When it comes to specialty coatings, a lot of attention gets paid to end-use needs, application method, and drying. Mixing, is often treated as a formality or forgotten altogether. For anyone running a coating operation, that is a mistake.
Coating Formulations Are Not Homogeneous When Sitting
Specialty coatings are engineered, formulated products. Active components can differ in density and particle size from the carrier they are suspended in, and over time they may settle. A drum or pail that has been sitting for days, or even hours, is not uniform from top to bottom.
Without thorough mixing before use, you are not applying the product as formulated. The result can be reduced functionality, inconsistent coat weights, or adhesion issues with a root cause that is not immediately obvious.
Never Decant Before Mixing
This is one of the most common and most damaging mistakes in the coating process: pulling material from the top or bottom of a drum or pail before mixing.
If active components have settled toward the bottom, the top of the drum is depleted and vice versa. The decanted material is off-ratio, and the remaining drum is now worse off than before you started. You cannot mix the remainder back to specification because a the material will always be out of spec.
The rule is simple: always mix the entire container before any material is removed.
Agitation During Extended Production Runs
Mixing before the run is essential, but may not be enough on its own. When coating is transferred to a sump or reservoir and applied over a long run, settling can continue. This may cause a gradual drift in coat weight and performance that may not be caught until it shows up in quality checks.
For large-volume sumps, continuous or intermittent recirculation is the most reliable solution. For smaller pan setups, periodic manual agitation throughout the run is a reasonable alternative. Either way, a single mix at the start is not sufficient for extended production.
This Matters Most for Functional Coatings
With standard silicones, the issue may not be immediately visually apparent as it may be with tactile or other functional coatings. The issues may lay dormant until the Quality Control process or when the customer receives the product. The coatings are depending on a consistent concentration throughout its application. Mixing and agitation are part of the technical specification, not just good housekeeping.
Questions about your coating process? Reach out to our technical team at acc-coatings.com!