I've not posted on this excellent Forum for a while now, but the recent acquisition and restoration of a pre-war Famos 120CP mantle lamp has caused me to look again at the light output from various pressure and non-pressure mantle lamps. And, again, I am having difficulty reconciling the figures. Armed with my trusty Avo Model 2 foot-candle light meter, held exactly 12" away from the light source and on the same horizontal level, and some working lamps, I have obtained the following readings of candle-power: Wax candle - 1 CP (so far, so good...) Famos wick lamp with Aladdin 60CP mantle - 60 CP (still so far, so good...) Tilley TL136, rated at 300CP - 125 CP (er...) Electric 100 watt tungsten light bulb - 125 CP So the Tilley, which is fully restored, fully pumped and as bright as any other "300CP" pressure lamp that I've ever seen, is only really emitting 125CP. This seems to confirm measurements reported by others, as well as anecdotal reports that it is impossible to get the rated output from a Tilley. I have seen comments that the manufacturers were able to back up their claimed light output with detailed measurements, but does anyone have access to this data? My experience is that light output from a pressure lamp depends largely on the mantle. I'm willing to believe that thoriated mantles would have given much more light output than today's offerings, but could a non-thoriated mantle account for a 50% drop? All suggestions and comments will be welcome! Kind regards, Phil
Hello Phil, the light output from a Tilley depends mainly on the condition of the vapouriser and the burner and the type of mantle. If the vapouriser and burner on a Tilley are the older types and they are unused and a thorium mantle is fitted, then the light output will be better. That's a fine looking Famos!
Indeed it is... I think we still have a similar issue today with the ratings of low energy light bulbs where I'm yet to be convinced that any of them are half as bright as they claim and that after half hour waiting for the things to "warm up".
Compact Flourescent Lamps (CFL's) vary in their ability to brighten from cold, but all contain mercury vapour one of the most dangerous toxins on the planet hence the need for specialist disposal. They also give off ElectroMagnetic Fields (as do mobile phones, over head power cabling, wi-fi, etc.) that are harmful to the body and brain. Switch to LED bulbs - they are full brightness from cold and less harmful. The downside is initial cost, but they consume less power than CFL's. Steering slightly back to the thread !! Lumens is the measure of illuminance, whereas candlepower is the measure of radiated light. Over to this lot for clarification!
Many electrical items radiate, one of the most well known is the emission of an RF signal from TVs and computer monitors. Sometimes referred to as 'Van Eck Phreaking' - Link . In military security, it is known as 'The Tempest Threat' - Link I remember attending a demonstration at a UK base where a boffin tuned in to and displayed the screen from a computer located 50m away on a £20.00 B&W TV bought in Woolworths. The phenomenon is used as the basis for the UK TV license detector vans. So if you want to shield your TV from the vans, put it in a Faraday cage . Funny how topics wander Terry
I'm not quite sure of the relevance of the last posting...! But I agree that the measurement of light output from a bulb or similar source can be confusing. However, the 'powers-that-be' have decreed that all light bulbs from now on are to be rated in lumens, so it makes sense to be able to convert readily between candlepower and lumens in order to compare our vintage lamps with present day units of measurement. I have come across the conversion factor 12.57 in several places, and this is based on the fact that one candlepower = 1/683 Watts per steradian, assuming the light source radiates equally in all directions and there being 12.57 steradians in a sphere. Hence 1 candlepower = 12.57 lumens. This ignores the fact that most vintage lamps do not distribute light equally in all directions. Returning to my earlier figures, the Tilley lamp produced 125 candlepower, equating to just under 1,600 lumens, almost exactly the same figure as a 100 Watt tungsten lamp. The link to the mantle experiments that dspearsy quoted was fascinating, and certainly explains the discrepancy between the manufacturers' claimed 300CP (with brand-new burner and thoriated mantle) and the figures around half that, which we seem to get in practice. Thanks for everyone's input - things are a little clearer now Phil
To add to the discussion: A number of internet sources say that CP cannot be calculated to Watts. However Petromax specifies the following performance in Watt: HK/CP 500: 400 Watt HK/CP 350: 280 Watt HK/CP 250: 200 Watt HK/CP 150: 120 Watt From the same web site: Personally I find this overrated: I have 2x 88 Watt light bulbs (Energy savers, corrected output 88 Watt) in my living room and they sure give more light output than my Petromax 350CP 8) Cheers, Peter
Very interesting, Peter - that's exactly what I calculated from my light meter measurements, 1 Watt equals 1.25 candlepower. The "watts" in this case being the rating of an incandescent light bulb of equivalent brightness, based on the typical performance of tungsten filament lamps. The relationship only holds for mantle lamps too, so should be used with caution, but for our purposes it's probably quite accurate. You may also have seen Camping Gaz LPG mantle lamps marketed as "80 watt" lamps, so other manufacturers as well as Petromax have found this to be a useful comparator. I suppose the "tungsten watt" is more familiar to modern consumers than the "candle" in terms of the brightness of a light source! Phil
125cp from a Tilley is not bad. I have seen plenty at around 80cp and only a very few at over 150. You need to rotate a tungsten bulb because the filament is a coiled line so it radiates different readings depending on presentation. I measured a 100w bulb at 114cp side on and 175cp full on. Your 125 is in the range so will be correct. To get true readings you need to eliminate reflected light but your readings are in the right range so can be relied on as reasonably accurate. I had to learn to trust the meter so that once you get readings for known lights such as a candle or a 60 cp mantle lamp you know the results are good and then you can see just how different the actual and rated power of pressure lamps can be. ::Neil::
I guess it is in order to yet again bring forth that old post about Neils photometer. Or the McRae-Graff Photometer, if you like. It's [url=http://0flo.com/index.php?threads/3223 and it's interesting reading.
It is actually wrong to quote a lamp light output in watts. The figures are not really all that far out when compared to standard tungsten filament light bulbs but light power does not translate to watts because they are measuring different things. For instance a Tilley actually produces around 1.25KWh and that figure is pretty stable BUT most of that 1.25KW is heat and only a small amount is light. As far as I know only Petromax gave light output as watts and that was almost certainly an attempt to give a number that customers might understand. Plenty of people know what a light bulb looks like but very few understand candle power so perhaps it is a reasonable marketing figure. However we are not casual users but specialists and we should use the correct terms to measure our lamps. The manufacturers were pretty casual with cp figures anyway. An old Petromax was rated at 500HK and in later years they changed that to 500cp but 500HK is actually just over 450cp so unless they changed the burners one of those figures had to be wrong. Coleman used to rate all their product but some years ago decided this was not helpful because customers did not really understand the term. ::Neil::
I'm with Coleman on this one. As far as I can see, there are only three light intensities worth considering which are:- bright, not bright enough and too bright. Anything else is just a waste of time and effort. Your mileage may vary...
Hi Neil and thanks for the information. Where do you get your 1.25kW figure from, by the way? All the figures I have calculated suggest a heat output of around 750 watts from a 300CP Tilley lamp, based on the stated burning time of 12 hours on 1.5 pints of paraffin with a calorific value of 46.2MJ/kg, or 10.2kWh/litre. As an engineer interested in energy conversion, I was simply keen to check that my measurements of candlepower were correct, and I'm glad that Neil seems to think they are. One of the interesting outcomes of my calculations is that the Tilley pressure lamp is much more efficient than the Famos wick/mantle lamp in converting paraffin into light. The Tilley gives out 2.15 lumens per watt, compared to the wick/mantle lamp's 0.76 lumens per watt. These incandescent mantle lamps were the best and brightest lighting technology available at the time; they compared favourably with the humble candle at 0.16 lumens per watt, but were eclipsed by the tungsten light bulb's 16 lumens per watt. Phil
I haven't been able to find a figure quoted anywhere, which is why I calculated it from first principles - can you advise where the 1kW figure is quoted, please?
Ah perhaps you might think so but actually this is historically not so. The incandescent mantle dates from about 1896 ish and both wick fed and pressure mantle lamps were developed concurrently from that time. Pressure was always more efficient and generally brighter for a given fuel consumption if perhaps initially rather less reliable. By 1900 the pressure guys were talking about 800cp lamps and the best any wick mantle lamp ever did was 120 and that was later anyway. Why wick feed lamps developed and improved in the face of an overwhelming superiority in power and efficiency I don't know. I suspect the answer is as much social as anything else. Maybe folk just liked the quieter lamps and perhaps saw them as easier to work with and maintain and of course the wick lamp had been around for a long time before the mantle so folk were familiar with them and therefore prefered to stay with the technology they were happy with. Also some fuel suppliers gave away free lamps in order to sell fuel and the lamp makers generally improved the engineering they were familiar with although some such as the German guys Petromax and Hasag made and sold both wick and pressure lamps for a long time after 1900. Another mistake people make is to compare mantle lamps with electric. However up until around the 1920s most electric light bulbs were poor things which did not give anywhere near the light output of a good wick mantle lamp and certainly could not compete with a 300cp pressure lamp. The only really bright electric lamps were arc types and then were never suitable for indoor domestic use. Light bulbs only got to be good and reliable with the introduction of a metal filament. The early bamboo and carbon filaments were weak and unreliable. I really can't remember where that 1.25KWh came from. I always assumed it was about right because of the heating effect a 300cp lamp gave into a room. I know in the winter of 1966 we used a pair of FL6 lamps for heat and they were more than enough for a big high ceiling living room. ::Neil::
Perhaps it was mere simplicity of use as well as the lack of noise and brilliance (maybe eyes more used to wick lamps were more capable of seeing things in such a light), along with the need of a secondary fuel to pre-heat, and then pump up. We are all very used to a quantity of light emitted from electric lights nowadays, and most folk would spurn messing about with paraffin and matches, let alone getting hung up on the 'eco' thing. Once a habit is lost it's hard to return to it when the sheer convenience of flicking a switch does away with fetching, storing, refuelling, replacing and trimming wicks etc. There may also be the not so good experiences of flare ups when lighting from cold. Inexperience and poor practices amount to bad news, and that always travels fastest. In an outdoor environment was possibly where many pressure lamps won their well deserved place. Though that is a loose hypothesis considering the number of fine table lamps available. Perhaps when the energy 'crisis' bites minds will turn. Better stock up!
Good question, Phil - it was quoted on the Tilley website but when I looked last evening, the history section there had been drastically trimmed. I seem to recall it was also quoted on the Vapalux website but I haven't checked that one yet given it's completely changed from the Bairstow Bros. (1985) Ltd. version. But trust me, it is/was the generally quoted figure - perhaps some of the old-timers will recall it too...
Thanks for that, David. I can't find any mention of it in Jim Dick's book either. I calculated the heat output simply from the calorific value of paraffin and the fuel usage rate for a 300cp lamp. A 500cp lamp would of course give proportionally more heat, around 1.25kW, so perhaps that's where the figure comes from. The relationship works out at 2.5 watts of heat per candlepower. Thanks also Neil for the history information, very interesting indeed because as you can tell, I am a newcomer to wick mantle lamps. I must confess to being impressed by them, though; quick and easy to light and completely silent, together with no noticeable odour when running, unlike pressure lamps that do put out a very slight although not unpleasant aroma. As Derek suggests, perhaps the pressure lamp remained king for robust outdoor applications where noise and heat were less of a problem, leaving the wick mantle lamp for indoor duty? I am grateful for being allowed to let this discussion stray into the 'wick' arena because I know there are some strong views held about non-pressure lamps! Phil
The dreaded CFL produces electronic 'hash' from some kind of an oscillator. I know the damn things radiate all sorts of garbage that renders a nearby radio useless. They should come with Schaffner filters to keep the RFI out of the mains. Wheras a (whatever favourite pressure lantern) only produces ultrasonic sound from the vapouriser that will possibly annoy bats. I recall that a Coleman milspec '252' was a particularly bad culprit. I earned more than a few 'black looks' after lighting up mine at a Bat Group meeting. Or was it also due to its tendency to smoke like a Kuwaiti oil-well fire if you were careless with the lighting procedure. Was a bit 'smelly' too on 'unleaded'. This was long before I wised up and started using Panel Wipe. Mr McRae has always noted that Tilley pressure lanterns do not appear to produce their stated output. I have a Tilley TL136 & representative Bialladdin 300X. They both seemed to produce 'enough' light. The party trick of the Bialladdin is that it will not only keep me warm but can heat a kettle without too much difficulty. It is the old version with the brass hood to which I added a brass ashtray as a heat-deflector. Something I believe American Gas Machine made a feature of with a 'convertible' lantern/stove. Old electric light bulbs were not always a 'coiled-coil but a hairspring single strand of whatever. It's as fine as a hair. This bulb could be 1920s - 1930s as it has a visible 'pip' where the envelope was pumped.
