The experiment: see the effect racking has on natural fermentation. Cider will ferment itself, a lot easier and with less worry than most people imagine. (I've spoken with cider-makers who fret about acid levels and the dangers of wild microorganisms. Acid is a natural defense against infection, and many cider makers, even the ones who pitch their yeast, feel that cider above a pH of 3.6 or 3.8--the number varies--will go wrong. I discovered that cider makers in Europe, including those in France and England who regularly have cider above those levels, don't worry about infections at all. And Kevin doesn't, either.) If you let it sit in the carboy in cold conditions--I kept mine below 55 degrees--natural yeast will ferment all the sugar out of the juice. All you really have to do is keep it cold.
Now, interestingly, if you want to keep the juice from fermenting all the way out, you can actually retard fermentation by starving the yeast. One method is keeving, which is a convoluted method of removing nutrients from the juice before fermentation. The other method is racking, or transferring the juice. When you do this, you manage to leave a lot of yeast behind (it slowly settles into a cake as it ferments). In the new carboy, the left over cells, those that are still active, try to rouse themselves to eat all that tasty fructose floating around. They bud and divide and create a new population. This both removes oxygen from the juice (a generally good thing) and also some of the nutrients. This is key because eventually the yeast eats all the nutrients that keep it going. They'd probably love to keep eating, but they run out gas. This is how the French are able to have very sweet ciders that are stable in the bottle.
It turns out you don't have to rack very often to get the effect. The idea was to rack one of them enough to get the yeast to crap out, and let the other one run to dry. Left to my own devices (and a brain full of misinformation based on beer fermentations), I would have started racking early and often--probably every two weeks until it stopped barely after it had started. No!, Kevin said. Rack no more often than once a month and tell me what you find. So I did. Here were the first two months' findings. (If memory serves, the juice started out around 1.044, but I stupidly forgot to note it down.)
Carboy 1: 1.030 (racked)
Carboy 2: 1.030 (racked)
Carboy 1: 1.018 (not racked)
Carboy 2: 1.020 (racked)
After checking the March gravity, I decided to rack Carboy 2, the laggard, once more. It was already going slow, so I figured I'd slow it down even more and let the other one run. That's all it took. After that, carboy 2 didn't need to be racked again and just naturally slowed down. Here's how they proceeded.
In case it's not legible, the twice racked carboy tested at 1.016 in April and 1.012 when I bottled yesterday. The once-racked carboy dropped to 1.012 in April and 1.002 today. Both seemed to still be fermenting very slowly when I bottled. That's good, because I hope the 1.012 stuff will naturally carbonate. I was worried that the other one wouldn't have enough sugar left to carbonate, so I added about half a tablespoon. (I'm also worried that that was a mistake, but once I was mid-bottling, there was no time to speak to Kevin. We'll find out whether it was a bad move or not. But either way, it will be educational!)
Both ciders are sweet and fresh, with not a hint of anything wrong. The tannins are still pretty rough, but smoother than they were in April. I expect they'll continue to soften as the magic of biochemistry continues. So there you go: the simple effect of racking on juice. I expect the cider to be spectacular, but of course, it's the orchardist who gets all the credit. All I did was store his carboys.