Bending a Glass Tube Experiment

The bending a glass tube experiment helps us gain insight into the nature of glass and its innate properties. Glass is a material that is traditionally used for decorative purposes but also as a transparent barrier that allows for relatively safe observation. While many types of glass can be manufactured, we will be dealing with the most standard, commonly manufactured glass which is quite malleable under the influence of heat. Glass is an amorphous, crystalline solid which requires an understanding of handling it with the Bunsen burner in order to bend it successfully without any obstruction or accidental breaking. Here is how the experiment will progress.


To learn, understand, and commit to memory the simple process of the bending a glass tube experiment.

Materials Required: 

One Bunsen burner

One soda-glass tube (20-25cm in length)


  1. Heating tube over bunsen burner

  2. Bending of tube begins due to its own mass

  3. Making sure that the bend and the ends of the glass are all in the same plane (coplanar)


  • Take the soda-glass tube in both hands (holding it by the ends) and hold it over the flame of the Bunsen burner

  • Make sure to focus the heat on one section of the glass tube

  • Rotate the glass tube on its axis using fingers and thumbs in order to ensure that the glass is heated uniformly for proper softening

  • Be certain to know which way the glass tube must be bent once proper softening is achieved

  • The section of the glass that is over the Bunsen burner flame must be red hot in order to perform the next step

  • Gently apply force to the red hot area of the glass tube (it will be softened) in order to bend the glass tube into the desired shape and angle

  • Once the glass has reached the required shape, simply remove the glass from the flame and turn off the Bunsen burner if no one else has a use for it. 

  • Allow the glass to cool by placing it down (be careful to only place it on a glazed tile to avoid damage of surface)

  • The degree of the angles possible through the bending of glass, as well as the conditions for a good and bad bend, are shown in the following diagram.

Precautions to Be Taken:

  • When performing the bending a glass tube experiment, care must be taken to keep fingers at least 4-5 cm away from the Bunsen burner flame and the point of bending of the soda-glass tube.

  • The glass tube should be kept far away from the face and should be held as far from the body as possible.

  • Care must be taken to not try and bend the glass tube by force before it is red hot and soft enough to bend; doing so may break the glass and cause injury.


The glass tube is very brittle and is known to break easily at room temperature. But one can conclude that an amorphous crystalline solid like glass exhibits special properties that allow them to be bent under the effect of intense heat applied to an area. From the bending a glass tube experiment, one can infer that materials like glass have a wide variety of applications specifically because of how malleable it is and how it can be shaped to the desired orientation if heat is applied properly.

FAQ (Frequently Asked Questions)

1. Why Can We Not Bend the Glass Before it's Ready?

The glass is a solid, brittle, amorphous crystalline material and thus cannot be bent in its normal state without breaking. Glass tends to bend at temperatures far below its melting point (at which point it flows like a liquid), but any attempts to bend it before it softens completely will result in an improper bend or even breakage. It’s important to bend the glass gently with as little force as possible since this process uses a delicate tube of soda-glass. Once the glass has softened enough, the red-hot portion will be flexible enough to bend to the desired shape. 

2. What Happens If Red Hot Glass is Placed in Water Instead of a Glazed Tile?

When the glass is in its heated, red-hot state, it is advisable to let it cool slowly on its own. Attempting to speed up the process using water can shatter it and, in some cases, will even shatter it explosively. Thus, it is not advisable to allow any form of moisture next to the glass while it is set down on a glazed tile to cool. Glass expands substantially on heating and thus cooling it suddenly in such a state will result in non-uniform contraction on a molecular level which is what causes it to shatter. 

3. What are the Industrial Applications of Bent Glass?

While glass blowing is a process devoted to the ornamental application, the actual application of bending glass is a cornerstone of any industry that manufactures glass vessels and tubes for practical use. Even in the lab, most glassware apparatus like distillation tubes and U shaped tubes are created through careful application of the process of bending glass. Since glass cannot be bent or shaped under normal conditions, the principle of applying heat is widespread and allows for the widespread creation and manipulation of glass into almost any shape or size that could be required. 

4. What is the Composition of Glass? Can Any Soda Glass Apparatus be Heated and Bent?

Glass it traditionally composed of the following compounds:

Na2SiO3, CaSiO3, 4SiO2 

However, other forms of glass also exist, which may not have the same composition. Glasses of different compositions with different additives will again have specific properties that allow them for use in other industries. Even soda-glass should not be heated and bent again once it has already been molded into an apparatus. This is because once the bonds in the glass are set into shape, reheating them in an attempt to reshape them is ill-advised and typically results in breakage and, in extreme cases, injury.