Those photos of a modern diesel locomotive ejecting a sizable flame or "fireball" at the exhaust stack have almost become a cliche of certain rail photo sites.

Now look at the steam version:

www.railpictures.net/viewphoto.php?id=405077

{insert random joke about Greek cuisine/water or oil drilling}

Wow, I've never seen that before. Early in our operation of 1522 we would fire up with scrap 2x4s from a lumber truss company until we had about 30 psi to heat the oil and switch over.
One morning I left Lindenwood yards with a reasonable train just before sunup and worked at 5-10MPH until I got past the signal and then opened up the throttle and it looked like the 4th of July, but it wasn't flames like this. I can still remember the traffic alongside on I-44 and wondering what they thought of all the fireworks.

Judging by that color, I'd have to agree with what the photographer says: not very high-quality coal with a potload of fines, heavy carryover in reducing atmosphere into the front end where it piles up, engineer hits the throttle and column of hot carbon-bearing material swirls up into the atmosphere...

Seems to me he's backing up (note the valve gear); see the wisps of dirty smoke from the track where "something" fell down and is smoldering, and see the direction of the safety-valve plume ... then tell me where that enormous cloud of smoke to the left of the picture came from, probably the initial eruption. Enough time has elapsed to have nice hot combustion gas running through to be entrained and heat things up...

I thought that only happened in back to the future! I guess next rivets are going to start shooting out from around the boiler courses...

Nope. That's a former British War Department 2-10-0, built by North British Loco Co. The British WD 2-10-0's, as with most of the British steam of that era, had cylinder cock ejection tubes that pointed straight up the middle of the track, instead of to the sides as we are accustomed to here in the States. That's cylinder cock exhaust you see, not gray smoke.

.

I would guess that the unburnt fuel doesn't have enough oxygen in the tubes; when the material reaches the stack, it's got enough heat to ignite when it reaches the open atmosphere. We've had the same thing happen with oil fuel on the New Hope Valley.

I have also seen oil burners do this, but only on very rare occasions. The fire goes out in the firebox, the smoke comes out the stack, the conditions are just right, and (the tricky bit) there's some source of ignition. Not sure if it's bit of flame sucked through the tubes or where the ignition comes from. Doesn't seem like there's a lot of potential ignition sources, which may explain why I've only seen it happen a few times.

you may have thrown a quick fresh bed of coal on then hit the throttle, air rush thru the tubes and unburnt fuel out the stack igniting.

While some of the Narrow gauge steamers had spark arrestors, many used wood, this is fairly common in Steam traction engines using wood when they work hard with snappy stack talk sparks are flailing out the stack.

I have one question..

When did GE start building steam?

Sorry, could not resist..

Great to see this image of S/L Catawissa, whose owner, in addition to his enviable ability to blow smoke rings at will, is also a highly skilled whistle artist!

.

thats a little more arty time lapse at night enhancing the effect.

You get a similar effect with bagasse-fired steam locomotives:



Bagasse is crushed and dried sugar cane after they've squeezed the juice out of it. It's used for fuel in many places where sugar cane is grown.