|
|
Artwork that is turned inside-out has special properties when done with borosilicate glass. Because of the lower
C.O.E. (co-efficiency of expansion), borosilicate glass “hugs” itself when it is heated. This phenomenon creates a pattern of thermal differences (hot and cold spots).
Recently, technical artists and artwork theorists have developed many ways to achieve a magnified inner surface. Of the various methods available for creating magnified borosilicate artwork, the “teacup” method is one of the most commonly used, as it can be a bit more forgiving than other styles; it also requires less effort and physical endurance than many of the more intricate and decorative artworks that are produced by the professional lampworking artist.
Other techniques for achieving a magnified canvas include: “Snip and Flip” (the tube is art worked then turned physically inside-out through the process of cutting and re-fusing); “Flared” (a tube is opened up on the end and prepared much the same as the described method in this article. This is a simple method, yet disallows any accuracy with patterns or designs laid into the glass); “Stuff and Puff” (this method is very striking, but requires extensive experience to pull it off without a hitch. A bubble of color is stuffed inside of a semi-flared, goblet-shaped receptacle and then blown out).
As the variety of ways in which artists achieve these effects has increased, so has the number of individuals who are inspired by them. The “inside-out” technique can be incorporated with other techniques to form new and previously unknown views of colored borosilicate (Shot A and B). These techniques provide an exquisite foundation for the future of lampworking, and have been instrumental in the expansion of contemporary technique.
WHAT YOU NEED:
1. 22 mm heavy wall tube. This can be pulled into two separate points. Some artists will use the raw “ends” of the tube that are left over from pulling points out of a new tube. This can be a quick method of making “teacup” style pieces, as the open ends are heated and flared without as much preparation. The trade-off, however, is that the artwork tends to be disproportionate, and requires extensive removal of “pasties” (for those of you not familiar with this term, it is the sludge,
devitrification, and dirt that was produced when the glass was sheared).
2. 3mm rods. These rods will be used to apply a coating over the metals that are fumed onto the inner wall of the tube. These applications will gain depth as they become “one” with the inner wall.
3. A preparation of your favorite fuming metals (gold and/or silver). A detailed description of using metals is outlined in Bandhu Dunham’s Contemporary Lampworking 3rd Edition regarding “fuming” and safety practices associated with its use. For artists interested in an alternative to fuming with pure metals, there are several colors produced by Glass Alchemy (my favorite fuming color- Blush 182) and Northstar (my choice would be Caramel NS-44) that will release fume when heated, and these can produce some very wild effects, so the fuming possibilities are endless.
4. Optional blowhose assembly (not displayed in this demonstration). This can be very useful when doing several different inflations throughout a piece, and can also remove any inhalation hazards that may be associated with this process.
5. A collection of thin color rods. These can be applied to the inner wall of the tube, and should be used sparingly for this process, as too much color added to the inner wall will upset the balance of the materials and cause disproportionate melting to occur.
6. One graphite rod (any size under 5/8 of an inch will work). This rod is useful for marvering the inner wall of the tube after the artwork has been melted in. This can help to smooth out the inner surface before you attach the second point. You also want to pre-make an open-ended 22mm point that is flared out to about 1 ¼” to attach to the tube that will contain the artwork. For this demonstration of the “teacup” method, this is the way in which the tubing is sealed and blown before the piece is finished. This can be made using the description outlined here for making the inner tube canvas for the artwork that is applied to the inside of the tubing, only omit the artwork and hold in the kiln until it is needed.
For sealing the molten artwork before the piece is inflated, a small section of 25 mm rod can be used instead of the tubing, and can yield effects that are just as breathtaking. However, the solid rod method works in plugging only a point that is open. For the process outlined here, we will use points that remain sealed until it is time to stick them (the “teacups”) together, at which time one of the points will be open just prior to joining the two. By doing this, we minimize the amount of moisture that can collect inside the tube during the art working and/or fuming process.
In Dunham’s Contemporary Lampwork-ing 3rd Edition, there is a wealth of information explaining many of the techniques described within this article. His book is by far the most complete resource on the subject of lampworking, and contains references and pictorial demonstrations of even some of the most obscure techniques.
THE INNER TUBE CANVAS
We begin by pulling a three-inch point out of a length of 22mm heavy wall tubing. An essential part of any tubing work is a well-aligned set of points on both ends of the tube. A piece that is created off-axis is ultimately changed completely by a lack of balance, and stained by an informal symmetry. With this particular process, a straight set of points will largely influence the success of the process. Since we are using centripetal force to flare the glass in portions of this project, a well-aligned point is necessary.
In the next step, we heat the right portion of the tube, roughly about two inches from the right point transition. This will leave a cooler section of about an inch on the left side of the tube.
As the glass begins to soften, slowly make a transition from holding the point level (0 degrees) to holding the point at a 45-degree angle, keeping in mind that the glass needs to be flowing towards the cooler portion of the tube. Make the tube angle up with the hottest portion of glass flowing downward.
As glass collects at the cooler side of the point, pay attention to the axis that is holding it. Be sure that it does not get heat sufficient to cause it to wobble. Heating only the surface of the tube can help to move the glass while keeping the desired shape. Be sure to maintain even rotation while melting the surface towards the cooler axis.
After a few moments, the glass will get much thicker on the cooler portion of the tube. When it reaches a thickness that will suffice in flaring a saucer for the artwork, then it is time to blow into the tube. Elevate the point above your mouth (unless you are using a blow-hose assembly), maintaining the position used in thickening, with the tube up at an angle.
Gently blow into the point until the tubing has formed a graduated funnel shape, much like a hot air balloon with no curves (Shot 2). Once this cools, open up the thin end of the tube as much as you would a goblet. Then flare the end slightly. You want to be sure that you left the seal on the end of the thickened point. This prevents moisture from collecting on the inner tube, avoiding breakage.
Finish the flare into a disk-shaped opening to expose the inner wall of the tubing. This can most easily be achieved by using centripetal force, which will give the flare exceptional consistency, letting the lip of the flare retain a great deal of heat. Spin it to push the glass outward in a circular pattern (Shot 3).
Holding the tube with the flared open end towards you, fume any precious metals onto the inside lip of the tubing. Try to cover the entire inside surface of the tube (Shot 4).
Add clear dots, or whatever is appropriate, to the inside lip with a 3mm rod. Be cautious not to burn off the precious metals before applying the clear (Shot 5).
Also, try to avoid “stacking” clear or color in your applications, as this will make melting much easier, and it will be less likely to create stresses that compromise the integrity of the piece. Small amounts of color can be added to accentuate the dimensionality of the reverse image (Shot 6).
Using an extremely oxidizing flame, focus the heat directly on applications in the inner lip. Use increased care not to allow the inner hole to close completely. The graphite rod can be used at this point to smooth out any lumps that remain, as well as prepare the lip to match the pre-made lip. The point tip of the pre-made flare should be cut off, and the flare should be ready to be applied (Shot 7).
Allow the piece to cool slightly; then heat the edge of the lip allowing the glass to “flow” towards the open hole. Don’t allow the hole to close. Attach the prepared flared tube to the open flare on the end of the piece (Shot 8). The attached point should be pre-heated, but slightly cool. The area that the two “saucers” are joining should be as hot as possible, to allow for a smooth fusing of the two.
Blow immediately into the piece while pulling slightly to even out the wall. Then make the piece molten and blow again (Shot 1). The more you do this, the stronger the piece will be. From here, shape the piece as you wish (Shot 9).
Chris Chorvat is the owner of Murinni Art Glass, Spokane, Washington. He teaches glass workshops through the Spokane Art School as well as through private channels to both beginning and advanced students. He gives demonstrations to city and public schools and is published in Bandhu Dunham’s new “Contemporary Lampworking”. He is a founder of the Inland Northwest Glass Guild.
Bibliography: Contemporary Lampworking - A Guide to Shaping Glass in the Flame. Third Edition-2002, Bandhu Dunham, Salusa Glassworks, Prescott, Arizona.
|
|
|
