Extending the
open time of paints

Driven by the wish to reduce VOC/SVOC in paints, the shift from solvent-based to water-based formulations has made it difficult for formulators to control the period during which irregularities in freshly applied paint can be repaired. With special additives for extending the open time of water-based acrylic and PU paints, as well as cutting-edge testing methods, we help paint makers solve this challenge.

Working with paints that dry too quickly can be frustrating for consumers and professionals alike. The time during which freshly applied coatings remain wet enough to correct brush and lap marks is commonly referred to as open time. It is closely related to workability, i.e. how easily paint can be spread, brushed and layered. Wet edge time, during which overlapping paint layers do not leave visible lap marks, is generally considered part of open time.

Our high-performing dispersing and wetting agents can be used as open time extenders that push the time window for correcting paint films wide open – improving workability, wet edge time, as well as other crucial properties such as gloss, leveling and sagging. What’s more, our experts have developed state-of-the-art methods for assessing how well our additives improve open time, and which best meet your specific needs.

Paints are complex systems due to the large number of additives they contain. After application of the paint onto the wall, dynamics between binder and other ingredients occur that influence the open time and drying time. Our experts have studied the influence of additives on these phenomena of additives using a combination of advance measurements and standard tests including:

• Self-developed 12-pin geometry to measure paint torque and viscosity change over time
• Rheolaser measurement of Brownian motion to monitor surface dynamics changes
• Cross tests and overlapping tests to validate the performance of selected additives that extend the open time of paints

The result is a broad portfolio of accurately tested open time extenders for acrylic and PU lacquers that reliably boost workability and ease of use.

These short videos show how we use a Rheometer with a specialized geometry and Rheolaser setup to measure open time. They also show two methods to approximately assess open time in the lab, using cross and overlapping tests.