If your follow up question is, "Are you meaning to say, in an unfortunate dad-humor sort of way that you are hot in a Hugh Jackman sense, or do you mean that you, as a highly exothermic chemical reaction going about his day, are generally uncomfortably warm?" To this I must admit it's a bit of both, but mostly the latter, and here's a thing: both my bod and blacksmithing would, from a sort of...sad...4th grader grasp on chemistry, seem to be exothermic - that is, producing heat as a byproduct of reaction - but while smithing, I am also absorbing a great deal of the forge's heat, which would make me some sort of exo-endo-therm chimera, which seems impossible to my barest of understandings of chemistry, but there it is.
Which is a great example of the kind of fast-and-loose approach to understanding chemistry that I promise to employ throughout this entire project. And so you, dear reader, find me today; struggling mightily to stretch my mind around a subject wildly beyond my ken: Geopolymers. What are geopolymers? For two days now I've been wrestling with this, and here's my best answer: Geopolymers are a mixture of organic or inorganic compounds. An answer as unsatisfying as it is vague and useless, mostly because it seems that a huge variety of materials and compounds fall under this umbrella, and they can be made from all sorts of stuff (which, etymologically, makes sense since the word itself is basically Greek for "a bunch of rocks or whatever"). But let me chop it down to what geopolymer is gonna mean for the practical purpose of my project. Henceforth, I'll call "GP" anything that acts like concrete (aka, liquid stone), but is made up of highly silicate (and possibly aluminate) material.
Why is this important to my project? Moreover, what is my project? Right, I'm building a forge. I could take the easy way out and buy some firestone bricks, or forego the insulation altogether and go with a simple brake-drum style open forge, but I've been there and done that, and I think it would be really fun and useful to know how to make GP, not just for refractory purposes, but as a building material in general (given its emerging popularity as a low-cost, industrial byproduct-eating, earth-friendly alternative to concrete). "But, Ben," I hear you saying, "firebricks are like...$9 each and I can tell already that this is going to be a stupidly deep rabbit hole of a project." Yes. Yes, you're right. However, based on how my previous four jobs have valued my time, $9 is practically a week's worth of 9-5 work, which means I can chase this rabbit pretty far before I'm losing money on time investment.
Here is some light reading on GP's. These are a few of the sources I've been reading through trying to get the gist of it all, sans misc youtube and wiki's, some of which I'll toss in as I go:
The distilled version of this is, I think, "Pick a glassy mineral, dissolve it in an alkali, add it to some clay or some such, cure it with fire (or not, maybe), voila, GP."
My current understanding is there are two/three components, but I could be wrong here - the mixing phase is still a little mysterious to me at this point.
- An Alkali of at least pH 10, e.g.
- Lye (Sodium Hydroxide [NaOH])
- Lime (Calcuim Oxide [CaO])
- Hydrated Lime Calcium Hydroxide [Ca(OH)2])
- Natron (which, seems to be functionally near enough to washing soda, aka Sodium Carbonate [Na2CO3]
Now that we have a list of ingredients, let me butcher for you the chemical processes that form a GP. To roughly translate from here a bit, I would describe it thusly:
- Initial Mixing - An alkaline solution is used to dissolve Si and Al ions from the amorphous phases of the feedstock. I take this to mean that anything non-crystalline in structure (aka, your silicate ingredient) gets dissolved by the alkali.
- Condensation - In the resulting solution, the Si and Al hydroxide molecules condense with adjacent hydroxyl ions, forming oxygen bonds (and water). I think that at this stage you have a monomer solution of silica and aluminum in water, just waiting to polymerize.
- Poly-condensation (aka Polymerization) - an application of heat (apparently anywhere from ambient temperature to no more than 90ºC) causes the monomers and any leftover Si and Al hydroxide to polymerize into rigid chains/nets of oxygen bonded tetrahedra. I believe this is a science-y way of saying, "Then you dry it out and it gets hard."
Now here's where my ignorance of both chemistry and cement mixing really begin shine. I'm left with the following questions:
- Is waterglass essentially a solution of "monomer-ized" Si/Al hydroxide waiting to be catalyzed into GP? I'm guessing that waterglass has no Al in it, and that for this purpose you would ideally want as pure a solution of dissolved SiO2 as you could get before adding it to an amorphous aluminosilicate strata for to make it into bricks and whatnot. I really have a very bad grasp on what I'm talking about here...
- In terms of choosing a silicate material to dissolve in your alkali, the best example I've seen is in that youtube clip, where he used silica gel and added it to perlite, and perlite is essentially corn-puffed obsidian by composition at least. Well I live in Bend, OR and there are literally big-ol' heaps o' obsidian lying about. Could I dissolve obsidian in an alkali to make waterglass, or would the magnesium and iron in it mess it up? It would be awesome to have obsidian waterglass.
- I have learned that Portland cement is basically a calcium silicate, Al/Fe blend that sets when mixed with water by way of "a complex series of chemical reactions still only partly understood." I can remember partaking of cement mixing in the past and I feel like I remember it involving mixing the cement powder with equal parts sand and gravel/stone, and then adding water to a desirable consistency. With GP's it seems waterglass is kind of an equivalent Portland cement, which you would then add to whatever you want bound. I wonder how far off base this understanding of the process is?
- Given that GP's are practically entirely glass and aluminum, I'd assume they are by default pretty damn fireproof, but I don't trust my grasp of the situation enough to rule out that there may need to be modifications/additions to the recipe to make this material useful for me as a forge liner. If so, I wonder what they are?
So there it is. I've got a long way to go, but I feel like I'm on the right track. All this geopolymer nonsense aside though, I don't have a really satisfactory big-picture plan for how this operation will come together. Since I'm renting a duplex in a pretty cramped little cul-de-sac, I have neither an indoor nor an outdoor work space that I can call my own. I've been drawing up some crude plans for a blacksmithing trailer, and have been keeping an eye on the trailer market on Craigslist for a few weeks now, but so far nothing is leaping out at me. M'lady, Bucket, and I have been eyeballing the house market too, which is the long-game, low-fun solution to this problem, but I'm ready to smith NOW. I'm keen on the trailer idea owing to both my nomadic tendencies as well as a desire to make it possible to bring smithing to the community in the form of Blacksmithing Camp. Since Bucket is big-lady-on-campus with a camp organization here in Bend, she's designing all sorts of programs for all times of year, and I feel like I'd be a shoe-in for some of those. So yeah, Blacksmithing Trailer (aka OPERATION "ROLLING THUNDER") is a subject for another time.
Thanks for your interest! If you know anything about this stuff or, through reading have discovered that I've totally got it all backwards and upside-down, please, PLEASE let me know in the comments or jot me an email or something. You guys are the best.
Big Love, Ben