Laser diffraction troubleshooting usually starts when results already disagree across sites. At that point, teams compare D10, D50, and D90 without matching dispersion energy. However, laser diffraction reports an equivalent size that depends on dispersion state. So, “the same powder” can deliver different PSDs when the method energy shifts. Most disputes come down to three controllable variables. First, dispersion pressure changes how far agglomerates break up during measurement. Second, obscuration affects stability, noise, and multiple scattering risk. Third, reports often omit settings, so nobody can replicate the method precisely.

Use this workflow for dry dispersion laser diffraction, especially for cohesive powders.

Choose one stable control sample from your normal product family. Define success as stable Dv50 and Dv90 with low repeat variability.

Start at the lowest pressure that still gives stable feeding and acceptable obscuration. Increase pressure in small steps, for example, 0.5 bar per step. At each step, record Dv50, Dv90, obscuration, and the feed setting used.

Plot Dv50 and Dv90 versus pressure and look for a clear plateau region. A plateau means added pressure no longer changes size in a meaningful way. Select a setpoint inside that plateau and define a narrow allowable range.

A plant received a complaint about a rising Dv90 after a lot change. They ran a pressure titration and saw Dv90 fall until 2.5 bar, then stabilize. Next, they standardized 2.8 bar with a 2.6 to 3.0 bar method window. They also locked obscuration limits and repeat rules for every run. As a result, both sites matched within tolerance and closed the complaint fast.

A titration curve tells you what the dispersion energy actually does.

This pattern typically indicates that agglomerates disperse to a stable endpoint. In that case, the plateau pressure becomes your standard method setting.

This pattern often suggests attrition risk or fragile structures breaking under energy. Lower pressure, validate with microscopy, or use a gentle wet reference method.

This can indicate multiple binding regimes, including moisture bridges and solid bridges. Therefore, control conditioning time, humidity exposure, and storage history carefully.

• Teams chase D10 shifts while ignoring curve shape and feed stability signals.

• Operators run at high obscuration because the screen looks “steady.”

• Labs change pressure between runs, then compare data as if methods match.

• People skip background checks, then blame powder when noise inflates the tail.

• Reports omit disperser configuration, so other sites cannot reproduce the setup.

copy this checklist into every PSD report you share externally.

• Disperser model and configuration, including nozzle and venturi selection

• Pressure setpoint and allowed range, chosen from the plateau region

• Feed rate target and an acceptable obscuration window

• Measurement time, number of repeats, and background policy

• Pass criteria, including max variability for Dv50 and Dv90

Use wet dispersion as a reference when attrition risk complicates dry settings. Record dispersant, mixing time, sonication time, and power level for traceability.

• Re-run the sample using your pressure titration series and log all settings.

• Keep obscuration inside the defined window across repeats.

• Compare the curve shape, not only the D-values at one pressure.

• Check the conditioning history, including humidity, storage time, and packaging conditions.

• Share the one-page method sheet with every external PSD report.