The humble apple. With over 7,500 different varieties worldwide, this simple fruit seems to have its place in nearly every culture. And with each region comes special breeds that have been adapted over time for the express purposes of that culture and region. One of the clearest areas of distinction is along the lines of cider versus eating apples.
Most folks don't realize at first that there is such a thing. If it's good enough to eat, why wouldn't it be good enough for cider? And vice-versa, right? It all comes down to acids and tannin, which at different levels determine the perceived sweetness of the apple. Ideally, a good balance comes down to exactly 0.4% acid and 0.2% tannin. Eating apples don't usually have the right level of tannin in them. And even within the subset of cider apples it is rare to find any one particular type that is outstanding for use in cider.
Over time it has been found that the best ciders are crafted from a blend of apples. Through testing the acid and tannin levels, the right balance and blend can be determined scientifically. But most home brewers don't have access to this type of technology and have to rely on experimentation and the built up collective knowledge within the craft. Fortunately for all of us that knowledge base is quite extensive.
So what type of apples do you use? Convention holds that you should use one from each category (acid, tannic, sweet) but in practice that may not always be the case. Baldwins, Cortland, an McIntosh are a decent blend - with the Baldwin adding subtle sweetness to the acidity of the McIntosh and the tannins of the Cortland. But those are also widely considered eating apples. By contrast, Kingston Black, a heritage variety, was bred more for cider and is pretty close to the specs for "perfect" cider - Blend it with Sweet Coppin to offset the bittersharp characteristics (over goal on acid/tannin) of the Kingston Black.
As with any alcohol, the maker's preferences are going to play a role and shine through. Perhaps you like your cider a bit sweeter, or enjoy a nice pucker from extra acidity: No combination is right or wrong so long as you enjoy it!
Have a favorite blend for making cider? Share it in the comments!