The particle size distribution curve is an essential tool for visualizing the particle size distribution in a solid or liquid sample. It allows for the precise interpretation of a product's characteristics based on its particle size distribution, a crucial criterion for the performance, stability, and conformity of industrial formulations. Whether in the food, cosmetics, pharmaceutical, or materials industries, reading and analyzing this curve enables process optimization and ensures product quality. This article explains how to interpret a particle size distribution curve, what information to glean from it, and why conducting particle size analysis in the laboratory is essential for controlling your processes.
Table of Contents
A visual representation of particle distribution
The particle size distribution curve is a graph that represents the distribution of particle sizes present in a sample. It allows visualization, cumulatively or differentially, of the proportion of particles belonging to different particle size classes, as a function of their equivalent diameter.
The horizontal axis (x-axis) represents the size classes, generally expressed in micrometers (µm) or nanometers (nm). The vertical axis (y-axis) indicates the corresponding fraction of particles, either as a percentage by mass, volume, or number. The logarithmic scale is frequently used on the size axis because it facilitates the representation of very wide ranges, particularly when a sample contains both fine and coarse particles.
This representation is essential for analyzing the particle size distribution of a powder or liquid containing solid particles. It allows for the characterization of a wide variety of materials: flours, cosmetic powders, mineral additives, pigments, plastics, or colloidal suspensions.
A key concept for the performance of industrial products
The particle size distribution curve is not merely a descriptive tool. It is central to many functional properties of products. Indeed, particle size directly influences:
- Chemical reactivity (in catalysts or medicines, for example)
- Solubility and dissolution rate (particularly in pharmaceuticals and nutraceuticals)
- Texture (in cosmetic creams or food products)
- The stability of suspensions (in chemistry or in the environment)
- Mechanical or thermal behavior (in composite materials or metal powders)
A product with homogeneous particle size (narrow distribution) will behave very differently from a product with a wide distribution, where fine and coarse particles coexist. The particle size distribution curve therefore allows for the precise adjustment of industrial processes, such as grinding, sieving, dispersion, or granulation, to achieve the desired performance.
Statistical indicators to quantify the distribution
To effectively interpret a particle size distribution curve, several statistical indicators are used. They allow the distribution to be summarized in a few key values:
- D10 : 10% of the particles are smaller than this value. This indicates the proportion of fines.
- D50 : also called the median, this is the size at which 50% of the particles are smaller, and 50% are larger. It represents the "average" size of the sample.
- D90 : 90% of the particles are below this value. It gives an idea of the largest particles present.
These three points allow us to assess the extent and homogeneity of the distribution. The smaller the difference between D10 and D90, the more homogeneous the particle size distribution. Other indicators, such as the mean diameter (MD) or the polydispersity index (PDI), can be used for more in-depth analyses, particularly in the case of nanoparticles.
What is the purpose of particle size analysis?
An essential quality control tool
Particle size analysis is frequently integrated into quality control protocols. It allows verification of the conformity of raw materials and finished products to defined specifications.
For example, a cosmetic powder manufacturer must guarantee a smooth and homogeneous texture. Inconsistent particle size distribution could result in a grainy feel or poor application. In the pharmaceutical industry, variations in particle size can affect the bioavailability of an active ingredient by altering its rate of dissolution in the body.
The particle size distribution curve is therefore used to detect process deviations, to control consistency from one batch to another, and to identify anomalies that may impact the quality or safety of the product.
A lever for optimizing industrial processes
Beyond control, particle size analysis plays a fundamental role in optimizing manufacturing processes. It allows for the adjustment of critical steps such as grinding, dispersion, granulation, or drying.
For example, in the food industry, particle size influences the consistency and stability of a syrup or sauce. A powder that is too fine can cause clumping or lumping, while a powder that is too coarse may not disperse well in the liquid.
In additive manufacturing or powder metallurgy processes, particle size determines the melting rate, the density of the final part, and the consistency of the layer-by-layer deposition. Controlling the particle size distribution curve therefore directly impacts the mechanical performance and reliability of the product.
To guarantee this control, it is recommended to regularly carry out a particle size analysis D10, D50, D90 , in order to monitor the evolution of the size distribution throughout production.
A regulatory requirement in certain sectors
In many regulated industries, particle size analysis is required by authorities. Health authorities, food safety agencies, and environmental bodies impose precise particle size criteria to guarantee product safety and traceability.
In the field of dietary supplements or nutraceutical products, excessively large particle size can affect intestinal absorption. Conversely, the presence of undeclared nanoparticles can pose regulatory compliance issues or create perception problems among consumers.
Particle size analysis is also used in environmental risk assessments, for example, to monitor the dispersion of particles in air, sediments, or wastewater. In these cases, laboratories must use validated measurement methods and provide full traceability of results.
Concrete examples of use by sector
In the food industry , particle size analysis allows for control over flour milling, the solubility of milk powders, and the distribution of grains in baked goods. It plays a key role in the formulation of protein supplements and fortified beverages.
In cosmetics , it ensures the fineness of makeup powders, the smoothness of creams, and the stability of emulsions. Even distribution enhances the product's sensory appeal and reduces visual imperfections.
In the environment , it is used to analyze fine particles (PM10, PM2.5) in the air, the particle size of sediments in rivers or the dispersion of industrial sludge.
In the pharmaceutical industry, it plays a role from the initial formulation development stage to adapt the dosage form (tablet, capsule, suspension) to the optimal particle size. It determines the release kinetics and the reproducibility of the treatment.
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How is a particle size distribution curve read?
A two-axis semi-logarithmic representation
The particle size distribution curve can be represented in two main forms: the frequency curve (differential distribution) and the cumulative curve (cumulative distribution). The latter is the one most commonly used in laboratories and industrial testing.
The horizontal axis represents particle size, generally expressed in micrometers (µm), sometimes in nanometers (nm), and often displayed on a logarithmic scale . This choice is justified by the wide range of sizes analyzed, which can vary from a few nanometers to several millimeters. The logarithmic scale allows for clearer and more precise readings, particularly when dealing with nanopowders or heterogeneous mixtures.
relative frequency (as a mass or volume percentage) or the cumulative distribution is represented . In the cumulative version, the curve rises gradually from 0 to 100%, reflecting the proportion of particles smaller than a certain size.
A point on the curve indicates that a certain percentage of particles are less than (or equal to) a given size. This visual reading allows for a quick identification of the major characteristics of a sample.
Interpret the key values: D10, D50, D90
Reading the curve is based mainly on three characteristic values: D10, D50 and D90 .
- D10 corresponds to the size below which 10% of the particles are smaller. It is an indicator of the finest particles in the sample.
- D50 , also called the median, indicates that 50% of the particles are smaller than the median size, and 50% are larger. It is a widely used reference value for describing the overall particle size distribution of a product.
- D90 corresponds to the threshold beyond which only 10% of the particles remain. It reflects the proportion of coarse particles in the sample.
These three points define the distribution range of the sample. The smaller the difference between D10 and D90, the more homogeneous the distribution. Conversely, a large difference indicates a wide distribution, with particles of highly varied sizes.
For example, a powder with a D10 of 3 µm, a D50 of 15 µm, and a D90 of 40 µm has a relatively wide distribution, but one still compatible with many industrial uses. If the D90 were 100 µm, the formulation would be potentially unstable or not conforming to specifications.
To better understand the impact of the particle size distribution curve in formulations, see our article dedicated to the interpretation of particle size distribution curves .
Evaluate the homogeneity and quality of a sample
Beyond the cut-off points D10, D50 and D90, the analysis of the shape of the curve provides important qualitative information.
steep and narrow curve means that the particles are very close in size: this is a monodisperse , often sought after in high-precision technical applications (pharmaceutical formulations, powders for 3D printing, etc.).
wider curve indicates a polydisperse , meaning one containing particles of varying sizes. This can be intentional (for specific mechanical or sensory properties), but it can also be a sign of a poorly controlled manufacturing process.
The polydispersity index (PDI) can complement this analysis. It is a statistical parameter derived primarily from dynamic light scattering (DLS) measurements. The closer the PDI is to 0, the more homogeneous the particle population. Conversely, a high PDI indicates significant size dispersion.
What are the analytical methods for obtaining a particle size distribution curve?
Sieving: a simple and robust method
Sieving is the oldest and most accessible method for evaluating the particle size distribution of a solid sample. It relies on the use of calibrated sieves, stacked in decreasing columns, through which the sample is separated by size.
The sample is placed in the upper sieve and then subjected to mechanical agitation (vibration or rotation). Each particle passes through or is retained depending on its diameter, which then allows the mass retained on each sieve to be weighed and the corresponding particle size distribution curve to be plotted.
This method is suitable for dry materials with sizes greater than 40-50 µm. It is widely used in the fields of construction, mineral processing, flour, plastic or food granules.
However, it has limitations for fine powders, cohesive particles or wet samples, which require other, more precise techniques.
Laser diffraction: the modern reference method
Laser diffraction particle size analysis is currently the most widely used method for measuring size distributions ranging from a few nanometers to several millimeters.
It is based on an optical principle: when a laser beam passes through a suspension of particles, the light is diffracted at an angle that depends on the diameter of the particles. Sensors record the intensity of the scattered light at different angles, and algorithms reconstruct the particle size distribution from this data.
This method allows for rapid, reproducible measurements applicable to dry or liquid samples. It is governed by the ISO 13320 , which outlines the test conditions, validation criteria, and interpretation of results.
Laser diffraction is widely used in the pharmaceutical, cosmetic, chemical, food processing and materials industries.
Dynamic light scattering (DLS): for nanoparticles
Dynamic Light Scattering (DLS) is a method dedicated to the measurement of very small particles, generally less than 1 µm.
It relies on the analysis of Brownian motion of particles suspended in a liquid. Laser light is scattered by the moving particles, and the recorded intensity fluctuations allow the calculation of the average size and polydispersity.
This method is particularly suited to colloidal formulations, emulsions, liposomes, nanopowders, or biological suspensions. It provides parameters such as the mean diameter (MD) and the PDI (polydispersity index) .
DLS is widely used in biotechnology, materials chemistry, and health products.
Sedimentation and centrifugation: for suspended particles
These methods are based on Stokes' law , which describes the sedimentation rate of a particle in a fluid as a function of its size, density, and the viscosity of the liquid.
The time required for each fraction to reach a certain position (in a centrifuge tank or tube) is measured. This data is then converted into particle sizes.
Sedimentation is well suited to suspensions of intermediate size (between 0.5 and 100 µm), such as muds, clays or certain pharmaceutical preparations.
Centrifugation accelerates the process and improves accuracy, but requires specialized equipment and more complex protocols; it can be performed efficiently through laboratory analysis of sedimentation dynamics
Image analysis: a direct and morphological approach
Image analysis relies on the direct observation of particles under an optical or electron microscope. Specialized software identifies each particle, measures its size and shape, and extracts a particle size distribution.
This method is particularly useful for irregularly shaped powders, or when visual appearance (roughness, elongation, regularity) is as important as size. It also allows particle size analysis to be combined with chemical identification techniques, such as scanning electron microscopy coupled with EDX.
Image analysis is used in quality control, research, or failure studies.
All of these methods can be combined to provide a complete particle size characterization, adapting to the nature and complexity of the samples.
The accuracy of the measurement also depends on the sampling and preparation conditions, as shown in the following section.
The accuracy of a particle size analysis depends as much on the method used as on the rigor of the sampling and sample preparation conditions. In the laboratory, each protocol is designed to guarantee the representativeness, traceability, and reliability of the results. This fifth section highlights the technical requirements governing these analyses, drawing on the standards applied in accredited laboratories.
Analytical conditions and laboratory protocols
Samples packaged in suitable containers
The quality of analytical results depends largely on the quality of the sample. For particle size analyses, particularly by laser diffraction or DLS, the particles must be properly dispersed, not agglomerated, and representative of the batch being analyzed.
Laboratories require packaging in airtight and inert containers to prevent external contamination, liquid phase evaporation, or interaction with the container. Plastic or borosilicate glass materials are preferred, depending on their chemical compatibility with the analyzed product.
Customers are given precise instructions on the quantity to send, the precautions for picking and the delivery time.
A controlled and reproducible analytical method
Once the sample is received, the laboratory applies a internal protocol , in accordance with the recommendations of international standards, such as ISO 13320 for laser diffraction.
The choice of method depends on the expected particle size, the matrix (solid or liquid), and the objectives of the analysis. The laboratory may opt for a dry (dispersion by air) or a liquid method (dispersion in a compatible solvent), depending on the behavior of the particles.
The measurement is carried out in several passes, with controlled agitation, background measurement, and regular recalibration of the device to ensure data reliability.
Limit of quantification and measurement range
The **limit of quantification (LOQ)** depends on the method used and the type of equipment. For laser diffraction, it generally varies from 0.1 µm to 10 µm , while DLS allows down to 1 nm .
Laboratory instruments such as the Malvern Mastersizer 3000 offer a wide measurement range from 10 nm to 3 mm , allowing for the analysis of both nanoparticles and coarse powders.
The results are provided in the form of raw data tables and cumulative or differential curves, with D10, D50, D90, DM, and PDI values where applicable.
Complete traceability and metrological rigor
COFRAC ISO 17025 accredited laboratory , every step of the analysis is tracked: from sample receipt to report transmission. Worksheets, calibration certificates, and internal quality controls support the process.
What information can be derived from a particle size distribution curve?
Defining the quality of a product based on its particle size
Particle size distribution is a direct indicator of the quality of a powdered or suspended product. An excessively wide particle size distribution can lead to instability, visual defects, or altered texture. Conversely, a narrow and well-controlled distribution ensures consistent performance.
For example, in a powdered dietary supplement, an excessive proportion of fine particles can lead to poor dissolution, clumping, or a loss of bioavailability. In a cosmetic cream, poorly controlled particle size can result in an unpleasant feel or even irritation.
A regular curve, centered on a D50 that meets expectations, with closely spaced D10 and D90 values, is often a sign of a stable, well-formulated product that is reproducible from batch to batch. It is also a guarantee of control over the manufacturing process.
Adapting formulations and industrial processes
Particle size data is invaluable for optimizing formulations or readjusting production parameters . A simple variation in size distribution can alter a product's behavior at different stages: mixing, grinding, transport, dosing, application.
For example, in the food industry, a powder that is too fine can generate dust or stick to equipment walls, while a powder that is too coarse can settle too quickly in a beverage. In the field of polymers, the distribution of mineral fillers can influence mechanical strength or dispersion within the matrix.
Thanks to the particle size distribution curve, manufacturers can:
- Correcting a formula by changing the proportions of raw materials
- Adjust the grinding or sieving parameters
- Reduce material waste or cleaning time
- Improve the consistency of product performance
By integrating particle size data into a validation plan or a quality control loop, companies secure their productions and increase the robustness of their processes.
To further analyze texture or flow properties, a complementary rheological analysis may prove essential.
Why use a laboratory for particle size analysis?
Ensuring compliance with standards and regulations
An accredited laboratory has calibrated equipment, validated methods, and traceability that complies with international standards, such as ISO 17025 or ISO 13320. This allows manufacturers to guarantee the reliability of results, especially when they need to be communicated within a regulatory or contractual framework.
In certain sectors, such as pharmaceuticals, cosmetics, or food processing, particle size analysis is required in registration dossiers or quality audits. A recognized laboratory report then provides essential added value.
In addition, the laboratories apply strict protocols regarding sample preservation, internal quality control and certificate issuance, thus ensuring full compliance with customer and authority requirements.
Benefit from comprehensive technical expertise
Beyond simple measurement, a laboratory offers a true scientific interpretation of the results . Its experts can advise on the most suitable method (sieving, laser, DLS, etc.), recommend dispersion protocols, or analyze anomalies in the curves.
They can also carry out comparative studies on several samples, develop tailor-made methods for complex matrices, or integrate particle size analysis into a multi-parameter study (rheology, specific surface area, porosity, etc.).
This level of expertise allows manufacturers to save time, secure their decisions and rely on robust data to improve their processes or validate their products.
Outsourcing to gain agility and responsiveness
Outsourcing particle size analysis also means choosing flexibility and speed . Specialized laboratories are able to process samples within short timeframes, adapt their measurement ranges to each need, and deliver usable results in the form of standardized or customized reports.
This allows companies to focus their internal resources on innovation, while relying on a trusted partner for critical analyses. Whether in the development phase, routine production, or in the event of a quality dispute, this approach guarantees maximum responsiveness and consistent reliability .
YesWeLab support for your particle size analyses
YesWeLab collaborates with a network of over 200 laboratories across France and Europe, all selected for their technical expertise, analytical capabilities, and accreditations. Particle size analyses are performed according to standardized protocols, including ISO 13320 for laser diffraction and ISO 17025 for COFRAC-accredited laboratories .
Depending on the client's specific needs, YesWeLab directs requests to the most appropriate laboratory: sieving analysis, dry or liquid chromatography, DLS for nanoparticles, or imaging for complex materials. This approach guarantees reliable, documented results that can be used for regulatory, industrial, or R&D purposes.
A digital platform to centralize and track your requests
One of YesWeLab's major strengths lies in its all-in-one digital platform , designed to facilitate the management of analytical services. From this interface, users can:
- Search and select a method from over 10,000 available analyses
- a quote or service in just a few clicks.
- status of their samples in real time , from submission to results availability.
- Download the analysis reports and archive the results in a secure space
This digitalization allows for increased speed, traceability and reliability , while reducing processing times and the risk of administrative errors.
Diverse and complementary application sectors
The particle size analyses offered by YesWeLab cater to a wide variety of industrial sectors. Each sector has specific requirements that necessitate adaptation of protocols and methods.
- Food processing : control of flour fineness, milk powder solubility, suspension stability
- Cosmetics : homogeneity of makeup powders, texture of creams, size of exfoliating particles
- Nutraceuticals and animal health : bioavailability of supplements, formulation of powders and granules
- Polymers and materials : characterization of mineral fillers, powder for additive manufacturing, homogeneity of mixtures
- Environment : monitoring of particles in water, air or soil, analysis of sludge and sediments
YesWeLab also supports design offices, ingredient manufacturers, formulators and quality departments in their occasional or recurring needs.
A tailored approach, from formulation to compliance
Each analytical project entrusted to YesWeLab receives personalized support . An expert contact person is assigned to monitor the case, advise on the choice of method, validate the conformity of the protocol and ensure the correct interpretation of the results.
YesWeLab does more than simply provide a D50 value or a basic histogram. The goal is to help manufacturers make the most of their data , detect discrepancies, anticipate non-conformities, or validate an innovation.
Whether it is a routine test, a product development or a regulatory requirement, YesWeLab positions itself as a technical and strategic partner serving quality, compliance and industrial performance.
