By now most people who spend time in the out of doors have at least heard of, if not used, ferro rods of one type or another. They first popped up back in the mid 80's when the magnesium emergency fire starters that were issued to pilots first started showing up in military surplus stores. Then later on came the Strike Force fire starter in the late 80s, which has a tinder compartment built in and comes with wetfire tinder cubes, and the Boy Scouts of America Hot Sparks fire starters which were smaller and more easily portable. In time the LMF fire steels were very popular among bushcrafters and students of wilderness survival. To this day the Strikeforce is still preferred by many of my friends up north due to the size and ease of use with gloves on.
All of the types of ferrocerium rods I've listed initially, the first ones to hit the global survival market (and later the bushcraft market), are of the harder type of ferrocerium rods. Any abrasion on these types of rods begets sparks. Light pressure yields lights sparks, and harder pressure yields hotter sparks, but essentially any scraping of the surface at all produces the pyrophoric result. That would change just after the turn of the century. A new and different style of ferrocerium rods, ones labeled as “mischmetal”, would come along and create havoc for some people. It would be the topic of many discussions on outdoor forums back in 2006, and it even caused more than a few arguments about which was better.
The truth is that ferrocerium is mischmetal and mischmetal is ferrocerium. They are in fact one and the same. The only real difference is that the softer type has a lower iron content, but the difference between the two made it necessary to have a way to differentiate them. So Mischmetal was the name settled on for labeling the softer rods. Iron is the element that makes this rare earth composition hard enough to produce the sparks when abraded, and adjusting the percentage of iron adjusts the the hardness of the composition in the rods. The harder the composition the easier to spark it is and the longer it will last, but the smaller the sparks. This works fine in disposable butane lighters where the fuel is very easily ignited. The softer type takes more speed and pressure to strike, but produces bigger hotter sparks that burn longer, because the striker cuts away more of the material as it ignites. Both have their pros and cons. The harder type doesn't wear as fast, so even with the cooler sparks it could serve longer in a dry climate. The softer type does wear quicker, but the bigger hotter sparks could serve you better in a high humidity climate. Another way the softer mischmetal rods have an advantage in a wet environment is because the rods themselves can be whittled into tinder.
By using a good sharp knife to make slow deliberate and controlled movements of the blade, and making no sudden movements, shavings can be cut from the mischmetal rods. Essentially In the same fashion as shavings are scraped from a magnesium fire starter, just more slowly. I find I have the best results by doing this with light-pressured thumb pushes on the spine of the blade with the off hand, to apply the pressure directly in line with the cut being made. This is the same cutting method I use when cleaning up notches in trap trigger components. With this method the hand holding the knife handle is only there to hold the knife in alignment as it rotates during the cut. The off hand actually does the work in this case. This allows for much more control of the blade's movement than applying the pressure from the handle. This is very important to keep from moving the blade too suddenly and quickly, and igniting the shavings prematurely.
So, just because it has been an unusually wet trip, and you've already used up the petroleum soaked cotton you had crammed into the capsule of your ferro rod handle, doesn't necessarily mean that you are out of options for an accelerant to start the fire with. If you are carrying one of the softer mischmetal rods, then you still have another choice to try. It will just be more work than using prefabbed tinder material. In this picture, the material on the left is half of the petroleum soaked cotton that was in the handle of the ferro rod in the picture. it has just been fluffed up to create more surface area. The material on the right is a pile of mischmetal shavings collected in part of an acorn shell. The mischmetal shavings will not burn as long as the other material will, but it burns quite a bit hotter. This shot was taken a few seconds after ignition, after the really intense flames of the burning metal had started to settle down some. Under those lighting conditions, the camera couldn't focus on the initial white hot flare.
In this shot, taken form more of a distance at a lighter time of day, you can clearly see the amount of energy produced in the initial flare immediately following ignition, and just how dynamic the reaction actually is. The burning mischmetal creates a very intense reaction, it burns at over 5000 degrees Fahrenheit. It should be noted that this isn't where I would have placed the tinder if the goal had been to actually ignite this fire. In that case I would have had the tinder under the bark with all of the heat rising through the bark. In this case I was merely wanting to capture an image that would illustrate the reaction, but it still ignited the damp cedar bark even from the side like this. The burning ferrocerium produces a fair amount of heat.
The Pro Tip for using a magnesium fire starter is to use some sort of vessel to collect the shavings in, because the shavings are so light and susceptible to being scattered by even a slight breeze.. An acorn cap or nut shell can work really well for this in a woodland environment, and in urban environments bottle caps can serve the same purpose.
In the task of whittling mischmetal shavings to use for tinder, the Pro Tip is to use two collection vessels. The idea being to whittle a few shavings into one collection container, transfer those to the other container, then go back to whittling shavings into the original container again, repeated the process as needed, The point being to avoid igniting the shavings prematurely.
So yes, for some people one of the down sides of the softer mischmetal rods is that they are softer so they wear faster. Sometimes they throw shavings, long thin curly ones even, rather than sparking so they wear even faster still, and because of the shavings they can even be a bit frustrating at times. Yet it may be helpful to know that even so, it is a characteristic that can be exploited and put to a positive use in a pinch.