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close this bookGATE - 2/88 - 10 years GATE (GTZ GATE; 1988; 44 pages)
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How to make glasses out of old bottles

by Hans Schmidt

Sections of bottles have many popular uses. They can be used as drinking glasses, as containers for pencils, vases for flowers and, last not least, even as beakers for experiments not involving heating.

This is then moistened thoroughly, but not so much that the paper drips. The strips are then wrapped around the bottle two or three times with the fold facing the notch, and about 0.5 cm from it. The end can be secured with a piece of string or a pin. It is very important that the glass

In "gate" 2/87 (p. 24 and 25) a method of producing cleanly, evenly cut edges was described. Bottles and other hollow glass bodies can be cut for the above-mentioned purposes using even simpler methods. While the cut edges are not always satisfactorily smooth, this method is safe, cheap and instructive, and thus particularly suitable for schoolchildren.

Cutting with a flame

First, using a triangular file, a thin notch of about half a finger-width (1 cm) is filed into the convex edge of a bottle. The notch must be filed in a straight line corresponding to the direction in which the glass is to crack. For this purpose, it is best first of all to mark the notch with a felt-tip pen, and to lay the bottle on a non-slip surface while filing. Following this' two approx. 4 cm wide strips of newspaper are folded in the middle so that you have a clean fold and a double strip roughly 2 cm wide between the newspaper strip and the notch remains dry. The notch is then held steadily in the tip of the flame of an alcohol burner or candle for between 15 and 30 seconds, depending on the thickness of the glass. Then, turning the bottle slowly, the rest of the glass between the newspaper strip and the level of the notch is heated up. The bottle has to be turned two to three times in all, after which the notch is heated until the glass audibly cracks. The crack starts at the notch and continues all round the bottle. If this is not immediately successful, a drop of cold water on the notch will help. Gentle tapping of the notch with a blunt object will help to continue the crack all round the bottle.


The individual steps in cutting glass with a flame

This method is based on the principle of creating hot and cold zones adjacent to one another in the glass. The expansion of the hot zone and its rapid cooling by the drop of water lead to tensions in the glass, causing a crack along the line determined by the notch. The method is simple and works after a little practice.

Even better results can be achieved if, using the same procedure as above, the glass is heated with the fine flame of a blow pipe (see below). In this case, the damp strips of paper are not needed. The edges of the glass are smoothed with glass-paper or a fine file.

Blow pipe

To make this, the metal cartridge of a ball-point pen is burned out over a cool flame, after which it is cleaned with a fine wire. The ball is removed from the cartridge with a pair of pliers and the resulting aperture widened a little with a fine needle. The plastic tube of an infusion bottle will fit on to the cartridge. Caution: to avoid infection, used injection needles must be baked thoroughly, and plastic tubes sterilized for a sufficiently long period.


The metal cartridge of a ball pen is burned out at low temperature


A plastic tube as used on infusion bottles fits on the cartridge. The glass and jars made from the bottles can be used for many different purposes. All drawings: Hans Schmidt

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