Selecting Silica Matting Agents for Coatings

Define the coating and finish

Record the binder chemistry, waterborne or solventborne system, substrate, dry-film thickness and curing conditions. Specify the target gloss and measurement angle. A grade that performs well in one system may behave differently in another.

Compare particle size and surface treatment

Review the full particle-size distribution and its relationship to film thickness. Coarse particles or agglomerates can affect surface feel and clarity. Surface treatment may change wetting, compatibility and handling; compare treated and untreated grades using their own technical data.

Balance matting with viscosity

Assess gloss reduction alongside viscosity, dispersion quality and storage stability. BET surface area and oil absorption help describe a material but cannot independently predict the result in a complete coating. Use the companion guide on BET and dispersion to structure the comparison.

Matting is a coating-system result

The objective is a controlled optical finish together with an acceptable film. A formulation that reaches the target gloss but feels rough, settles during storage or cannot be applied consistently has not met the complete brief. Therefore the selection decision should be made from a set of results, not a single gloss number.

Keep powder coatings and liquid coatings as separate screening problems. A published example such as Evonik’s SPHERILEX DP-0115 concerns powder-coating processing and melt viscosity. It demonstrates the importance of an application-specific grade; it does not establish a mixing procedure or a dosage for a waterborne coating. [1]

Design two complementary comparisons

Equal-dose comparison. Keep silica addition constant across the shortlisted grades. This reveals differences in initial wetting, viscosity and final gloss under the same formulation conditions. State whether dosage is based on total formulation, binder solids or another agreed basis; a percentage without a basis is ambiguous.

Equal-gloss comparison. Adjust dosage within each grade’s technical guidance to reach the agreed gloss range. Then compare viscosity, clarity, surface feel and storage behaviour. This helps identify the best balance for the intended product rather than simply choosing the strongest gloss reduction at one addition level.

Troubleshooting: change the variable linked to the symptom

Rough or gritty surface: inspect dispersion and the coarse end of the particle distribution before attributing the issue to BET. Check whether the apparent defect is an individual coarse particle, an agglomerate or an application artefact. A grind-gauge observation and a controlled drawdown can help separate these possibilities.

Viscosity increase: compare temperature, rest time and measurement settings first. Review liquid demand, wetting and the dose required for the gloss target. Raising mixing speed without recording the thermal and time history makes the result harder to interpret.

Storage settling: evaluate both sediment formation and ease of redispersion. A visually settled sample and a hard, unrecoverable sediment are not the same outcome. Recheck the complete rheology package rather than assuming that the matting agent alone must solve storage stability.

What to send the Biosilico technical team

A useful request includes the binder system, substrate, target gloss, dry-film thickness, reference silica, dosage basis and available dispersion equipment. Add the current problem and a measurement record if the task is troubleshooting. These details allow the BY-O-COAT discussion to focus on a relevant grade instead of a generic “low-gloss silica” request.