In this article, I will discuss some of the basic techniques necessary for lampworking soft glass. Right away I am sure you will notice that these techniques are generally the same for soft glass as they are for hard glass, so I will concentrate on those aspects that are appreciably different. I would like to reiterate that my purpose here is not so much to instruct as to arouse the interest and curiosity of lampworkers in soft glass.
In my last article (part two-beadmaking), I described two techniques that are central to any procedure; point-pulling and shrinking tubing. All of the techniques that follow begin with or are based on the principles of drawing and shrinking. In order to blow a symmetrical bubble, you have to control the application of heat, the concentricity of the tube, and the uniformity of the wall thickness, all while dealing with the downward pull of gravity. It is not unlike juggling. Remember, the heavier the wall thickness, the easier the bubble is to control.
Start with a four or five inch piece of 25mm lead glass tubing on point. Warm it up for fifteen seconds or so in a vigorous pure gas flame. Then dial in a medium oxidizing flame and continue to heat while spinning rapidly to assure uniform heating. Laying down an even "foundation" of heat makes the job much easier later on. Allow the tube to shrink until it just begins to collapse, then restore it to round with a quick puff. Don't blow hard enough to expand the tube or you will defeat the purpose of shrinking. Continue to shrink and puff until the tube is 1/2 to 2/3 of its original volume and uniformly shaped. Adding complex decorations to your bubble will complicate this step, but the principle remains the same. Repeated shrinking and blowing will even out the wall thickness and yield a uniform shape. Ideally, you want an oblate bubble with evenly tapered ends. My good friend Shane Fero takes a somewhat different approach to this part of the procedure. "I do not shrink the tube down to 1/2 its original size. I want it to remain roughly the same diameter, maybe 80% of its original size. I do not usually end up with an oblate bubble, but more often just the shape of the tube." (This disparity in method can be attributed to the difference in skill levels between Shane, a 20 year soft-glass lampworker, and myself, a three year soft glass lampworker. As I said earlier, a heavier wall thickness makes control easier so I shrink to obtain thicker walls. Shane has no such trouble with control so he skips the shrinking and saves time.)
By the way, if you are having trouble with your points collapsing, it may be you need to learn to pull stronger points. Usually, the point can be heated and restored to concentricity with a slight pull.
Now you have a hot bubble and it is time to blow it into the shape you want. Not so fast! Take your time. Have a Look at it first. By continuing to turn it while looking at it from the side you can get a feel for uneveness and let gravity work it out. OK, give it a little puff and check it again. Still even? Good. Give it another little puff and check it again. Isn't that nice? None of the heat and rush of borosilicate glass. You've blown twice now and you've still got time, so blow it again. You should have the bubble to about 90% of its shape and it is getting pretty firm so it is time to make the final blow. Blow more firmly this time and watch the bubble fatten a little more and take on a kind of "tightness". You should now have a nice, round, concentric bubble. The luxury of gradually blowing a bubble little by little is quite useful for those of us with limited experience with soft glass, but to a master, it may not be necessary. Shane adds: "Although I sometimes do this, gradually puffing to get the final shape, mostly I just blow it out in one blow after surface decoration if I just want a round or oblate bubble."(It must be nice to have such perfect control.)
There are many ways to modify the shape of the bubble. If you tip the bubble up or down while you blow you change the direction of the influence of the force of gravity. This will result in bubbles with wider tops or bottoms. After you have blown the initial bubble you can further modify its shape by reheating specific regions of the bubble. For instance, you can take a bubble blown with a wide top and narrow bottom and accentuate that shape by reheating the widest point in a narrow band and pushing it together slightly (like in making a maria). This will result in a bubble with a very sharp, angular shape. You can even do multiple reheating to reshape your initial bubble into almost any concievable form. (see figure 1)
Let's discuss some of these other ways to reshape a bubble. One of the most useful is "ending" or "solidification". The principle behind ending is to finish the closed end of the piece first and to leave a firm handle for working the open end of the piece. First you shape the closed end by heating and drawing (for a tapered end) or blowing (for a rounded end). Then you dial in a small sharp oxidizing flame and carefully shrink the point right where it meets the bubble until the tube becomes solid. Be sure you open both points before you do this and take care that the section you are shrinking conforms to the shape of the end. Also make sure that the point on that end remains exactly concentric. Any little wobbles will mess up the flare at the other end. The result will be an end that has a uniform wall thickness with a small solid area at the tip.
If you are making a bottle or a goblet stem, you will want to use a technique known as "necking". Necking is sort of like pulling a point with the important difference that you want the wall thickness to remain the same. To do that, you must first shrink a narrow section at the top of the bubble to increase the wall thickness. As in "ending" you must take care to conform to the shape of the bubble at that end. Once you have shrunk the neck to the desired wall thickness you slowly draw it until it is the right length. If you have done it correctly the wall thickness in the neck will be the same as it is in the bubble.(see figure 2)
Opening and flaring the end is done exactly the same way in soft glass as it is in borosilicate glass. First, you heat a narrow band right where the point meets the top of the neck or bubble. Then, you quickly blow and draw the point away to create a long, thin bubble that can be easily broken off. Gently knock off any jagged remains. You should have a fairly even end. If you don't, you can pick off any unevenness with a piece of pyrex or snip it off with a small glass shears. Now, heat the end until it begins to shrink and, using a graphite flaring tool, spin the heated end and gently nudge the rim outward. The key to flaring is tapering the heat, not manipulating the tool. More on this later.
If you want a colored lip, you can do what is known as a "lip-wrap". After you have opened, cleaned, and shrunk the end, you apply a thread of colored glass around the lip. Apply it as evenly as possible, but don't be too concerned with getting it perfect because flaring will even the lip-wrap out. Then, flare as before. The color will blend in as the lip flares out. Ideally, the wall thickness at the flare should be about the same as in the neck or the rest of the bubble. (see figure 3)
Opening and flaring a bubble (as in a goblet) is done the same way, but more precision is required than for flaring a neck. You must be sure you start with a symmetrical bubble with consistant wall thickness. Any inconsistancies will be greatly magnified when you do the flare. As in any flare, the shape of the flare is controlled and determined more by the way the heat is applied than by the way the glass or the flaring tool is manipulated. The heat must be gradually tapered, hottest at the lip of the flare, coolest at the apex. You begin by heating the lip until it begins to shrink while spinning steadily back and forth. Use the flaring tool to push the lip out uniformly. Do not exert too much force. Usually the weight of the bubble resting on the flaring tool is more than enough to do the job. As the flare progresses, you will involve more and more of the bubble and so must expand the area of heating. The heat should still remain tapered, hottest at the lip, so you must keep going back to the lip and sweeping the flame down the bubble at a steady speed. Watch the contour of the flare carefully to be sure it conforms to the shape of the rest of the bubble. (see figure 3)
Centrifugal force can be used as a flaring technique, especially for feet. Increasing the speed of the spin will force the hottest part (the lip) outward. However this is a touchy business. The slightest error in heating or inconsistancy in wall thickness or shape will be instantly magnified. Also, spinning your flares will give you almost horizontal lips, something which is OK for feet but may not be desirable for goblet tops. I still do not have the consistant skill level to do spun flares, but I have watched Shane and Fred (Fero and Birkhill) use the technique time and again and never screw up. Shane has even developed his control to where he can do deliberately asymmetrical flares by adding bits of color to the lip in four, five, six, or even seven spots and spinning out feet that have "appendages".
Anything you make out of soft glass, particularly any component parts you make for bottles or goblets, etc. must be flame-annealed. This is nothing more than a thorough soaking in a pure gas flame at the end of the procedure. The length of time required for good annealing varies widely depending on how thick the glass is and how much stress is created when forming the piece. An experienced lampworker can usually just tell when it's annealed, but the rest of us could use some guidelines. One of the best guidelines I have heard comes, again, from my buddy Shane. He taught me to watch how the carbon soot builds up on the piece. When annealing begins, the piece is too hot for carbon to accumulate. But as it cools down to the temperature of the flame, the carbon will begin to build up, gradually coating the piece. As the temperature falls below the annealing point, the carbon will coat the entire piece until it is completely black. This coating provides both a guide to how hot the glass is and insulation to reduce the shock of room temperature.
As in borosilicate glass, one of the greatest advantages in lampworking is the ability to make component parts and assemble them cold. When you want to assemble two pieces, like a goblet top or a bottle to a stem or foot, you simply heat them up again with the same pure gas flame you used for annealing. (I generally will warm up only the end where the seal is to be made but I have watched Shane and Fred casually re-heat the entire piece from dead cold this way).
Obviously, you can't hold hot glass with your fingers so some specialized tools are required to do assemblies. The most important is the flare-holder. This is a grasping tool designed to hold the heated piece from the rim of the flared end. There are several kinds and each has advantages and disadvantages, but the main things to look for in a flare-holder is a handle no more than 8mm thick, a securable method for adjusting the diameter (so it doesn't slip), and good concentricity and balance so it doesn't wobble when spun. You should have several, one for small flares from 1/2 to 1 inch in diameter, one for medium flares from 1 to 3 inches in diameter, and one for larger flares from 3 to 6 inches in diameter. One more thing to remember, if you re-heat a piece from dead cold while it is in the flare-holder, the flare-holder will be heated also and will not shock the glass. However, on occaision you will want to grasp the piece while it is still hot. If the flare-holder is cold, it will crack the piece where it touches it. You must pre-heat the metal grasping tips of the flare-holder before touching it to any hot glass!
Once the pieces to be joined are warmed up, dial in a small, sharp highly oxidizing flame and make the seal using a stem bead or whatever you wish. Make sure you have a good seal. Check for any wrinkles or creases that would create weak spots and fire-polish them out. Double-check the finished piece for concentricity and pop it into the oven for final annealing. One final warning. If you are accustomed to working on graphite plates, be careful not to let a hot piece of soft glass sit on the plate for more than a few seconds. Graphite soaks up heat like a sponge and is capable of shocking the glass enough to crack it! Nothing's worse than losing a piece at the very end of a procedure just as it was about to go in the oven.
Pre-heating, shrinking, drawing, blowing, re-shaping, necking, flaring, annealing and assembling. Master those techniques and you will be able to make anything you can imagine out of soft glass. When you throw in all the different decorating possibilities you can see that there is no end to what can be done. Best of all, you can probably count all the lampworkers in this country who are doing soft glass on your fingers and toes so the field is wide open for exploration. In my next article, I will describe some of the more advanced and unusual surface decoration techniques I have encountered.
Robert A. Mickelsen