Boring a Cork

A cork borer is often used in a Biology or Chemistry laboratory. It is a metal tool used for cutting a hole in a rubber or cork stopper to insert the glass tubing. Usually, the cork borers are available in a nested size set including a solid pin, used to push the removed cork or rubber out of the borer. In general, the individual borer is called a hollow tube, tapered at the edge, with some handle on the other end.

Cork Borer Explained

A Cork borer sharpener is a separate device used to hone the cutting edge to slice the cork more easily.

These cork borers are also used for tree ring analysis (dendrochronology), taking samples from living trees, and taking samples for experiments when a constant diameter is required. For example, a cork borer is used to maintain a constant surface area when testing the potato's water potential.

A cork borer can also be used to punch holes on an agar plate and perform well diffusion assays to study bioactivity in microbiology.

Let us observe the process of boring a Cork.

Boring a Cork

In the chemical laboratory, the student must carry out simple operations such as cutting a glass tube, bending a glass tube, boring a cork, and the complex process of analyzing substances both qualitatively and quantitatively. Thus, a general acquaintance with such operations becomes obvious before taking up the actual experiments. As most of these processes involved heating, and hence, knowledge of using a burner is essential.

Aim

To learn the basic techniques on boring a cork and fitting the glass tubes.

Required Materials

• Water

• Cork

• Cork Borer

• Glass Tube

• Cork Presser

Lab Procedure

Let us discuss how the process goes through.

Softening the cork

A cork becomes harder over time and tries to bore a cork, which hardens results in the formation of cracks. To soften the cork, we are required to wet the cork in water. Once the cork gets flexible, press it in a cork presser, which is a mechanical device. In another way, we can wrap the wet cork in a piece of paper and place it under the shoe, and press it. Now, we have softened the cork.

Boring the cork

Place the cork on a flat surface area or a table with its narrow end facing up.  To ensure that we get a straight hole, mark the borer position on both sides of the cork. If the cork that we have taken is a rubber one, we can apply some glycerine to the borer. The reason we do this is that glycerine acts as a lubricant on the hard rubber cork. Now, hold the cork with the left hand tightly, and by applying force, start the boring process with a twisting motion. You should make sure the borer throughout remains vertical.  Take the borer out and reverse the cork when half of the cork has been bored. Now, start boring from the reversed or opposite side till a hole is obtained. Finally, now, we can remove the borer.

Fitting a glass tube in the bore

Now, we will fit the glass tube into the hole bored in the cork. Then, dip the end of the cork through which the tube will be inserted in water. Perform the same with the end of the tube that is to be used. This process ensures the easy insertion of the tube into the cork. Hold the cork with the help of one hand and the tube with the other. Then, hold the tube close to the wet end and insert it into the cork's borehole using a rotatory motion.

Note: To fit up a wash bottle, it is essential to bore two holes in the cork. The two holes are bored similarly as done for a single hole, but we should consider the precaution that the two holes should not be very close to each other. If there is a minimal distance, then the thin cork layer may result in a break.

Precautions

Let us look at the necessary precautions that are to be followed while performing the procedure:

• Select diameter bores slightly smaller in size than that of the tube to be inserted in the hole.

• Create a mark on both sides of the cork

• For obtaining a smooth hole, drill half the hole from one side and the other half from the cork's other side.

• Since the rubber is a hard material, usually, the end of the tube inserted is dipped in glycerine or caustic soda solution before fitting it in the hole.

• The glass tube should be rotated to ensure uniform heating while heating.

• Do not bend the glass tubing by force ever. The tubing may break if we did 

Applications of boring a Cork

• Wash Bottle

A wash bottle is an apparatus used in science laboratories. It is a container in which distilled water is taken for conducting experiments. A wash bottle produces a fine stream of water that can be utilised for washing away precipitate residues. For most procedures, a flat-bottom flask of volume equal to 500 ml is taken. A cork with two bores is fitted into this flask. Two tubes are fitted into the bores. One tube is bent at an angle of 120° while the other tube is bent at 60°. On blowing out air through one tube, we see that water comes out from the end of the other tube with considerable force. 

Other Basic Laboratory Techniques

Cutting a Glass Tube

Cutting a glass tube is an important procedure that one must know. It is required for making U-shaped tubes and other such delivery tubes. You ought to know how to cut a glass tube without sustaining an injury. Follow the steps listed below to do this properly:

• Select a glass tube that is devoid of any cracks.

• Hold the tube firmly and make one deep scratch on its surface using a triangular file. Do not apply too much pressure or the tube can break.

• Place your thumbs on either side of the crack. Apply gentle pressure so that the tube breaks smoothly without leaving any jarred edges. 

• If the ends of the tube are not smooth, smoothen them by rotating the ends in a flame for 2-3 minutes. 

Bending a Glass Tube

This is another common procedure students should familiarise themselves with by following the steps listed below:

• Hold the glass tube carefully between your thumb and finger.  Slowly heat each section of the tube in the flame of the burner. Keep rotating the tube till it softens.

• Apply gentle pressure to the tube so that it bends under its weight. When this is done, remove the tube from the flame of the burner. 

• Take an asbestos sheet and place the bent tube on it. Press it gently to make the tube coplanar.

• Allow the tube to cool for a few minutes. 

Drawing a Glass Jet

To complete the process of drawing a glass jet:

• Take a delivery tube of the required dimensions. Hold it with both hands and place it on the flame of the burner.

• Keep rotating the tube to ensure uniform heating.

• Continue heating the tube till it softens completely.

• Now, apply some pressure and gently pull the two ends apart. The middle portion should ideally come out to be about 2 mm.

• Let the tube cool for some time.

• Now, cut the narrow portion of the tube with a triangular file. This will help you obtain two jets. Smooth the edges of the jets by heating them on a flame for some time.