the bar may not be perfectly square or rectangular.  A wet belt sander or lapidary wheel is helpful at this stage to grind the edges flat and to smooth out any chips at the corners of the slices. I like to sandblast all surfaces of the slice prior to incorporating it into another project. If you don’t have access to a sandblaster, the slices should be removed from the bucket of water, scrubbed with a toothbrush and rinsed thoroughly before allowing them to dry. This will minimize any haze or devitrification that can appear after the second firing.

The pattern bar slice can be used in numerous ways. They can be placed on top of two layers of sheet glass and allowed to melt into the underlying sheet. This will allow the pattern bar to expand and round out.

Alternatively, the pattern bar slice can be surrounded by layers of glass, which will allow it to maintain its shape and appearance.

Another common way to use pattern bars it to place many of them in an array, one against the other to create a pleasing, repeating pattern. Placing pattern bars in “bookend” fashion can also give some interesting effects. Shuffling these slices around until you get a pleasing pattern is both enjoyable and therapeutic! Once an acceptable pattern is obtained, it can be dammed and fused alone, fused on a sheet of glass as a base, or a border can be added for contrast.

Conclusion

Pattern bars are a fascinating way to add complex designs to kilnformed work. There are some artists who use this exclusively as the major focal point in their work. I hope this article has provided you with enough information to give it a try!