Glaskolben is the name for a pre-blown clear glass cylinder with a blow pipe end, used for blowing glass balls or 3 dimensional shapes. It is the same product used throughout Europe for making Christmas tree ornaments.
Blowing an ornament with Glaskolben is easy. However, it takes practice to get the feel of the glass as it softens in the flame.
Light the torch and adjust the flame back from a sharp point. A broader flame is better. Select a Sealed End Cylinder and introduce it into the back of the flame i.e. away from the torch. Rotate it as it is brought into the hotter area of the flame.Continue to rotate until the cylinder is glowing red and starts to reduce in size or collapse. However, do not let the neck end of the cylinder get as red or the cylinder will be hard to manipulate.
Remove it from the flame, held vertically, then give it a quick snap to align the cylinder. Blow steadily into the blowpipe end to a full ball, while rotating. (See illustration.)This is where you must “get the feel of the glass”.
Overblowing can cause a blow out.The ball must be annealed at this point. See separate annealing instructions.
ELONGATED BLOWN SHAPE
To make an elongated shape follow the same procedure as in blowing a ball. Rotate the cylinder in the flame until it starts to glow a red color. Then use tweezers to pull the end as far as desired while blowing and rotating. Immediately put the ornament in an annealer.
Annealing is the process whereby we toughen brittle glass by heating and slow cooling. Each manufacturer’s glass may have a different annealing range. In the case of the Glaskolben, the annealing temperature is 950°F [510°C]. There are different methods of annealing:
Placing a blown shape deep in a container of vermiculite warmed on a hot plate, serves well. However, care must be taken to be sure that the red glow has faded before placing it in Vermiculite. Otherwise, it may stick to the glass.
Move the glass shape out of the hot area of the flame [blue color] and in the yellow range for 2 to 5 minutes to allow it to slowly cool and anneal.
This is the most reliable method. The kiln control can be set for the desired annealing temperature and run for twenty minutes or more. The amount of time after 20 minutes makes no difference. One cannot
over anneal. Leave product in kiln to cool slowly.
REMOVING THE BLOWPIPE END
After the ornament has annealed the blowpipe end can be removed. The best method is using a Carbide scoring tool. With this tool in one hand and the ornament in the other: press the sharp side of the carbide steel against the blowpipe neck and the thumb of the same hand pressing against the other side, rotate the shape while scoring the neck. Still holding the ornament, tap the blowpipe end to break it off. An ornament cap can be placed on the ornament to finish it off. Don’t discard the cutoff neck! It may be decorated to make a stylized bell, etc.