Terminology: Flash in the Pan

In English, the expression "flash in the pan" generally means something that starts off very strongly in the beginning, but fails to deliver a result. The origin of this term actually has to do with firearms. You see, back in the early days of muzzle-loading firearms, such as matchlocks, wheel-locks, snaplocks and flintlocks, the main charge of gunpowder was filled in the barrel, but a second smaller charge of finely ground gunpowder (called the "priming powder") was placed in a small pan on the outside of the barrel, called the "priming pan" or the "flash pan". A small hole (called the "touch hole") connected the flash pan to the inside of the barrel.

A flintlock mechanism. Click on the image to enlarge. Public domain image.

 A matchlock mechanism. Click on the image to enlarge. Public domain image.
In the above image, B is the flash pan with the touch hole leading to the inside of the barrel.

To discharge the firearm, the user would typically ignite the priming powder in the pan by applying some method of ignition (whether a lit match, or sparks from a flint striking steel, or whatever). The priming powder lights up in a bright flame and the flame travels though the touch hole and ignites the main charge of gunpowder that is in the barrel, which discharges the firearm and sends the bullet towards the target.

Well, this is how the process is supposed to work in theory, but it didn't always happen this way. Sometimes, the priming powder would ignite with a bright flame, but the gun would fail to fire. This could happen for a few reasons:

1. The touch hole was blocked by soot and dirt.
2. The flame from the pan didn't travel through the touch hole to ignite the main charge.
3. The inside of the barrel was wet and the main charge of powder didn't light.
4. The user forgot to put the main gunpowder charge in the barrel or didn't load it properly and only loaded the flash pan.

In such situations, the user would see a bright flame and a lot of smoke coming from the flash pan, but after that, nothing would happen.

In the video above, the person deliberately creates a "flash in the pan" effect with his flintlock musket, by only loading the flash pan, but not loading the main charge of gunpowder. As you can see, there is a very bright flame in the beginning, but after that nothing happens.

So there you have it: a flash in the pan is a very flashy start, but with a disappointing result at the end.