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Combing is the act of drawing a tool across molten glass. It involves opening the kiln at a temperature of around 1700 degrees F,  which make it one of the hottest activities you can do with your kiln. Still, if you take care and follow sensible safety procedures it can be one of the most exciting warm glass activities.


-- Make the combing tool.

The first step to combing is to make the tool you will use to comb. Start with a wooden rod that's at least three feet long. A broom handle or similar stick works well. Get a stainless steel or steel hook (not one made of aluminum, copper, or brass). Screw the hook into one end of the broom. The end of the hook should be straight across, rather than coming to a point.


-- Prepare for combing.

For at least a day prior to combing, soak the wooden rod (hook end down) in a bucket of water. At least a foot of the rod should be down in the water, more if possible. The purpose of this soaking is to help ensure that the heat of the kiln doesn't cause the rod to catch fire.

While you're soaking the wooden rod, prepare the glass to be combed. The easiest kind of arrangement to start with is one that contains narrow strips. Cutting 3/8" thick strips and then laying them on the side works very well. So does using simple strips laid two or three layers high.

One key to good combing is to make sure you have enough glass, so always use at least 1/4" thickness of glass, with 3/8" being preferable.

Arrange the glass strips on the kiln shelf as for a normal firing. Firing on kiln wash tends to work better than firing on shelf paper, but it is possible to fire on shelf paper if desired.


-- Fire to 1700 degrees F.

Begin by firing the strips as for a normal fusing firing. With narrow strips you can heat up very quickly. Keep increasing the temperature until it reaches 1700 degrees F, then soak for a few minutes. At this temperature, the glass glows a very bright red. 


-- Put on your safety gear and get ready.

It's a good idea to wear a long-sleeved cotton shirt, safety glasses that shield your eyes from infrared light, and gloves that can withstand the heat. Put on the safety equipment, then get ready to comb.

You should also remove the combing tool from the water and wipe the metal tip to remove excess moisture and possible contaminants. Keep the water nearby, though, you'll need it later.


-- Turn off the kiln.

It is critical that you turn off the kiln. Never reach into a kiln with the power turned on, especially with a metal-tipped rod in hand. So turn off the kiln, grab your combing rod (shake off any excess water), and open the lid. Be prepared for the gust of extremely hot air that will flow from the kiln.  


-- Comb.

Reach into the kiln with the combing rod, taking care not to hit the sides of the kiln with the tool. Draw the metal tip firmly across the glass. You have to pull hard enough to move the glass, but not so hard that you dig into the kiln shelf. The glass should be soft. If it is difficult for the metal tip to easily make its mark, then close the kiln door, reheat back to 1700 and soak for a while longer before trying again.

To comb properly, the rod should dig slightly into the glass and move through it easily. Be careful not to dig too deeply and go through to the kiln shelf. For a first combing, it's a good idea to draw the rod in a straight line perpendicular to the glass strips. With practice you can draw the rod in more intricate patterns.

Work quickly but carefully. You can usually draw the rod across the glass about twice, then you will need to dip it into the water again to cool off the metal tip. By the time you've made three or four passes the glass may have cooled enough so that combing is difficult.

If this happens and you still want to comb some more, just close the lid of the kiln, turn it back on, and reheat back to 1700 degrees F. Allow the glass to soak for a few minutes at that temperature, then turn off the kiln and comb again.

If you move too slowly or try to comb across the glass too many times, the metal tip may overheat and become stuck to the glass. Don't panic if this happens. Instead, just lift the stick a few inches up. Count to five (to let the glass cool and harden a bit), then twist the rod sharply to one direction. This should break the metal tip loose. Once loose, clean the tip with water and a soft cloth. Allow the glass to reheat to combing temperature, then try again.


-- Finish the firing cycle.

Once you are satisfied with the combing, close the lid and reheat back to 1700 one last time. Soak for a few minutes more (this is to level out any uneven spots in the glass) then flash vent, anneal, and cool. It's a good idea to lengthen your annealing and cooling cycles slightly when firing glass that has been combed or otherwise manipulated.


-- And clean the finished piece.

Sometimes you can complete the combing without picking up too much kiln wash, but at times the kiln wash will be caked onto the glass. If this happens, you'll need to sandblast or otherwise clean the kiln wash from the underside. 

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