In previous articles on footwear product labeling, it was mentioned that both the domestic standard QB/T 2673-2023 and the international standard DIRECTIVE 94/11/EC stipulate that the material labeled for the upper should account for at least 80% of the surface area of the upper. If no single material reaches 80%, at least two main materials should be labeled. The labeling method has been introduced before, but how to calculate whether the material reaches 80% of the surface area?
Currently, there is no national or international method specified for calculating the proportion of shoe upper material area. In past measurements, methods such as high-end 3D scanning, shoe upper projection, and simple grid methods have been used. In 2022, the China National Trade Promotion Association, referencing standards such as “GB/T 2703-2017 Footwear – Terminology” and “GB/T 24988-2020 Copy Paper,” developed a group standard with the code T/OTOP 1011-2022, which was implemented on March 15, 2022. This method is highly practical and straightforward. Today, we will introduce this method.
1. Test Principle
The shape of the shoe upper is proportionally photocopied onto white paper using a scanning device. By weighing the mass of the white paper corresponding to each material, the proportion of each material’s surface area on the upper is calculated.
2. Test Equipment
– Scanning device capable of clearly photocopying the object onto white paper.
– White paper, A4 or A3 copy paper with a basis weight of not less than 80.0 g/m², meeting the requirements for qualified products in GB/T 24988-2020.
– Cutter/Scissors
– Analytical balance with a precision of 0.0001 g.
3. Sample
A pair of complete shoes.
4. Test Steps
– Separate the upper and sole of both shoes along the welt.
– Remove attachments or reinforcements, such as logos, piping, decorations, decorative materials, laces, lace buckles, assembled tongues, eyelet pads, or similar attachments.
* Note: If these materials are difficult to remove, they may be left in place, but the test results should not consider these materials.
– Flatten the upper on the test bench. If any part cannot be flattened, cut it open to ensure the upper is flat and each part can be fully photocopied onto white paper.
– Place the flattened upper in the scanning device and start the device to photocopy the complete upper image onto white paper, with two copies for each shoe.
– Leave the photocopied white paper at room temperature for at least 30 minutes.
– First, cut out the white paper along the outer contour line of the upper, then cut along the curves where different materials meet, and categorize the paper by material type.
– Weigh the total mass of the cut white paper corresponding to each shoe, denoted as M. Then weigh the mass of the white paper corresponding to each different material, denoted as mi.
5. Result Calculation
Calculate the proportion of the upper material according to equation (1):
In the equation:
W represents the proportion of the upper material, expressed in percentage (%);
Mi represents the mass of the white paper corresponding to each material, in grams (g);
M represents the mass of the white paper corresponding to the entire upper, in grams (g).
Note: The difference between the two test results for the same shoe should not exceed 5% of the arithmetic mean; otherwise, the test should be repeated.
Although this method is highly operable, it requires cutting the upper from the shoe. For shoes that must not be damaged or have special designs, this method still has some limitations. In such cases, we can refer to the principle of this method and use a tracing approach to measure the proportion of different materials on the shoe upper.
For more information on footwear testing, please feel free to contact us.
