Sunday, September 28, 2008

Hollow Lampwork Glass Beads

A hollow bead is made on a regular mandrel by joining two disks of glass. The hot air, which gets trapped inside the glass will make the bead expand. Hollow beads take a bit more concentration than some other types of beads; the more careful you are in each step, the easier it will be to keep your bead shaped well in the end. Always remember to read the heat base and reheat often- the glass in hollow beads is very thin and subject to shocking easily.

There are two ways that hollow beads are generally made. You can build two straight disks, or you can build two conical disks. Generally straight disks seem to be preferred, as it is difficult to keep cones from touching the mandrel, and straight disks can be more easily shaped, manipulated and flattened with tools as you go.

Start by making a small spacer bead at what will eventually be each end of your hollow bead. For your first try, you might place these starter beads about 1/2 to 3/4 inch apart on your mandrel. As you make more hollow beads, you will gain a feel for how far apart to place your disks. Be sure the ends of these spacer beads are nice and even where they touch the mandrel. This will make it easier to have a nicely puckered end on the hollow bead when you are done. Making a spacer bead to start will also help to ensure that your hollow bead adheres well to your mandrel.

Be sure each layer of glass you add adheres well to the layer below it. The glass must be wrapped firmly on the previous layer as you spin the bead. When wrapping the glass, your bead should be slightly behind the flame, while the glass rod is in the flame. Make sure the glass rod is heated all the way through, not just on the bottom, so that you don’t pull the bead around and break the bead release. You may be able to wrap and spin as you go, or you may want to pull a bit of glass off the melting rod and attach it to your disk at regular small intervals. Make sure the layers of glass are adhering all the way around, and there are no gaps between the layers. Continue wrapping the first end until you have a disk about ¼ to ½ inch tall. Then move to the second spacer bead and start your disk the same way.

Remember to keep flashing your whole bead in the flame frequently so that it will not cool too much and break apart.

It can be helpful to use your tweezers or another tool such as flatteners to straighten the disks as you go. You can even out globs, and even make the disks somewhat narrower with your tools. Again, be sure your glass stays warm- reheat immediately after using any tools. Move from the second disk back to the first disk, and build it up some more; then go back to the second disk. Continue in this way until your disks are about ½ to ¾ of an inch tall.

Now it is time to start moving the disks together. Use your marver paddle or brass tool to gently push the two disks towards each other. Make sure the disks are hot at the outside, but cooler near the mandrel- i.e. concentrate your heat more towards the outside of the disks. You want to be able to push the disks so that the outer edges meet, or come fairly close, without moving the glass near the mandrel around. There are several ways make the disks meet. You can get the disks close and bridge them using a hot rod, use tweezers to bring them together, or just push the outer edges of the disks until they’re nearly together. To help to stabilize the disks and keep them from collapsing onto the mandrel, bridging in at least four evenly spaced places around the bead is extremely helpful. In any case, you will need to run a bit of hot glass around the seam between the disks. This will help ensure that you don’t have any thin spots that can blow out later.

Slowly heat the whole bead until it’s glowing. Turn the hot bead in all directions to check for holes. You will need to put a glass patch over any holes you see. You are now ready to round the bead up. Use the heat of the torch and gravity to round up the bead, marvering only lightly as needed. The bead may seem to collapse at first, and then the air trapped inside will puff it up a little.

To gain nice puckered ends on your hollow bead, focus the heat on one half of the bead. Allow the glass to cool and droop down on the mandrel. Let the glass harden somewhat before you move on to the other end and repeat the process.

The hollow bead can now be decorated like any other bead- with dots, lines, raking, even plunging. It can also be shaped, keeping in mind that you don’t want the bead to touch the mandrel other than at the ends. Just remember to reheat often.

When these beads are ready to be taken off the mandrel, I prefer not to soak them. Just pull them off of the mandrel dry and blow out the bead release before cleaning. Once the bead release gets wet, it is much harder to get out of the bead. Be careful not to breathe in the sludge dust as you do this- you should wear a mask. If you'd rather get the sludge wet, you can clean out the excess by blocking one end, filling with water, putting your fingers over both holes, shaking and then blowing it out kind of like an easter egg. Take care not to ingest any of the sludge (yuck).

And now, a a quick look at a hollow in the making:

The oh-so-important footprint and building the disks up on each end, a bit at a time. If necessary, use some tweezers or a flattener to even out these disks. Be sure not to leave holes between the wraps.

See how they start out parallel, and then start getting nudged towards the middle. Your paddle or a brass shaper will help with this. Make sure they don't touch the mandrel!

The bridging begins. And what a mess this one is! Check it for holes, or all your work will be for nothing.

Here it is after just a little bit of time with the paddle. The hot air on the inside helps to blow it out into a nice orb. Keep it moving (but not TOO fast) and gravity will also help with the shape. You can decorate it in any way you like, even plunging works (as long as you don't push too hard with your pick). I started the turtle decoration on this bead by rolling it in a bit of white enamel. One side was flattened somewhat- taking care not to flatten too much, so it didn't touch the mandrel. The rest of the decoration was added, a bit of flame annealing was done to even out the temperature, I annealed it in the kiln, and voila:

A finished hollow sea turtle.