The Importance of Open Time in Ceramic Adhesives
The construction coatings industry has evolved significantly in recent decades, shifting from traditional systems based solely on cement, sand, and water to highly engineered formulations that meet increasingly specific technical requirements. This change has not been merely aesthetic or functional, but structural: today, a coating’s performance no longer depends solely on its base components, but on the precise control of its behavior during application and throughout its service life.
In this context, the incorporation of additives has marked a turning point. Advances in construction chemistry have made it possible to modify key properties of the cementitious system, such as water retention, workability, adhesion, and drying times. This has led to ceramic adhesives that are more consistent, predictable, and better suited to real-world construction conditions, where factors such as temperature, substrate absorption, and tile formats play a decisive role.
The incorporation of redispersible polymers, cellulose ethers, and rheological modifiers made it possible to precisely control critical system variables, transforming cementitious adhesives into formulations designed for specific performance. Among these properties, open time stands out as a key parameter in the interaction between the material, the substrate, and the application conditions.
Open time: the critical factor in ceramic adhesives
The open time of ceramic adhesives refers to the period during which the material retains its ability to wet the substrate and develop effective adhesion. It is a critical parameter, as it depends on water retention, polymer film formation, and the progression of hydration.
When this open time is insufficient, a surface film forms that limits proper interaction between the adhesive and the coating, reducing effective contact and bond strength. A well-designed open time allows for variations on-site and ensures consistent system performance.
Factors that affect on-site time
• Ambient temperature
• Wind / drafts
• Substrate absorbency
• Coating type and absorbency
• Application thickness
How can you tell if your adhesive meets the open time requirement?
According to the NMX-C-420-ONNCCE standard, open time is measured by assessing how long the adhesive retains its adhesive strength after application.
The procedure is as follows:
• The adhesive is spread over a standard surface using a notched trowel.
• It is left to cure for a specified period of time.
• Next, a tile is placed on the surface while applying pressure.
• Finally, the bond strength is measured (usually by tensile testing).
The NMX-C-420-1-ONNCCE-2017 standard does not specify a single open time value, but rather defines it based on the adhesive’s classification.
The minimum values are:
• Type A: ≥ 10 minutes
• Type B: ≥ 12 minutes
• Type C: ≥ 15 minutes
• Type D: ≥ 20 minutes
The Importance of Ensuring Your Adhesives Comply with the Standard
Compliance with the standard is not merely a technical requirement; it is a guarantee of performance under real-world conditions. An adhesive that meets established parameters—such as open time and bond strength—offers greater reliability on the job site, reduces the risk of failure, and strengthens the manufacturer’s reputation with its customers.
In an increasingly competitive market, regulatory compliance has become a key differentiator. It is not just a matter of formulating products to pass a test, but of developing products that are consistent, stable, and capable of withstanding variations in process and environmental conditions.
This is where technical support makes all the difference. At Treechem, we provide specialized support in formulation, as well as a laboratory for performance evaluation and validation, which allows us to fine-tune systems precisely and ensure that every development meets the required criteria. This not only reduces development times but also minimizes risks when introducing new products to the market.
Beyond compliance, it’s about building reliable, reproducible solutions that align with today’s industry demands.
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