Die-a-toe-What?

We’re prepping for a bottling run here at the winery, and there are a few things we need to do in order to get the wines ready. While our very best wines are lovingly produced in small quantities and without any filtration required, we also make some more everyday wines on a much larger scale, and these we have to filter to ensure their stability once they’re in bottle. One filtering medium often used in winemaking is diatomaceous (die-a-toe-MAY-shus) earth, or DE. Lompoc, where I'm living in California, is a large centre for diatomaceous earth mining.   Also known as kieselguhr, DE is pretty interesting stuff with all sorts of uses. In addition to filtering wine and other food products, it’s also used to filter water in swimming pools and fish tanks. Yum! You’ll find DE in other common household products as well, like cat litter--and dynamite. Is your mouth watering yet? It’s also great for killing cockroaches and bed bugs, and cleans up toxic spills like nobody’s business.  If you’re not already out the door in a mad rush to get some DE-filtered wine for yourself, consider what DE actually is: coffin-shaped fossils of hard-shelled microscopic algae. All the exoskeletons link together to make a complex labyrinth for the wine to pass through with bad stuff getting left behind along the way. It starts out as a very fine powder but has very sharp edges (think ultra finely ground glass) so you have to very careful not to breathe it in in its powder state as it's a major carcinogen.. The sharp edges allow it to cut through the hard shells of bugs, making it an exterminator's best friend.   More Detail (for wine students--and wine geeks!) For DE filtering of wine, we use a plate and frame filter--a series of heavy metal frames interspersed with plates and filter pads that we force the wine through.     Each frame holds a DE "cake" about 2 feet square and and inch and a half thick. How does the cake get into the frame? Well, from our big tank of wine that we're filtering (in this case, 6,000 gallons--that's about 2500 cases) we put about 700 gallons into an open top tank that has a high platform around it so we can access it from the top. We use a big long stainless steel "spoon" to stir the wine from above like a big cake mix. Once we've got the wine rolling, we dump in about 25 pounds of the powdery DE.     We stir and stir, (and my aching back can confirm that that big spoon is heavy!) while pumping it into the filter housing where it clings to the pads and forms layer upon layer of stuff until a cake forms in the frames. Frame before filtering Frame after filtering, with "cake" You have to keep up the stirring because the DE is a lazy beast (well it IS dead, after all) and wants nothing more than to lie on the bottom of the tank. We stir it to keep it in suspension and on its way.   Once we've got our cake in place, in a perfect wine world, the subsequent wine zips right through, leaving all its bad stuff behind, and coming out clear, and we get through 6,000 gallons in one very long day. Hmmm. I haven't actually seen that happen yet. While DE filtering is interesting, it's no day at the beach and not my favourite thing to do at the winery. The setup, before we even start filtering, takes about 2 hours--to get everything in place and sterilize the whole system. We hope (at this point in an optimistic and gung ho kinda way) that once we're going, we'll be able to continue on for at least a couple of hours. Wine turbidity (amount of thick stuff in it), though, plays a huge part, and ultimately, it's always a trial and error kind of situation for each wine. This is why I won't wax poetic about the joys of DE filtering. It can be hell. Set up for 2 hours and then it all breaks down after 45 minutes--too much pressure in the filter housing, not enough powdered DE put in, too much DE, more turbidity than we expected in the wine-- the variables are many. The pump slows to a funereal pace and the output of the wine through the housing is at a trickle. Then we have to break it all apart and set it all up again (which takes another hour and a half, at least!). Soooo frustrating. Whatever happens, we have to be there til it's all done, and that sometimes means 10pm or later.    Once we're done with the set up, between rounds, or at the end of the day, breaking it all apart is a messy business. We scoop out the sodden DE, which is now like soft strawberry ice cream (if it's a red wine) with sand in it. You can still feel the sharpness of the DE, and it can irritate the hands. We load it all into a bin to be dumped in the vineyard. Then we spray everything off, coil up the hoses and drag our weary bones home to our beds for a night of diatomaceous dreams.