LECA - short for "Lightweight Expanded Clay Aggregate" - is a generic term that refers to any number of such materials produced all over the world, intended originally for use in making lightweight concrete. (The weight of concrete precludes its use in buildings beyond a certain height. If you make it lighter, you can build taller.) Hydroponic growers in Europe noted that it might make a good growing substrate, so it began to be remarketed for that purpose.
PrimeAgra is a registered trademark for a particular brand of LECA, selected specifically because it was made for horticulture, rather than remarketed to it, and therefore has properties that make it better for the application.
Over time, the particle size control of the original PrimeAgra seemed to wane, so I contacted the manufacturer with the intent of fixing that (size uniformity being an important parameter). As it was going to require some equipment upgrades anyway, which would extend the lead-time to get the new batches, the question arose if there was anything else that might be done to improve its performance, and that's what led to this "new and improved" version.
Basically, they keys to success are uniformly-sized and approaching spherical particles to maximize the free air space between them, a smooth surface to enhance the capillarity, very fine pores at the surface to quickly absorb water that might "bridge" the macropores without leaving large surface pockets that could do just that, and small, uniform internal porosity that absorbs and releases moisture quickly and steadily.
So by manipulating the clay/binder system and the firing profile, the manufacturer was able to enhance all of the above. Interestingly, and something I had not anticipated, the new material is actually heavier than the old stuff, which keeps it in the pot better and the plants seem to "lock in" faster.
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