Understanding the drying time of the paint is critical to the coating process. The drying process of coatings from liquid to solid is usually divided into three stages: surface drying, actual drying and complete drying.
Division of drying stages
The drying process of coatings is an important transition process of coatings from liquid to solid state, which is generally divided into three main stages: surface drying, actual drying, and complete drying.
1. The surface is dry
Surface drying is the initial stage in the paint drying process. At this stage, the surface of the paint appears to be dry, but not yet fully cured.
Exterior features:The surface of the paint does not look wet and shiny, it does not feel sticky to the touch, and it can already be touched lightly without leaving a mark.
Test Method:Commonly used test methods include blown cotton balls, finger touch and small glass balls. Among them, the cotton ball blowing method is achieved by placing a degreased cotton ball on the surface of the coating film and blowing the cotton ball with the mouth, if the cotton ball can be blown away without leaving fibers, it is considered that the surface is dry.
2. Actual drying
Actual drying is the second stage in the paint drying process, also known as mid-drying. At this stage, the surface of the coating is dry and resistant to slight pressure or deformation, but is not yet fully cured.
Exterior features:The surface of the paint already has a certain hardness, and it can be determined by a simple test method whether it is actually dry.
Test Method:Commonly used methods include filter paper pressing, cotton ball pressing, blade method, thick layer drying method, and non-marking test method. For example, the filter paper pressing method uses a drying Tester weighing 200 grams, presses the dry filter paper or degreased cotton ball on the coating film, and after a certain period of time, the Tester is removed, and if the filter paper can fall freely without leaving traces or the coating film does not lose its luster, it is considered that the actual drying has been achieved.
3. Completely dry
Complete drying is the final stage in the paint drying process, also known as the curing stage. At this stage, the coating is fully cured and has all the mechanical and chemical properties for which it was designed.
Exterior features:The coating surface is completely dry and has the ultimate hardness, adhesion and chemical stability.
Time Requirements:Due to the long time required for full curing, the timing of the surface drying and the actual drying phase is typically the primary concern in coating production and application.
Assay method
1. Surface drying determination method
【Cotton ball blowing method】
According to the GB/T 1728-79 standard, "Paint Film and Putty Film Drying Time Determination Method", by placing the absorbent cotton ball on the surface of the coating and blowing the cotton ball with the mouth, if the cotton ball can be blown away without leaving fibers, the surface drying is achieved.It is suitable for evaluating the initial drying state of the coated surface, and is easy to operate, and is often used for rapid evaluation on site.
【Finger Touch】
Touch the surface of the coating film lightly with your fingers, if the coating film is not sticky to your hands and there is no greasy feeling, the surface is considered dry.A simple on-site judgment method, typically used on coarse or uneven coated surfaces.
【Small Glass Ball Method】
Place a small glass ball on the surface of the coating film and observe whether it can roll without sticking to judge that the surface is dry.It is used for smoother coating surfaces, and the surface hardening of the coating can be detected.
Actual drying determination method
【Filter paper pressing method】
Use a 200-gram drying Tester (drying weight) to press a piece of filter paper or a cotton ball on the coating film, and after a certain period of time, remove the Tester and observe the state of the filter paper or cotton ball to judge the actual drying.It is suitable for the mid-drying stage to assess whether the coating has dried enough, but has not yet fully cured.
【Blade Method】
Using a standardized scratching blade, scratch across the surface of the coating and observe the formation of scratches and the reaction of the coating to determine the actual state of drying.For harder coatings or laboratory assays that require high precision, the actual drying time can be more accurate.
【Thick layer drying method】
Apply a thick coating to the surface of the coating film and observe the drying time to judge the actual drying condition of the coating as a whole.Suitable for practical drying evaluations under specific needs, such as thick coat coating.
【Non-marking test】
Apply a slight pressure or force to the surface of the coating film and observe the reaction of the coating film to determine whether it has actually dried.It is used to evaluate the durability and drying state of the coating in actual use.
【Instrument Measurement Method】
Automatic drying time test instrument,The use of advanced instruments and technologies, such as paper tape method, hoop method, gear method, sand removal method, stitch method, etc., can achieve accurate measurement and recording of each stage of the coating drying process.Suitable for laboratory environments and applications where precision is critical, it provides detailed analysis of drying time and condition.
The drying process of coatings is a crucial part of coating application and quality control. By accurately evaluating and controlling the surface drying and actual drying phases of the coating, the performance stability and durability of the coating under different application conditions can be ensured. A wide range of measurement methods, from simple manual testing to sophisticated instrumental measurements, provide the coatings industry with a wide range of tools and technical support to help manufacturers and applications optimize efficiency and ensure coating quality in the production process.
