Cutting Glass Tube and Glass Rod

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Cutting Glass Rod

An inorganic non-metallic material that does not have a crystalline structure is glass. These materials are said to be amorphous and are virtually solid liquids cooled at such a rate that crystals have not been able to form. For cutting a glass rod take a glass rod. Place it on a table. Hold it firmly and make a single deep scratch with a triangular file. Place the scratch and put the thumbs on each side of the scratch at equal distances from it and start applying pressure and then give a quick bending motion until it breaks smoothly. 


Cutting Glass Tube

On the glass tube or rod, the scratch should be made in one single stroke. Do not use a file like a saw. It should always be moved in a backward direction. On the tube, do not press the file to such an extent that the tube may smash. In breaking the glass tube with mild pressure if there will be a difficulty then put another scratch. For a very long time, do not keep the edges of the tube in the flame, otherwise, the end will be sealed. So, the steps required to cut the glass tube are:-

1.Entire tubing is in contact with the top of the table, place the glass tubing on the table like that only.

2. With the help of markers make a small mark on the tubing at the desired length.

3. With the help of a triangular file on the mark, keeping the tubing pressed on the table with the left-hand makes a deep scratch on the glass tube at the desired length. So that file should be at right angles to the glass tubing.

4. Hold the tube with both hands on the opposite sides of the scratch such that one thumb is on either side of the scratch. It will always be on the side away from you.

Now slightly press the tube with the thumbs. The tube will break from scratch.

5.  It may cut the finger or hand if touched because the tube has sharp edges  therefore, it needs to be rounded off as follows:

(a) To remove the sharp splints rub the edges with wire gauze.

(b) Keeping the tube rotating, place the ends in the flame of the Bunsen burner. 

(c) Take it out of the flame, as soon as the edges start becoming red hot.

(d) Place it on an asbestos sheet for cooling.

By firmly bending the tube away from yourself break the glass- pushing with your thumbs against the cut glass. This should produce a nice, clean-cut. 


How To Cut Glass Rod

1) At the top of the table, place a glass rod such that the whole area of the glass is in contact with the top of the table.

2) With the help of a marker, make a small mark on the glass rod at the desired length. With the help of a triangular file on the mark, make a deep scratch mark on the glass rod keeping the rod pressed on the table with your left hand. The glass rod should always be at the right angles to file.

3) Then, hold the above rod with both hands such that one thumb is on the opposite side of the scratch but either side of the scratch. Now, the scratch will be on the side away from you. Now slightly press the rod with the thumbs. The rod will break at scratch.

FAQ (Frequently Asked Questions)

1. What Precautions Must be Taken When Doing a Cutting Glass Experiment or Any Other Laboratory Experiment?

  • Have goggles and apron on before any chemicals or equipment come to your lab station.

  • Always point the test tube away from yourself and other students while shaking or heating a test tube containing chemicals.

  • Never taste any substance in the laboratory. Do not eat or drink from laboratory glassware. Do not eat or drink in the laboratory.

  • Between the glass and the flame, heat flasks or beakers on a ring stand with wire gauze.

  • In a well-ventilated room or under a fume hood use flammable liquids and they also in very small amounts.

  • Always, in a single stroke, try to make a single deep scratch of the required length.

2. Why is a Glass Tube Rotated While Heating in a Burner?

It is important to rotate the glass tube with one stroke of the file, to make a single deep scratch at the desired length. This is to be done to ensure that all sides are being heated properly because of uneven thermal expansion this avoids cracking. It should be rotated in such an order to ensure uniform heating. Forcefully, never bend the glass tube. By doing so you can break the tubing. Lastly, do not heat the end for a long time. It may seal the end or make it narrow so that is why the glass tube is rotated while heating in a burner.