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So, what's on the agenda this glass-blowing lesson? How about making large circles, border tubes, multiple outline units and bubbles. Your glass bending experience to date should help make these lessons a manageable and fun task.

The Big O The Big O or Large Circle is a challenging glass exercise. Because the curve is so slight on a circle three feet or larger in diameter, the tube cannot be heated as molten as usual. Too hot a tube sags with gravity more than indicated on the pattern.

Because the tube is heated so slight, strain usually develops within the glass structure, strain that eventually leads to breakage. You make a cut on your perfect curve and a split begins traveling around your masterpiece. Sometimes the split travels the full length of the curve ruining your effort. What to do?

There are a couple solutions. One is to heat the glass to molten and allow it to sag excessively with gravity. Just prior to exiting the flame, flip the tube over so you have a second or two to get the tube to the pattern before it sags too much. You can pull on the tube slightly to remove excess sag also.

At the pattern, make certain straight tubing remains tangent to the curve. That is, no straight tubing runs along the curve, it stays outside it. The extra heating reduces chance of strain and by remaining tangent to the curve, chances of flat spots or wobbles are diminished.

Another solution is to flame anneal the tube. Many craftsmen return the tube to the flame after forming the curve and after the glass has setup a moment. They heat the curve backside a few seconds to slow the cooling rate. This effectively reduces chance of strain. But even this method requires practice so expect some disappointments.

Don't make very large circles from a single tube. Break them up into segments to ease bending, tube processing and handling. And don't be afraid to use a jig, a piece of curved wood or even tiny nails driven around the pattern. Many craftsmen use jigs to speed up production.

Neon Border Tubes Border tubes are simply tubes that border something: usually a building, window or wall. The challenge making them is the border tube needs to be extremely straight and the tube ends must be accurately formed.

Border tube electrodes often are connected so they align head-on or side-by-side requiring a high degree of accuracy when forming. With some fixed insulators, improperly aligned electrodes result in breakage during installation. So, getting the bends right the first time saves everyone a little grief.

Practice making border tube ends using two to three inch pieces of sealed scrap clear tubing. Using scrap glass will save expense over using real electrodes potentially destroyed during practice. Weld them on in a cross- or cannon fire. This will aid your skills for the next maneuver, forming the connecting bend.

Most border tubes run about eight feet to twelve feet in length. Since glass tubes commonly are four-feet in length, this means you'll be making plenty of very straight welds.

To aid keeping the tube straight, align it over a straight line drawn directly on the bending table. Some prefer to eyeball the tube straight and other craftsman build a jig to keep it aligned while they weld with a handtorch. Any method practical for you is the right method.

Double Outline Bending double outline letters or designs offers unique challenges. But for the most part, double outline is easier to bend than most specialty letter styles.

Planning is most important so, remember the first rule of bending: bend the inside first then bend outward. The rule still holds true with one additional observation. Look for a basic bend, an L-bend, U-bend or Offset that you can save out of sequence for folding a complicated piece together.

Folding a double outline piece together using a saved basic bend is a powerful tool that will save you both time and frustration. It will save time because you won't need to make so many cuts and welds. It will save frustration because you'll be more productive and produce a more attractive product.

Consider Figure 1. It shows how saving one L-bend and rotating the tube ninety degrees moves previous work out of the way and allows work to continue unobstructed. The saved L-bend is used later to fold the piece together.

Sometimes it is useful to save more than one bend out of sequence; it always depends upon the design. But by choosing to save easy to form basic bends, you increase your chance of success.

Channel Letters Channel Letters are big multiple outline letters. They're used to illuminate plastic or metal cans made in the shape of letters or designs.

Channel letters tubes are bent much the same as double outline letters except that they are usually made of larger diameter tubing. Large diameter tubes offer less electrical resistance than do small diameter tubes. So, any given transformer can drive more linear tubing.

Manufacturing a tube that runs much more than ten to fifteen linear feet is difficult to process and unwieldy to handle. So, break multiple outline designs into smaller, more manageable segments and make your work and that of other's less demanding.

Glass Bubbles You won't find much use for glass bubbles in conventional neon signs but you might in neon artwork. Be aware that large glass bubbles light much more dimly than the rest of a tube because light spreads across the surface decreasing light density.

It's always important to gather glass before blowing into a bubble. This helps maintain glass wall thickness. See Figure 2 for tips on blowing various neon bubbles and go blow for fun.

Add these bending skills to your bag of tricks and you'll find any new glass challenge obtainable. But since most every project is unique, you'll also discover there is a little something to learn with each new venture. Next in this series, tube processing-lighting your glass masterpiece.