Pipe Mud and Pipe Cement (WARNING: GIANT POST)

So you probably know what pipe mud is. If you don't it's pipe ash mixed with water (or saliva) to form a paste. This paste is used in a pipe chamber to fill defects and change the chamber geometry (usually in the bottom). This can be used to fill a sandpit on the inside of a chamber, raise the bottom of a bowl to the level of the airway, or plug the sides of the shank in a corncob chamber. This paste dries in a day or so and over the course of many smokes the pipe mud will absorb tars, oils, and moisture and will harden to become an indistinguishable part of the surface of your chamber. Pipe mud is a great tool and is pretty much like duct tape when it comes to doing anything in your chamber. Now, most people use pipe ash for this but you could just as easily use cigar ash or cigarette ash. They all pretty much act the same. They stick together when wet and form a workable paste. What I've found to work the best is actually wood ash such as from your fireplace. This performs the same function as pipe mud but, as I've found, more effectively. Although it is similar to tobacco ash it is also quite different. I actually call it pipe cement and I'll tell you why.
A major component of wood ash is calcium carbonate. This is what makes this ash a good fertilizer, especially for plants which need a lot of calcium. Calcium carbonate is also known as limestone and happens to be the major component of... *drumroll*... portland cement. In manufacturing the limestone is crushed into a powder and heat treated at high temperatures to become chemically active. Your fireplace burns hotter and more completely (in a chemical sense) than your pipe. This creates ash which not only contains more calcium carbonate but which is also much finer and which contains calcium carbonate which has been heat treated at a higher temperature. This makes your fireplace ash chemically different than your pipe ash. To put it shortly: your fireplace ash is a cement, your pipe ash is not. Take a look at this picture:

Left is pipe ash, right is fireplace ash. Notice that the fireplace ash is much whiter and has a fine grain size. Notice that the pipe ash is black and clumpy.
So you're thinking: so what? Who cares if fireplace ash is a cement, pipe ash has worked to make pipe mud for generations why should I switch now? Well, you're right there is no reason to switch and pipe ash works perfectly fine as pipe mud. I'm just an engineering student that works in a cement lab so I find this interesting. And also, as I'm about to tell you, pipe cement has some up sides where pipe mud falls short.
First of all, pipe cement has much more agreeable working properties. That is to say it handles nicer as a paste. Since pipe cement is a fine powder you can slowly mix water into it with your pipe spoon until it becomes the consistency of play-dough. Pipe mud on the other hand tends to be a crumbly mess like dirt or... well... like mud. Take a look at the following photo:

Notice how the cement has been made into an even mass while the pipe mud is an uneven and crumbly. At this point you can simply put the ball of cement on the end of your poker tool and lower it into your chamber, then you can press it and form it into the perfect contours in your chamber. Pipe mud does not handle half as nice as pipe cement
Next there is the drying time. Pipe mud dries, meaning the moisture from it needs to evaporate before you can smoke your pipe. This takes 24 hours or so. After that the pipe mud is delicate until it has been smoked enough to absorb tars and oils and become hardened like cake. Since pipe cement is a cement it cures rather than drying. By this I mean that it reacts chemically with the water and the H2O molecules become part of the cement. This takes about 4 hours and you have a smokable pipe. After 24 hours you have a fully cured cement which makes a satisfying "clink clink" sound when you tap it with your tool.
Your pipe cement will also cure to be much harder than the pipe mud. Take a look at the following photo: I pressed with the same amount of force with my spoon (3 hours after initial mixing) and you can see the difference in strength.

So now you're thinking: so what? This is a pipe not a bridge why should I care how strong my pipe mud is? And you're right it's not that important but if you drop your pipe and your lump of pipe mud falls out that would not be great.
There is also the matter of porosity. Pipe cement is amazingly porous! I estimate it can absorb at least its own weight in water. And dries fast. It is definitley superior to pipe mud in these terms. It's actually so great at picking up moisture and oils and tars that I've even thought about lining a briar pipe's chamber completely in pipe cement (kind of like meerschaum lined briar pipes).
So there you have it... there's my little blurb about pipe mud and pipe cement. I don't claim I "invented" this or anything. I'm sure this has been thought of before but I have not found it in my search on this forum so I thought I should write this down here. If anyone does this I'd love to hear your personal experience with it. And if there is a reason people don't do this I'd love to hear it too! Although, from my personal experience I have not found any negative side effects of pipe cement.

Thanks! I'll be selling Pipe Cement for 29.99/lb starting next week.
Just kidding :D

It's true most people use cigar ash. And it is better than pipe ash because its finer which makes for better workability but it is still closer to pipe ash than it is to wood ash.

To tell you the truth the left image is actually a mix of cigarette and pipe ash from some black cavendish which left a lot of dottle (cause I couldn't smoke it all the way because I thought it was awful stuff) it was used simply for picture purposes. I usually use something that does look more like cigar ash, either from cigarettes or from pipe ash that was well burnt, and I sift out the dottle. I'm not a big cigar smoker so I don't often get a hold of cigar ash but I have done this with cigar ash. And, as I said, it is usually finer which gives it better workability (as in you'll be able to make it more play-dough and work it better) but it does not have the same drying/curing results. From what I've seen, no tobacco ash forms what I would call a cement. As in I have seen no sign of a chemical reaction. So you wet it, work it, and dry it. It does not cure fast and it does not cure to be as hard as the wood ash. The wood ash cures to be literally a rock.
Anyways, having said all that this is not as scientific as it sounds. I do have some expertise in the field but I do not claim to know it all. I actually work mostly with chemical cements which do not resemble portland cement at all and which have no calcium content. There are general rules for cements but even then... these things have a tendency to become really complicated the longer you look at them. At the same time every tobacco is different. If there's something I've learned from working in a cement lab is that details do matter. A change from ph7 to ph8 in your solution might mean the differnce between a cement that cures to a rock and one that doest react at all. Your experience with pipe mud will depend what you smoke as the different tobaccos and additives as well as how you smoke can have a butterfly effect on what you end up with. I can see how some cigars and tobaccos might actually give you something that closely resembles the wood ash and some other ones (especially heavily aromatic ones) might give you pure crap. In fact what kind of wood ash you have might even make a difference! Mine seems great but yours might be crap. So yeah... things get complicated fast haha.
I think I'll get a hold of a cigar and try the 3 (cigar, wood, and pipe) ashes side by side. I think I opened pandora's pipe mud box.

Good evening everyone,
So I went out and bought a little captain black cheap cigar and made a pipe mud ball out of its ash (left). I also did the same with wood ash pipe cement (right).

So as you can see there is a bit of a difference in scale haha. That's cause you can't get a lot of ash out of those little cigars. But that doesn't actually affect the experiment.
So ... if both of these pipe mud balls were simply wet particles that dried by evaporating water (rather than curing by chemical reaction) you would expect the small cigar ash ball to dry and harden significantly faster than the big pipe cement ball. In fact, the exact opposite happened. The big ball hardened much faster. As well, it became much harder than the cigar ash ball which simply crushed back to powder with little pressure. This is what gives me the impression that the wood ash cures and pipe ash simply dries.
But the cigar ash was finer than pipe ash so its workability in the paste was quite similar to wood ash.