Just purchased some Optisorb the other day and it's exactly the same as the NAPA stuff*. It can be crushed with your fingers if you really try, and if you roll it between your fingers underwater it will erode quickly. But in a pot, it has lasted me 1.5 years without losing any structural integrity. Ive found it does compact over time when used straight, which may reduce the air pockets between each particle, but using it in a mix seems to negate this.
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I've read Optisorb it's not calcinated while 8822 is. But I've seen just as many people claim 8822 turns to muck, and I've not experienced this personally. So I investigated the issue and I'm determined to prove once and for all that they are the same.
Exhibit A: EP minerals oil absorbent product line
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NAPA 8822 is the "floor-dry" brand, which as you notice is specifically noted to be kiln-fired while the other DE products are not. This means the other DE products must not be calcinated, right? Im not so sure. It smells like a marketing technique to sell an "extra safe" tier of product, but is actually the same.
Exhibit B: EP Minerals product spec sheets for each brand:
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Their descriptions are identical, both "kiln dried". They come from the same plant. They are the same in nearly every way except that Optisorb has a slightly larger particle size on average and appears to be marketed to a French, possibly French-Canadian market.