Why are hardeners in 2K finishes specific to the sheen of the product?
Damian Bush, technical director at Berger-Seidle America, answers:
This is a common question. Contractors sometimes wonder if things could be simplified by using one hardener for all sheens offered in a 2K finish. Some even speculate if they can mix, for example, a half gallon of ultra-matte and a half gallon of semi-gloss to achieve a satin result. Those who have chosen to listen to manufacturer representatives and other industry instructors would tell you simply: Do not mix different products, and only use the hardener specified for the sheen in use. It’s the safest approach—and the topic warrants a proper explanation.
First, it’s important to understand there are multiple types of isocyanates available to chemists when formulating a water-based floor finish. Hydrophilic isocyanates are used in water-based coatings because they are compatible with the hydroxy groups of the chosen resins. The concentration of these within the formulation is one factor in play. Additionally, some hydrophilic isocyanates are more highly compatible than others. The highly compatible ones usually end up influencing the sheen to a higher gloss level while those less compatible lead to a lower gloss. A finish could theoretically be formulated to use the same hardener for all gloss levels, but more matting agents would be required for low-sheen options to compensate. In the end, each manufacturer will weigh the factors when choosing how to formulate their coatings.
A wood flooring professional is wise to follow the instructions for mixing their 2K finish, ensuring the sheen labeled on the hardener canister matches the one listed on “part A.” While many coatings are similar and follow basic rules of chemistry, the ingredients have been chosen very carefully. By deviating from manufacturer’s instructions, you are taking risks. Each product is the end result of much development and fine-tuning to create a product with a specific purpose in mind. Purchase the product that features the characteristics you prefer and the results you seek. Happy finishing!
