Gelatin capsule

How Empty Hard Gelatin Capsules Are Formed

At Shaoxing Zhongya Capsule Co., Ltd., every batch begins the same way most hard gelatin shells are produced worldwide: stainless steel pins are dipped into a temperature-controlled gelatin solution, withdrawn, rotated, and dried in stages before the cap and body are trimmed to length and joined. This pin-dipping process is the reason an Empty gelatin capsule shell has such a consistent wall thickness — uneven dipping speed or drying airflow is one of the more common causes of brittle or oval-shaped shells further down the line.

The typical shell-forming sequence

1. Pins are dipped into the gelatin bath at a controlled temperature and viscosity
2. Pins rotate slowly while the gelatin film sets evenly around the mold
3. Shells pass through a multi-zone drying tunnel with gradually reduced humidity
4. Cap and body sections are stripped from the pins, trimmed to exact length, and joined
5. Finished shells are sorted and inspected for wall defects, spots, and length variance

Because a Gelatin capsule shell made of gelatin is essentially a dried protein film, drying speed matters more than most buyers expect: dried too fast, the shell becomes brittle; dried too slow, cap and body can stick or deform during the joining stage.

Matching Capsule Size to Fill Volume

Size selection is one of the first practical decisions in any capsule filling project. An Empty hard gelatin capsule that is too large for its fill weight leaves powder able to shift and settle inside the shell, which can affect fill weight consistency on high-speed lines; a size that is too small forces overpacking and can slow down capsule closing. Our production line at Shaoxing Zhongya currently covers eight capsule sizes — 00#, 0#, 1#, 2#, 3#, 4#, 00B#, and 0#EL — which lets formulators match shell volume to fill density instead of reformulating around a limited size range.

Transparency, Opacity and Formulation Visibility

Whether a formulation calls for a Transparent Empty Capsule or an opaque shell usually comes down to two competing needs: light protection for sensitive actives, and visual inspection of the fill during production and by the end user. Transparent shells let quality inspectors see fill uniformity, color, and the presence of foreign particles without opening a capsule, which is useful during in-process checks on a filling line. Opaque or pigmented shells, on the other hand, are often chosen to mask fill color variation between batches or to reduce light exposure for photosensitive ingredients. A Pharmaceutical hard gelatin empty capsule can be produced in either finish from the same base gelatin formulation, so the choice is a formulation decision rather than a manufacturing limitation.

In practice, many formulators request a small trial batch in both finishes before committing to a production run, since the same fill can look and behave slightly differently once it is visible through a clear wall versus hidden inside an opaque one.

Moisture Content and Shell Stability

Gelatin shells are hygroscopic, meaning they gain or lose moisture depending on the humidity of the room where they are stored and filled. Too little moisture and the shell becomes brittle, prone to cracking during transport or on a high-speed capsule filler; too much moisture and shells can soften, stick together, or deform under their own weight in storage. Most hard gelatin shells are kept within a target moisture band during production and packaging to balance flexibility against structural strength.

Controlling this range at scale is largely a matter of drying-room consistency and warehouse conditions, which is where facility scale starts to matter. Producing an Empty Gelatin Capsule at high volume without moisture drift requires stable drying tunnels and climate-controlled storage rather than a single well-tuned production line. Shaoxing Zhongya Capsule Co., Ltd. operates a 40-acre facility that includes a 20,000-square-meter modern production plant, staffed by a team of over 70 skilled employees, which supports an annual production capacity of 8 billion capsules — scale that helps keep drying and storage conditions consistent from one batch to the next rather than only during small trial runs.

Frequently Asked Questions

What is the difference between an empty capsule and a filled capsule?

An empty capsule is just the two-piece gelatin shell, supplied unfilled to manufacturers who then dose it with their own powder, granule, or pellet formulation on their filling equipment.

Can the same capsule size be used for different powder densities?

Yes, but the fill weight will change. A dense powder fills a given shell size at a higher milligram weight than a light, fluffy powder of the same volume, which is why fill weight ranges are given as a span rather than a single number.

Why do some capsules feel harder or more brittle than others?

This is almost always related to moisture content at the time of testing. A shell tested in a very dry room will feel more brittle than the same shell tested in a more humid one, even though nothing about the shell formulation has changed.

Is 00B# the same as 00#?

No. 00B# is a slightly shorter body variant used when a formulator wants the fill volume closer to 00# but with reduced overall capsule length, often to suit specific filling or packaging equipment.

Do transparent and opaque capsules perform differently once filled?

Mechanically they are comparable when made from the same base formulation; the main practical difference is visibility of the fill and light exposure, not shell strength or disintegration behavior.