Capsules are a great thing. They allow us to take herbal and nutritional remedies in an easy-to-swallow dose. And let's be honest-- some herbs taste really nasty without capsules. But do you know how your herbal capsules are made?
Of course, you can buy empty capsules in any health food store. Most of them are made of gelatin (an animal byproduct), but you can also get vegan capsules made of cellulose. Cellulose is the fiber that forms the walls of most plant cells. Cotton is abut 90% pure cellulose. But most vegan capsules are actually a variant form of cellulose called hydroxy-propyl-methyl-cellulose (HPMC), which is smooth and clear, and is usually derived from pine and/or poplar trees. So Euell Gibbons was right when he used to say, "Ever eat a pine tree? Many parts are edible!"
You can also buy a hand-operated encapsulation machine at many health food stores to help you fill your empty capsules. You pull the capsules apart one at a time, and put the bases in the tray provided. You pour some powder on the tray and use a little plastic spreader to push it into the capsules. There is a tamper that packs the powder into the bases, because the capsule can hold more if the powder is packed tightly. So you fill and tamp a few times, and then you put the caps back on one at at time. These little plastic machines might do 20 or even 50 capsules at a time, and with a little practice, you can fill a few hundred capsules per hour. But I doubt you'd want to try to make your living that way. The tricky part is getting a consistent load, not only from capsule to capsule (which isn't easy), but also from batch to batch, where herbs may have different moisture levels, a finer powder grind, or other differences that need to be taken into account.
Modern commercial encapsulating machines come in two types. "Semiautomatic" machines are similar to the hand-operated machine, except that they orient the capsules, put them in the tray, and remove the caps as a batch. The spreading and tamping operations are a little more consistent too, and a good operator can fill up to 30,000 capsules per hour.
Modern high-speed fully automatic encapsulating machines can fill between 100,000 and 400,000 capsules per hour. The machine takes empty gelatin or cellulose two-piece capsules in bulk, orients them so the caps are all pointing up, holds them upright in a rotating turret, removes the cap section of the capsule, fills the bottom section with powder, tamps the powder down into the capsule, tops it off with more powder, tamps another time or two, and puts the top section back on to form the filled capsule. These operations create a lot of flying dust, so although the turret is surrounded by a dust shield, the machine still has to operate in its own small room, so that the dust can be collected and filtered before it contaminates any other machines or processes. Once the finished capsules are collected, they also need to be vacuumed, brushed, or polished to remove the film of fine dust particles that cling to them, so you don't taste the powder so much when you take them.
Although they are called "automatic" machines, setting up a high-speed encapsulator for a production run is a highly skilled job, and more art than science, because every production run and ingredient blend has different physical characteristics. Smooth flow of powder into the capsules is critical. Some herbal powders are sticky with plant resins, which makes them clump, and stick to the machine parts, making for slow going and frequent interim cleaning. Other blends may flow easily into the capsules, but if the capsule is really full it can still be hard to get the cap reliably sealed. Typically the machine will fill and tamp the powder into the capsule several times before the capsule top is pressed on. A slight dimple or rim around the inside the of the capsule cap and the capsule bottom will actually “click” together to keep the capsule locked closed. But if the machine isn't adjusted exactly right, the capsule will be over- or under-filled, cracked, dimpled, or even completely crushed.
Some of the herbal material is lost in the process of filling the feed hoppers, priming the machine, and running test capsules to get the proper fill weight. Throughout the production run, capsules are periodically sampled, tested, and weighed to ensure that product specifications are still being met. At the end of the run, the encapsulation machine must be completely disassembled and cleaned, a process that can take 3-4 hours or more, and any remaining powder in the feed hoppers or machinery is swept out and discarded. Often as much as 4 Kg (10 lbs) of ingredient blend is lost in the setup and cleaning process-- so it pays to do longer production runs, rather than short ones, as you save both material, and cleaning time. And if you are running two or three full-time production shifts, just one such machine can churn out between 1 and 8 million capsules a day. Better get a big glass of water for all of those!