I know how they work–the flames come up past a couple of cement logs or something. Is there something impregnated in the cement that gives that picturesque yellow flame?
No real answers, just some speculation. The different color of the flames could be caused by different temperatures. Those blue flames on the stove are much hotter than typical fireplace flames (whether gas or real wood logs). The logs could also have chemicals to make the flames that color. I remember as a kid having stuff to put in our fireplace to make the flames different colors.
As to the “painted” logs – the link references a “six step painting process”, which could include some type of baking like with enamel. In fact, they probably use enamel paint.
The stove is designe to burn “hot”, because after all, it’s to cook with. Also, hot water tanks, grills and heaters, when running correctly, should burn with blue flames.
Blue is indicative of a good burn, focusing energy in one spot for the purpose of cooking/heating a specific area. Some chemist will get on hear and tell you more about that, but in the home, blue flames are a sign of a good hot burn.
Gas fireplaces are more ornamental than anything else. Sure you might scavenge some heat, but they are decorations primarily. The burner isn’t designed to cook anything, but rather be bright enough and big enough to have an ornamental effect. Relative to the paint and the ceramic logs, the fire isn’t all that hot.
Why doesn’t the paint on the logs burn? Why doesn’t the paint on an engine burn? They are both designed to handle the heat. Most paints like this are already dark in color and are usually pretty “flat” in color.
Some fires work by having the flame heat a (usually) ceramic material which then radiates heat. In mine the flames start off blue but turn red/yellow when the ceramic starts to glow red hot. Perhaps the effect is to do with the radiated light passing through the flames.
A: Yeah, engines are painted. Blue and Orange, among other colors. Ford is mostly blue, and Chevy is/was mostly orange.
B. For the record, my fireplace and stove are both gas, and both are burning blue right now. You will get orange/yellow streaks everyone once in awhile, but I’ve always attributed that to dust or lint being kicked up into it. Could always have it checked if you get paranoid.
Also note that if multiple colors where present, the yellow would be higher, “on top” of the blue. In a gas stove, you can easily see the “center” of the flame. In a gas firelpace, you can’t, as it’s hidden by those very logs and whatever stones and such you keep in the fireplace.
Experiment: Remove the logs (wait until they have cooled off!), clean off your grill and such and see if you can spot any blue.
I don’t know the answer, but it seems like a good shot.
Gas burners are designed with mixing valves which take in air, and mix it with the gas before it reaches the combustion location. As it exits into the flame, it is already mixed with enough air to burn completely, and produces a very hot flame. That turns out to be a blue flame, given the temperature of burning methane. If your gas stove, or water heater is not burning blue, it needs cleaning, and it needs it soon. Incomplete combustion in a non vented location is dangerous.
Your gas logs are designed differently, to achieve a different result. The gas is not mixed and is released at the ignition point and instead is allowed to mix with air while it burns. This produces a cooler, and less complete burn, which allows some of the carbon in the methane to remain unburned. That carbon absorbs heat, and then releases it as radiant energy in a characteristic frequency, which is yellow. Since the carbon in wood also releases that same frequency, this is the desired effect of a properly designed fireplace log. Because of the risk of incomplete combustion mentioned above, the fireplace must be vented well.
Just a word of caution: a flame is not a blackbody. Particles of soot (made mostly of carbon) radiate the light that gives the flame its color. The spectrum looks like a continuum, but what you’re really seeing is very closely spaced line emission. The peak wavelength does decrease with temperature (so bluer flames are indeed hotter) but the colors do not correspond to a blackbody curve. E.g. Candles burn yellow, corresponding to a blackbody temperature of 6000K, but really the temperature of the flame is only 700 F.
Thank you, everybody, but especially Tris. (You’re not a fireplace salesman IRL, are you? )
Does this mean that Saint Zero’s fireplace has something wrong with it, if it’s burning blue? All the magazine illustrations of gas logs I’ve ever seen show them burning yellow. Or does he just have a different model? Or do the manufacturers know that consumers want a cozy yellow flame, so that’s how they show it in the ads?
I’m no expert, but I would speculate it’s got something to do with the amount of oxygen the flame can get.
Remember the Bunsen Burner (sp?) back in science class.
Start it with the shutter at the base closed and you get a large yellow flame you can put your hand through… open the shutter and you get a small blue (and very hot) flame.