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[APD] Re: Substrates

This group needs an experienced aquarist with a strong background in non-metallic minerals. Then maybe the conjecture level could be lowered a bit by some facts. :-)

I'm not that person, but maybe I come closer than others. I was an electrical engineer, specializing in lasers and optics, but I grew up in the industrial minerals business, and worked in it for my father on several occasions. [He owned the world's largest producer of general non-metallic industrial minerals, and I worked in the mines, the mills, and the laboratories, as a kid (and half way through college).]

Some of the statements here clearly forced me to recall the processes of baking, calcining, firing, etc. that bear on the production of synthetic or altered substrates. They were the same processes used in industry to incorporate his products like feldspar into the old pre-vinyl records, for example.[For you youngsters, records were audio things played with a needle before we had DVDs. :-)]

The various materials, laterite, Fuller's earth, clays, micas, etc. are all pretty well understood, and should not be a big mystery when used as substrate. A "Dogpile" search will overload you with information.

I'll leave the materials for now, but mention a bit about heat processes.

Baking: Low temperature that mostly drives off moisture to make clays rigid, but they can be pretty fragile and delicate, depending on what is in them. In pottery this is the process for making "greenware" before glazing and high-fire finishing. It's great for making nutrient-filled clay balls that will gradually break down and release stuff into the substrate.

Calcining: Literally it is higher temps used to drive off CO2 from limestone to make lime, as a part of the process of making Portland cement. In common use, it is any hot drying process that may or may not involve some fusion to create a more permanent hard product. It may also drive off water of hydration to alter the chemical and physical properties of a mineral.

Firing: Even hotter, such that fluxing agents in clay melt and fuse the material to a hard, even a glassy state -- ceramic. High fire produces stoneware and porcelain. Low-fire produces terra cotta, like common plant pots or aquatic substrates like APS and Flourite. [I suspect they are fired hotter than normal calcining, but don't really know.}


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