Forms of Lamp for Paraffin Wax.—Probably, the best form is that devised by Thomas Bolas, and described by him in the Journal of the Society of Arts, December 2nd, 1898. This lamp consists of a small open tray of iron, through which pass three or more flat tubes, and between these tubes are placed small flat pieces of wick, the fit being such that the pieces of wick may be adjusted easily by means of a pair of pointed tweezers.
The flame thus obtained, instead of having one large hollow, is broken or divided so that the combustion is concentrated into a smaller area, and the air blast, which is directed across the flame, carries the flame with it in a more complete manner than is the case with the ordinary flame; a more thorough combustion being realised by this arrangement.
Another advantage is the ease with which the wick may be changed and a larger or smaller wick inserted to suit the flame to any size of air jet.
This form of lamp may be used for oily fuel, although it is specially suitable for paraffin wax.
Two small pieces of bent tin-plate may be used as side covers, and these serve to adjust the flame within certain limits. A tin-plate cover which fits easily over the whole lamp serves as an extinguisher. The complete lamp is shown by d, Fig. 16, and this figure shows also a quick-change air-jet device, the whole arrangement forming a blowpipe for use where a non-gaseous fuel is to be employed.
Although the lamp just described is desirable when complete control over the size of the flame is necessary, and if the ideal conditions and maximum heat are to be obtained, yet a simpler form of lamp will be found to give very good results. Such a lamp may consist of a flat tin tray, having a diameter of about three and a half inches and a depth of about one inch. In this tray is a tin support for the wick, and the wick itself may consist of a bundle of soft cotton, for example, a loosely rolled piece of cotton cloth, but in either case the top of the wick should be cut to approximately the same angle as that at which the blowpipe jet meets the flame.
In using paraffin wax as a fuel, it is necessary to see that sufficient wax reaches the wick to prevent charring during the first few minutes before the bulk of the wax is melted.
Animal and Vegetable Oils.—Almost any oil may be used as a fuel, but many tend to become hard and gummy if allowed to stand in the air for any considerable time. When this happens, the wick becomes clogged and it is impossible to obtain a good flame. A number of the oils tend, also, to produce rather strongly smelling smoke.
A Flame-Guard for Use With Non-Gaseous Fuels.—In order to avoid the eye-strain produced by the luminous base of the flame from a wick burning paraffin wax or oil, it is often advantageous to make a small tunnel of tin-plate, which can be rested on the sides of the lamp and rises over the top of the wick. Such a flame guard is shown by e, Fig. 16.
Small Rods and Tubes from Glass Scrap:—It is scarcely practicable to make small quantities of good glass with the blowpipe flame as the only source of heat, but it is less difficult to make small rods or tubes from glass scrap, and the ability to do this is sometimes of considerable value when a small tube has to be joined on to some special piece of apparatus made of glass of unknown composition. It may be possible to obtain some fragments of similar glass, either from a broken part of the apparatus or from a similar piece, and from these fragments small tubes or rods can be made.