Small pile of capsules filled with brown material

5 Ways to Remove Static Electricity From Capsules

Do you know why your empty capsules are sticking together?

During their operation, fully automatic capsule fillers and semi-automatic capsule fillers tend to attract static buildup, due to something called the triboelectric effect. Capsules become electrically charged because they interact with, and eventually separate from, the machine’s components. Static electricity causes capsules to stick together or even jump, which increases the amount of rejected capsules. And do you know what this results in? Soaring downtime levels along with capsules and powders going to waste, losing you time and money. 

Capsules must make contact with parts of the capsule filling machine; it’s an unavoidable part of the capsule filling process. Fortunately, static can be kept at bay with a few simple methods. The capsule type, lubricant, fill weight, machine operation speed, relative humidity levels, and grounding techniques can all play a part in removing the presence of static electricity. Check out these 5 easy ways on how to remove static buildup so that you can get back to successfully filling your capsules in no time.

1. Lubricate Gelatin Capsules

Did you know you can apply powdered lubricants to gelatin capsules? Lubricating gelatin capsules with material such as magnesium stearate, sodium lauryl sulfate, cornstarch, or carnauba wax improves your capsules’ movement throughout the machine during operation and prevents capsules from sticking together in storage. Lubricating gelatin capsules can also reduce static electricity. This can be due to two things: 

  • the structural differences of the lubricants and capsules
  • the capsules’ surfaces becoming smoother, so that the capsule filling machine components interact less with the capsules

2. Increase the Fill of Capsules and Machine Production Speed

Higher capsule weight and raising the operation speed is another effective approach to help with electrostatic charge. 

Think about it– the combination of the increased capsule fill and speed causes the capsules to have a higher inertia. Denser capsules quickly transporting through the capsule filling machine results in less contact between the machine’s components. The discharge chute, in particular, is an area in which static electricity tends to gather. Similarly to using a powder lubricant as a solution to removing static electricity, the lack of interaction between the capsules and the machine components due to inertia works for reducing static electricity.

Capsules with denser weight quickly move through the capsule machine, which results in capsules having less contact with the machine’s components. Less interaction between the capsules and the machine parts prevents triboelectrification (referred to earlier as the triboelectric effect), therefore stopping static buildup and capsules sticking together.

3. Increase Relative Humidity

An environment with low humidity tends to cause static buildup in capsule filling. Moisture quickens the transfer of electric charge, so increasing the humidity level in the working environment can help prevent capsules from sticking together. A humidifier or climate control system can increase the moisture content in the air of your capsule filling environment. It is important to note that to avoid damaging the capsules and/or causing the machine to rust, always keep relative humidity levels no higher than 55% (but make sure that your product is not sensitive to moisture in the air before doing this).

4. Use Vegetable/HPMC Capsules

One solution to static buildup in capsule filling can be as simple as using vegetable/HPMC capsules rather than gelatin. HPMC (hydroxypropyl methylcellulose) powder has anti-static properties and can dissipate electric charge based on its polymer content, meaning that HPMC capsules are more likely to be anti-static.In studies by Wutscher, et al. and Thielmann, et al., HPMC capsules have shown to have low charging behavior in comparison to gelatin capsules, even without powder lubrication.

5. Make Your Working Environment Anti-Static

A reliable way to prevent static electricity during your capsule production is to take proactive steps in ensuring that the machine, empty capsules, and any accessories that you use are static-proof before you even begin operation. You can take a few approaches to remove static from your working environment:

  • Ground the capsule filling machine - A grounding system connects parts of an electric power system with the earth. Grounding sends built-up static discharge to the earth through a conductor and then into a grounding electrode. Grounding your machine will not only help with static buildup on your empty capsules, but will also protect your property from damage and prevent any risk of injury due to shock. 
  • Spray ionized air on the work space, machine, and capsules - Adopting an in-line air ionizer into your capsule production line can dissipate static charge. How does ionized air remove static buildup? When you spray ionized air into the working environment, positive and negative ions spread across the atmosphere, which are attracted to the ions on the surfaces of the capsules and machine with static charge. As a result, the static electricity becomes neutralized, putting a stop to any more charge buildup on the capsules and machine. 
  • Use anti-static equipment, accessories, and instruments - There are a number of tools you use during the capsule filler’s operation and maintenance– why not make sure that they can aid in stopping your empty capsules from sticking together? Anti-static materials inhibit triboelectric charging, which is what happens when empty capsules and the capsule filling machine’s components make contact. Materials such as vinyl food grade gloves and polypropylene plastic scoops for the capsules and powder will curb static buildup.

Interested in dusting your capsules with magnesium stearate? Get your powdered lubricant here. Or perhaps you want to make the switch from static-attractive gelatin capsules to the more static-repellant HPMC capsules? Get in touch with us today to find your static buildup solutions. There are simple solutions available so that your capsules won’t stick together and be needlessly rejected– no more wasting time and money!


Thielmann F, Nakao T, Usui T, Kokubo T, Diez F, Heng JYY, et al. Electrostatic charging behavior of gelatin and HPMC hard capsules. San Antonio: AAPS Annual Meeting; 2013. 

Wutscher, T, Stankovic-Brandl, M, Zellnitz, S, Kobler, M, Buttini, F, Andrade L, et al. Capsule filling process-induced tribo-charging behaviour of HPMC and gelatin capsules with different external lubricants. Drug Delivery to the Lungs. 2020;30(2).

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