CONVERT OLD LIGHT BULBS INTO CHEMICAL GLASSWARE (Nov, 1933)
How TO CONVERT OLD ELECTRIC LIGHT BULBS INTO CHEMICAL GLASSWARE
By Earl D Hay
EXPERIMENTS in an amateur chemical laboratory are much more interesting when they are made with the same kind of apparatus as that used in professional laboratories. As a rule, however, the home chemist experiences a great – shortage of flasks and endeavors to use various kinds of bottles as makeshifts, little realizing that he may make from burned-out electric light bulbs a great variety of useful flasks like those sold by chemical supply houses at from 20 to 75 cents each. The lamps used in the average home vary in size from 25 to 200 watts and are suitable for small Florence or boiling flasks. Larger flasks are made from 300-, 500-, and 1,000-watt lamps, which can be obtained from the janitors of stores and linemen of the city lighting companies.
The methods of working all sizes are the same, and only a few minutes are required to complete a flask.
The method of making a Florence flask washing bottle from a 300- or 500-watt lamp will be described. The flat bottom is made first. Cut off the connection of the center wire on the cap with a knife and break off the end of the slender tube which was used in evacuating the bulb when it was made. This is necessary in order to equalize the air pressure on both sides of the glass wall. Next screw the light into a drop-cord socket to provide a handle for holding the bulb while the large end is being heated over a large laboratory gas burner or a gasoline blowtorch.
The bottom of the bulb is carefully warmed up and then heated evenly to a light red color. Now quickly place it in a vertical position on a level wooden block or an asbestos pad and bear down gently. The spherical bulb will flatten on the bottom. If heated too hot, the bulb will wrinkle and become distorted; if not heated enough, too much pressure will be required and the bulb will be broken.
After the bulb has cooled sufficiently to be handled, remove the brass cap from the neck by filing through the threads on a diagonal line as shown in one of the photographs in order not to scratch the glass with the file. Pull the split cap off with a pair of pliers, and scrape off the sealing wax that lies between the brass cap and the glass, taking care not to destroy the two copper wires leading into the center of the bulb.
As the bulb becomes quite hot while the neck is being shaped, it is necessary to provide some adequate means of holding it. If a pair of heavy asbestos mittens are not at hand, a satisfactory holder can be made from a piece of strong cloth by cutting a round hole in it large enough to admit the neck of the bulb. The neck is inserted through the hole, and the cloth folded back over the bulb.
The end of the bulb neck is now carefully heated until the glass becomes red and plastic. With a pair of pliers, seize the two copper wires and carefully remove the glass core by pulling straight out on the wires as the bulb is rotated in the flame to keep the entire circumference at the same temperature.
Next take a round, soft pine stick with a conical point and begin to open up the mouth of the neck and roll a bead on it by rotating the neck in the gas flame and rubbing the plastic edge out and down with the wooden stick. This enlarging process is continued until the neck will take the desired size of cork or rubber stopper.
The flask is now complete and ready for use. If it is to be used for a washing bottle, a heavy rubber band or stout cord wound around the neck will make it much stronger in resisting the stopper pressure and more convenient to handle.
If the bulb is to be made into a boiling or a receiving flask, the bottom will not need to be flattened, and the brass top may be removed and the throat enlarged to the proper size at once. If a heavy smooth lip is desired, it can be made by making a mold of some heat-resisting material as shown in the drawings at the end of this article, and the lip turned down against it. This mold or form must be made in halves and clamped around the neck of the bulb. It must be warmed carefully before use, otherwise the glass will crack.
If a lipless flask is desired, the small end may be removed by placing a string saturated with kerosene around the neck and allowing it to burn away, then quickly plunging the neck into water up to the heated ring. This will cause the glass to contract and pop off at the line where it was heated. The broken edge is then smoothed by carefully grinding it down on a smooth grinding wheel and finishing it with a fine sharpening stone.
If a glass-tube cutter is available, the end of the neck can be removed without difficulty. This method is more reliable than the use of the kerosene string.
Long-necked flasks may be made by welding test tubes or necks from broken flasks to the necks of light bulbs. After a little practice this can be accomplished without difficulty. First be sure the ends to be joined are of the same diameter and fit all way around. This can be accomplished by grinding the ends on a smooth oilstone. Heat the ends carefully and evenly in the gas flame until plastic; then bring them into contact and exert a slight pressure.
FOR A DISTILLING flask, it will be necessary to weld a tube to the neck of one of the larger flasks at a downward, angle of approximately 75 deg. to the neck. A hole is first made about halfway down the neck of the flask by heating the side of the neck to a red heat over the gas burner and then punching the hole from the inside by using a redhot wire with a right-angled hook on the end. A piece of tube of the desired bore and length should be selected, and the free end heated sufficiently to smooth off the sharp edges. The end to be welded to the flask is next heated and flanged. This flange is turned out at a right angle to the tube and should extend about 1/8 in. all the way around it. The neck of the flask and the tube are next brought to a welding heat in the same flame; then the tube is carefully centered over the hole in the flask and the two gently pressed together. Very little pressure can be used or the flask will become distorted. The joint is now heated quite hot and the flange gently smoothed down to make the joint stronger and neater in appearance. In doing this, be careful to support both tube and flask or they will tend to sag out of shape.
AFTER the joint has been completed, the hot flask should be placed in a heated oven and allowed to cool very slowly. This will temper the glass and remove the strains set up in the welding operation. If all the flasks are given the hot-oven cure, they will be less liable to crack in use, especially when heated over a gas flame.
Sometimes the necks are cracked because of careless heating. If carefully cut off, the lower halves of such bulbs make transparent covers and shallow dishes.