When a customer says that capsules have become brittle, crack easily, or break more often during filling, the first reaction is usually the same: is there something wrong with this batch of capsule shells?
Sometimes there is a shell-related issue. But in many projects, the answer is not that simple. An empty capsule is not used in isolation. Once it meets the fill material, the final behavior can be affected by moisture, packaging, storage, transport, opening time, and the filling process.
Before jumping to conclusions, it is better to clarify four things: when the brittleness was first noticed, what kind of material was filled, how the capsules were stored after opening, and whether the issue appeared before filling, during filling, after locking, or after transport. For pharmaceutical empty capsule projects, these details also affect size confirmation, sample testing, quality documents, batch traceability, and future bulk supply communication.
1. Start With the Stage Where the Problem Appears
The same phrase, “the capsule is brittle,” can point to very different causes.
If breakage is found before the bag is opened, the first checks are usually transport, cartons, inner bags, batch number, and retained samples. If brittleness appears after the bag has been open for some time, the storage environment and resealing method matter more. If breakage rises during filling, equipment speed, capsule separation, locking pressure, powder dust, and polishing may all need to be reviewed.
| When it happens | What to check first | Useful information to collect |
|---|---|---|
| Breakage before opening the original package | Transport, carton condition, batch, packaging unit | Arrival photos, carton/bag number, batch number, retained samples |
| Brittleness after the bag is opened | Exposure time, low humidity, resealing method | Opening time, room temperature and humidity, storage method for remaining capsules |
| Breakage during separation or filling | Machine settings, capsule moisture, fill material behavior | Machine model, speed, station where breakage occurs, rejection reason |
| Breakage after locking or polishing | Overfill, locking force, mechanical friction | Target fill weight, locking condition, polishing setup |
| Breakage after packaging or transport | Finished product packaging, hygroscopic fill, vibration | Packaging format, transport conditions, customer-side feedback |
Once the stage is clear, the investigation becomes much more practical. You know whether to look first at the empty capsule shell, the fill material, the packaging, the equipment, or the customer’s handling environment.
2. Moisture Is Not Simply “The Lower, the Better”
Moisture is central to capsule shell brittleness, but it should not be treated as a race to the lowest possible number.
For gelatin empty capsules, moisture is closely related to shell flexibility. If the shell loses too much water, it may become more brittle. If it absorbs too much moisture, it may soften, deform, or stick.
HPMC empty capsules have a different moisture profile and are often considered for some low-moisture or moisture-sensitive formulations. Even so, switching to HPMC does not automatically solve every stability issue. The fill material, packaging, storage condition, and finished product stability still need to be checked together.
In real projects, the point is not one isolated “capsule moisture” value. It is the moisture balance inside the whole system:
the capsule shell has its own moisture state;
the fill material may absorb moisture, release moisture, cake, or discolor;
air and headspace inside the package may participate in moisture exchange;
desiccants can change the internal humidity;
outside temperature, humidity, and repeated opening can continue to affect the product.
Looking at only one part of this system can lead to a misleading answer.
3. The Fill Material Can Change the Capsule Shell
Many teams first look at the capsule shell. That is reasonable, but the fill material may also change the way the shell behaves.
Herbal powders, plant extracts, mineral powders, probiotics, dietary fibers, and sugar- or salt-containing ingredients can have different levels of hygroscopicity. If the fill material keeps drawing moisture from the shell or from the package environment, the capsule may gradually lose flexibility and become more likely to crack.
The opposite can also happen. If the fill brings in too much moisture, or if the package environment is too humid, the capsule shell may soften, stick, deform, or separate poorly during filling.
That is why a hygroscopic formulation should not be discussed only in terms of capsule size. Size matters, but it is not the whole story.
During sample testing, it is useful to observe three states together: the fill material, the capsule shell, and the package. Check the appearance immediately after filling, then watch for cracking, caking, softening, odor change, residue, or locking issues after storage.
For moisture-sensitive projects, it may be worth evaluatingHPMC empty capsules for low-moisture formulations, packaging barrier, desiccant strategy, and stability observation. For routine powders and established products,gelatin empty capsules for conventional powder fills remain a mature option.
The material should be selected according to the project, not treated as a universal answer.
When StellarCaps discusses pharmaceutical, nutraceutical, dietary supplement, or OEM/ODM projects, the first questions are usually about the fill material, target fill weight, gelatin or HPMC capsule choice, packaging format, and sample testing.
4. Packaging and Opening Practices Are Often Underestimated
A capsule shell may leave the factory in a suitable condition, but that does not mean it will remain unchanged under every customer-side condition.
Packaging is part of stability. Bottles, blisters, aluminum pouches, desiccants, seals, outer cartons, storage, and transport can all affect the moisture balance between the shell and the fill material.
Some issues do not happen inside the unopened original package. They happen after opening.
For example, empty capsules left open in a low-humidity room before filling may gradually lose moisture. Finished bottles that are opened and closed repeatedly may experience changing internal humidity. A desiccant, if not evaluated properly, may protect the fill material while pulling too much moisture from the capsule shell.
At minimum, these questions should be clear:
How long are empty capsules exposed after the bag is opened?
Is room temperature and humidity recorded?
How are remaining empty capsules resealed and stored?
Is the finished product packed in bottles, blisters, or pouches?
Is a desiccant used, and has its amount and placement been evaluated?
How long will the consumer use the product after opening?
These sound like storage and packaging details, but they may affect cracking, softening, fill weight, appearance, and product stability.
If a project is moving from sampling to bulk purchasing, the supplier’s supply rhythm, quality documents, and batch traceability should also be confirmed early. Otherwise, the sample may look fine, but the team may still have to go back and fill gaps when bulk production, stability review, or customer complaints begin.
5. Photos Help, but They Are Not the Whole Investigation
Photos are useful when a customer reports brittle capsule shells. They show where the breakage occurs, what the surface looks like, and roughly how large the issue is. But photos only show what is visible. They do not explain why it happened.
What really helps is a shared set of facts that quality, R&D, production, and the supplier can discuss together.
| Information to collect | Why it matters |
|---|---|
| Batch number, capsule size, color, and packaging condition | Shows whether the issue is linked to one batch or packaging unit |
| Fill material and physical state | Helps assess moisture absorption, caking, volatility, or shell interaction |
| Opening time and room temperature/humidity | Helps identify exposure to overly dry or humid environments |
| Stage of occurrence and breakage ratio | Separates incoming material, filling, packaging, transport, and end-user feedback |
| Machine model and problem station | Helps check separation, filling, locking, and polishing factors |
| Retained samples and comparison samples | Shows whether the customer-side sample differs from unopened retained samples |
Not all information will be available at once. Still, the more complete the picture, the closer the team gets to the real cause. A useful review is not about assigning blame; it is about reducing repeated trial-and-error in the next sampling, filling, and production run.
If the problem is concentrated around the filling process, it may help to reviewempty capsule filling performance and production-line OEE. If the fill material includes probiotics, plant extracts, or other moisture-sensitive ingredients, the article onprobiotic capsule shells, HPMC capsules, and active stability may also be relevant.
How StellarCaps Supports This Type of Project
For customers, capsule brittleness is rarely just an after-sales issue. It can involve formulation, packaging, filling trials, quality documents, and supplier communication.
Jilin Xingyuan Capsule Co., Ltd. (StellarCaps) is located in Huinan Economic Development Zone, Tonghua, Jilin Province, China. The company serves pharmaceutical, dietary supplement, nutraceutical, and OEM/ODM customers as an empty capsule manufacturer. StellarCaps focuses ongelatin empty capsules andHPMC empty capsules, with a factory area of about 60,000 square meters and an annual capacity of up to 20 billion capsules. Common sizes such as 00#, 0#, 1#, 2#, 3#, and 4# are available, with support for color, printing, sample testing, quality documents, batch traceability, and bulk supply communication.
For a brittle-capsule project, the useful starting point is clear project information: fill material, target fill weight, packaging format, quality review requirements, expected purchase volume, and timeline. The clearer the information, the easier it is to align00#, 0#, 1# and other capsule size options, sample testing, packaging moisture control,empty capsule quality documents and batch traceability, and future supply planning.
If the fill material is hygroscopic, odor-sensitive, color-sensitive, or has packaging stability requirements, it is better to raise these points during inquiry and sampling. That makes it easier to decide whether to test gelatin empty capsules, HPMC empty capsules, or packaging adjustments first.
Frequently Asked Questions
Why do capsule shells become brittle?
Common causes include capsule moisture loss, hygroscopic fill materials, long exposure after opening, low room humidity, insufficient packaging protection, and excessive mechanical stress during filling or locking. The cause should be checked together with the stage where the issue appears.
What should I do if empty capsules become brittle after opening?
Check how long the bag has been open, the room temperature and humidity, and whether the remaining capsules were resealed properly. If brittleness appears only after long exposure in a dry room, opening and storage management should be reviewed first.
If capsules crack a few days after filling, is it a capsule shell quality issue?
Not necessarily. If cracking appears only after filling, the fill material, packaging, desiccant, storage condition, and transport vibration should be reviewed together. Retained empty capsules and filled samples should be compared.
Why do herbal powders or plant extracts sometimes increase cracking risk?
Some herbal powders, plant extracts, and dietary fibers are hygroscopic. They may change the moisture balance between the capsule shell and the package environment, which can increase brittleness or cracking over time.
Can switching to HPMC empty capsules solve capsule brittleness?
HPMC empty capsules may be considered for some low-moisture or moisture-sensitive projects, but they are not a universal fix. The fill material, target fill weight, packaging format, and stability observation still need to be evaluated together.
How can I contact a manufacturer for samples and quotation?
Prepare the fill material information, target fill weight, capsule size, packaging format, expected purchase volume, and photos of the issue. Then contact StellarCaps for sample and quotation discussion. Clearer project information helps determine whether to test gelatin empty capsules, HPMC empty capsules, or packaging adjustments first.