VAPORIZING stoves work on the principle of the paraffin blowlamp. The heating tube has first to be made very hot before vaporization of the fuel will take place. This preparatory operation is done in the following manner. With the air outlet closed, a small quantity of methylated spirit is poured into. The cup at the base of the burner and ignited with a match; this flame plays upon the burner, where the heating tube is doubled upon itself before going to the nipple. By the time the spirit in the cup is nearly burnt out, the tube should be hot enough to vaporize oil passing up to it. The heat of the spirit flame will have warmed up the reservoir somewhat, and so will have set up a pressure within. Normally, by this time some vapour, or some partly vaporized oil, will have emerged from the jet and will have become lighted by the spirit flame. After a few puffs and spurts, a steady roar should come from the burner, and the familiar bluish flame should appear.
In a few moments the flame should become stronger and more regular. Now is the time to give one or two strokes with the pump, but if the flame turns yellow, and spurts of liquid paraffin come out, it is a sign of premature pumping. Open the air outlet valve, to reduce pressure in the reservoir; the flame should then die down. Let the stove cool; fill the cup with methylated spirit and try again. A little experimenting will soon show when to start the pump.
Sometimes the flame, after starting properly, will light-back, and oil will take fire at the nipple; this is a defect due usually to a choked nipple, other things being correct. Avoid spilling methylated spirit over the reservoir; wipe off any surplus before igniting at the cup. Too early operation of the pump may force out liquid paraffin which drops down into the cup, mixes with the spirit, and burns noisily there. Open the air outlet valve momentarily, and the trouble at the nipple should cease; after closing the air valve, the flame should soon start up properly.
The following simple rules should be remembered: 1. Priming. Fill the cup with spirit to about ½ in. from the top, the stove standing on a level surface. Stick to this quantity, and the action of the stove can then be judged. 2. Pumping. Start when the spirit is three-parts consumed; stop at once if liquid paraffin emerges. 3. Air Outlet Valve. Open the valve immediately any irregularity is seen; the flame will then die down. 4. Nipple. Clear this with the proper pricker every time the stove is to be used—before priming and lighting. Do not use any other implement on the nipple which might enlarge the aperture. 5. Filling the Reservoir. Do this only when the stove is ‘out’, and after it has cooled. Do not overfill. About three-quarters full is enough.
General Hints. A full-size stove is better, even for ‘portable’ use, than a miniature one. Px-ocure a proper metal can for the priming spirit, one with a pouring spout. Use a small funnel for filling in paraffin. When buying a stove, get also the following spares: two or three extra nipples; a nipple key for removing the nipples; half a dozen prickers.
The pump can be unscrewed to fit a new leather washer. It may sometimes suffice to bend outwards the sides of the old washer.
Wick-type Oil Stoves
These should not smoke or smell. Defects of this kind are the natural consequences of neglect, and nre usually caused by failure to attend to the wick and those air vents which are intended to allow the passage of an uninterrupted current of air. It should go without saying that the outside of the oil reservoir should be wiped with a dry rag after every filling as a routine precaution against the collection of dirt and dust and the. ~.pread of an oily odour.
In cleaning and preparing for use a paraffin oil heater of a popular type the reservoir should be lifted right out, after the upper part of the stove has been tilted back (a spring catch releases it). The reservoir should then be filled not more than three-quarters full. The opportunity should be taken, at the same time, to trim the wick and clean the burner parts. To get at the wick, the flame spreader must first be removed by twisting, and then lifting. The wick is then wound up to bring its top level with the top of the central tube. Burnt fragments can now be wiped away with a piece of cloth, loose threads snipped off with scissors, and a final gentle patting-down should leave the wick properly trimmed. Scissors should not be used other than for the removal or fluffy bits, unless, through a period of absolute neglect, it becomes essential to restore the end of the wick by cutting it level. The regular removal of loose char should keep the wick in proper condition until it has burned down so short that a new one must be fitted. See arrangement.
Before the reservoir is replaced, the gallery of the heater should be unscrewed (anti-clockwise) and removed for cleaning. A small stiff brush rubbed once or twice over its perforation will dislodge any dirt that may have settled there. When the spreader has been similarly brushed, and any char on its underside scraped off, these parts are in a condition to go back.
In replacing an expended wick by a new one, the latter must be appropriate to the particidar model of stove. After the flame spreader and gallery have been removed, the old wick should be turned up to its limit and then pulled right out along with its carrier. The old wick may then be extracted from the carrier and the new one slipped in, the straight edge of the new wick being inserted into the bottom of the carrier and coaxed upwards. It should finally be pressed against the spikes at top and bottom of the inside of the carrier so that it is gripped firmly.
The wick and carrier are then placed over the central tube and pushed down, the split ends being coaxed into the reservoir and the carrier forced farther down until the teeth on the winder spindle engage with the apertures in the carrier. The new wick having been turned down as far as the winder will carry it, the gallery is then screwed home and the spreader twisted into place. The wick should be given five minutes to soak up oil, when it will be ready for lighting.
It is important to ensure that the carrier is replaced with its top uppermost (the top for a short distance down is unperforated) and that the cogwheel of the winder passes through one of the splits in the wick. Also, it is advisable to dry the new wick thoroughly first. One popular model simplifies wick replacement in that new wicks are purchased together with new carriers.
The wick should always be lighted in two or three places at once, after it has been turned up to the fullest extent (without straining the winder). The heater should then be closed down and the flame turned quite low for a minute or so. That gives the burner a chance to warm up, the flame afterwards being turned on full. Possibility of the heater smoking is then remote. When the flame is to be extinguished it should not be blown out, but the wick turned down as far as the winder will take it. It will be extinguished in a matter of seconds.
Wick economy is practised by ensuring that there is always sufficient oil in the reservoir to prevent the wick burning dry. If the latter should happen, the top ½ in. or more of the wick will have to be rubbed off, with fingers or cloth, and ragged pieces cut away by scissors. Heater models fitted with a damper (a revolving perforated plate at the top) should have this closed, for ordinary purposes. For boiling a kettle or saucepan, the damper should be open. Cleanliness of the exterior of the heater is ensured by rubbing over it occasionally a very little furniture polish, all trace of the latter being then removed with a clean cloth and vigorous rubbing.
The bottom of the central draught tube, the function of which is to allow free circulation of air in the interior of the heater, should not be impeded by the surface on which the stove stands, such as a thick fluffy rug or mat. Ordinarily, the feet will raise it well above a surface, but if it is located on a rug or mat into which the short feet are likely to sink, a square of wood, or other firm and level base, should be provided.
The boiling stove, provided with a grid top plate, requires some care as to adjustment of the flame. Taking a small popular quick boiling model as an example, when this has been lit, the door should be closed securely and the wick turned down very low. After a minute or so it can be turned up, for about the same length of time, to produce a small blue flame. The burner will then have warmed up and the wick can be turned for a larger flame, the maximum flame being blue with white spikes not more than a ½ in. high. It is most important that the wick should not, in any circumstances, be turned up so far that it touches the spreader. Cleaning consists in removing the upper part of the stove (an anti-clockwise turn frees it and permits of its removal), then the flame spreader, freeing this and the burner of char, the latter by brushing across the perforations. With the wick level with the top of the tube, clean this as previously described. Replacement of the wick is effected in the same way as has been described for the heater.
Flame adjustment in the larger model boiling stove is in three stages, low for simmering, medium for ordinary boiling and cooking, high for rapid boiling. The low flame is a small blue one; the medium, blue with white points just showing; the high, for really fierce heat, a blue flame surmounted with 1 in. high white points. The wick, when it requires trimming, should be raised level with the central tube, after collar and spreader have been removed, and wiped level with a soft rag.
It should be noted that this wick is chisel-shaped at the top, the slope being downwards to the inside, and this shape should be so maintained. Lack of frequent attention may result in the top of the wick burning unevenly, wiping with a cloth failing to restore the level. Instead of trying to restore the level with the scissors it is better to empty the reservoir and with all parts replaced, light the wick and let it burn out. The ring of char left at the top can then be removed with the cloth and the top edge of the wick will be level once again.
The oil cooker calls for flame adjustment on the lines of the boiling stove, with the important difference that the high flame may be allowed white points up to 1 in. high but no more. Here, the high flame, which gives intense heat, is only for rapid boiling, frying, and pastry baking. If the flame exceeds that limit, overheating of the burner will gradually produce a still larger flame, and apart from possible dire consequences to whatever is being cooked, smoking may result. A few minutes should always be allowed, with a medium flame, for the burner to warm up.
Daily cleaning of the wicks (to be kept chisel-edged with the aid of the cleaner supplied with the stove) increases the efficiency of the flame . The slotted cleaner is placed on top of the burner tube (after removal of the spreader) and the wick turned up.
As the cleaner is rotated the char is removed and the edge of the wick is left at the correct shape. Airholes in the base of the chimney are likely to become stopped up if a utensil boils over. If that occurs, the chimney should be tilted back and lifted so that the tongue of the cone is freed from the securing collar ring. The chimney being free, the cone (in the chimney’s base) should now be removed and both parts carefully washed in soapy water. The external frame of the cooker should be cleaned with a little soapy water and a cloth, and then wiped quite dry.