How to Cut and Fire Polish Glass Tubing

Cutting ad Smoothing Glass Tubing Safely

Neon tube cutting and sealing
Ends of glass tubing may be smoothly sealed using a flame.

 James Hardy, Getty Images

Glass tubing is sold in a variety of lengths. Typical lengths are 6" (~150 mm), 12" (~300 mm) although glass is also sold by the foot. There is a good chance you'll need to cut the tubing to make it the right size for your project or experiment, so here is what to do.

Key Takeaways: How to Cut and Fire Polish Glass Tubing

  • Before working with glass, be sure to put on eye protection and thick gloves. If the glass doesn't break cleanly, it can eject shards and cause potentially serious cuts.
  • To cut tubing, score the glass. There are several methods to do this, including the use of a file or glass cutter. Some people prefer to score and break tubing underwater.
  • To break the tubing, either hold the glass near the score mark and tap just below the mark with a hard object or else carefully snap the tubing apart.
  • Fire polish the ends of the tubing by evenly heating the cut edges in a flame. Turn the tubing to assure even heating.
  • Either place the tubing in a container with the hot ends facing upward or else set the tubing on an insulated surface. If you place hot glass on a cold surface (such as metal or stone) it may shatter.
  1. Use the edge of a steel file to score or notch the glass perpendicular to its length. A single score works best. If you saw back and forth, you're asking for a messy break. Also, a light score works better than a deep cut.
  2. Put on eye protection and heavy gloves. If you don't have gloves, you can minimize a chance of being cut by wrapping the tubing in a towel.
  3. Place your thumbs on either side of the notch and apply gentle pressure until the tubing snaps in two.
  4. The ends of the tubing will be extremely sharp, so you'll need to fire polish them before using the tubing. Fire polish the tubing by holding the sharp ends of the glass in the flame of an alcohol lamp or gas burner. Turn the tubing so that it is heated evenly. Stop when the ends are smooth. Be careful that you don't leave the glass in the flame too long, which melts the tubing and may block the ends.
  5. Allow the glass tubing to cool before using it.

If your tubing is too thick or you need to bend it, it's easy to use a flame to bend and draw a glass tube.

3 Easy Ways to Cut Glass Without a File

If you don't have a metal file or a glass cutter tool, don't despair. Here are three simple methods you can use to score and break glass tubing. Again, be sure to wear eye protection and protect your hands with gloves or a towel.

Use String

To use string to cut glass you need rubbing alcohol, a lighter, and a large container of water.

  1. Soak the string in the rubbing alcohol and wring out the excess liquid.
  2. Tightly tie the string around the part of the tubing where you want the cut.
  3. Set fire to the string.
  4. Once the flame completely encircles the glass, plunge it into a bucket of water.
  5. With the glass held under water, hold one side of the string and firmly tap the other below it with a stick or butter knife.

Use Scissors

Tubing will often cut with a pair of scissors. If the edges are jagged (which is likely), fire polish them afterward. You will need scissors, a pen, and a bucket of water.

  1. Use a permanent marker or wax pencil to mark where the tubing is to be cut.
  2. Hold the tubing underwater and simply snip the tubing along the marked line as if you were cutting thick paper.

Use Wire

Using wire to cut tubing it more reliable than string and produces a cleaner cut than scissors. You need wire, a lighter, and a bucket of water. A file is handy but not necessary.

  1. If you have a file, lightly score along the tubing where you want to cut it.
  2. Make sure you're wearing gloves. Heat the middle of the wire in a section long enough to completely encircle the tubing. Be careful because wire conducts heat so even the ends will get hot!
  3. Wrap the hot part of the wire around the tubing.
  4. Immediately immerse the tubing in water. The heat should break the glass without the need to apply any pressure.