Eye-Protection Indicator Testing for Exercise Books: D65 Brightness, Fluorescent Whitening Agents, a

Eye-protection indicator testing for exercise books evaluates critical optical and hygienic parameters such as D65 brightness, migratable fluorescent whitening agents, and ruling line contrast, in accordance with the mandatory Chinese national standard GB 40070-2021 and related ISO and GB test methods. This article explains the technical basis, sample requirements, testing items, analytical procedures, and practical applications of eye-protection performance evaluation for student workbooks. It serves as a practical reference for paper mills, stationery manufacturers, schools, and quality professionals involved in the myopia-prevention compliance of study supplies.

Technical Overview

Exercise books are among the most intensively used study supplies for children and adolescents, with students typically spending several hours per day reading, writing, and focusing on ruled paper at close range. Because the human eye continuously adapts to the luminance and color of the page, the optical properties of exercise book paper have a direct influence on visual comfort and visual fatigue. Excessively white paper, often achieved by adding large amounts of fluorescent whitening agents, produces high luminance contrast and increased short-wavelength reflectance, which can cause glare, eye strain, and accelerated fatigue during prolonged near-work.

To address this concern, China issued the mandatory national standard GB 40070-2021, Hygienic Requirements for Myopia Prevention and Control of Study Supplies for Children and Adolescents, which came into force on March 1, 2022. This standard establishes quantitative eye-protection requirements for exercise books, including an upper limit on paper D65 brightness and a prohibition on detectable migratable fluorescent whitening agents. Eye-protection indicator testing verifies whether exercise books comply with these requirements through instrument-based measurement of brightness, fluorescence, ruling contrast, and related optical properties.

Testing is typically performed by accredited third-party laboratories using spectrophotometric, densitometric, and extraction-based analytical techniques, supported by internationally recognized reference methods such as ISO 2470-2, ISO 2471, ISO 8254, and the corresponding GB/T method standards. The resulting test reports are widely used for regulatory compliance, product certification, school procurement tenders, and marketing claim substantiation.

Testing Samples

Finished Exercise Books

Complete exercise books intended for student use form the primary sample category, including lined composition books, grid books for mathematics, four-line books for language learning, blank drawing pads, and multi-subject workbooks. Both the paper substrate and the printed ruling are evaluated, because eye-protection performance depends on the interaction between paper background reflectance and ruling line darkness. Representative samples should be taken from the same production lot, kept clean and flat, and protected from light, moisture, and contamination before testing.

Notebook Refill and Loose-Leaf Paper

Loose-leaf refill sheets, binders, and replacement paper cores sold as accessories for reusable notebooks are also within the scope of eye-protection evaluation. These products are tested using the same optical criteria as finished exercise books, since students use them under identical reading and writing conditions. Sufficient sheet quantities, typically several dozen sheets, are required to assess brightness uniformity across the production lot.

Sample Conditioning

Prior to measurement, samples are conditioned in a controlled atmosphere of 23 ± 1 °C and 50 ± 2% relative humidity in accordance with ISO 187 and GB/T 10739. Proper conditioning stabilizes the moisture content and dimensional state of the paper, ensuring that optical measurements are reproducible and comparable between laboratories.

Testing Items

D65 Brightness

D65 brightness, also known as D65 diffuse blue reflectance factor, is the core eye-protection indicator for exercise book paper. GB 40070-2021 requires that the D65 brightness of exercise book paper shall not exceed 85.0%. Papers well below typical high-white commercial grades are preferred, because moderate brightness reduces luminance contrast between the page and the surrounding environment, thereby lowering glare and visual stress during sustained reading and writing.

Migratable Fluorescent Whitening Agents

Fluorescent whitening agents absorb ultraviolet radiation and re-emit blue light, artificially increasing apparent whiteness. Besides creating an excessively bright page, certain migratable residues may transfer through skin contact. GB 40070-2021 stipulates that migratable fluorescent whitening agents shall not be detected in exercise book paper, making this a pass/fail safety and eye-protection criterion.

Ruling Line Print Contrast and Clarity

The visual clarity of ruled lines relative to the paper background determines how easily students can track lines while writing. Insufficient contrast forces the eye to work harder to locate the ruling, while excessive contrast can be visually harsh. Testing evaluates the reflectance difference between the printed ruling and the unprinted paper, along with the uniformity, continuity, and edge sharpness of the printed lines across the entire page.

Opacity and Show-Through

Opacity measures the ability of the paper to prevent printed content from one side being visible from the other side. Low-opacity paper produces show-through of ruling and writing, which degrades reading comfort and increases visual interference. Opacity is evaluated as a supporting indicator of overall page visual quality.

Supplementary Optical Indicators

Depending on the evaluation purpose, additional indicators may be assessed, including surface gloss, which influences specular glare under desk lamps and classroom lighting; chromaticity and tint, which characterize whether the paper is neutral or excessively blue-shifted; and brightness uniformity across the page and between sheets, which affects consistent visual perception during use.

Testing Methods

Eye-protection indicator testing combines standardized optical measurement with chemical extraction analysis. The general workflow is as follows:

• Sample preparation: Exercise books are unpacked, and test pieces are cut from specified areas of the pages, avoiding printed margins, stamps, and damaged regions. Duplicate specimens are prepared for statistical reliability.
• D65 brightness measurement: Brightness is determined using a reflectance spectrophotometer with diffuse illumination geometry and D65 illuminant, consistent with ISO 2470-2 and the measurement method annexed to GB 40070-2021. Results are reported as the mean D65 blue reflectance factor and compared against the 85.0% upper limit.
• Fluorescent whitening agent screening and confirmation: Specimens are first screened under ultraviolet illumination at 365 nm to identify fluorescent emission. Positive or ambiguous results are confirmed by aqueous extraction followed by ultraviolet spectrophotometric or fluorescence analysis in accordance with GB/T 27741, with the detection threshold defining the not-detected criterion.
• Ruling contrast measurement: The reflectance of printed ruling lines and adjacent unprinted paper is measured with a spectrodensitometer or reflectance photometer. Print contrast is calculated from the reflectance ratio, and line uniformity is assessed through multiple measurements distributed across the page.
• Opacity and gloss measurement: Opacity is measured by comparing reflectance over a black backing against a stack of identical sheets, per ISO 2471 and GB/T 1543. Gloss is measured with a specular glossmeter at defined geometries per ISO 8254 and GB/T 8941.
• Data evaluation and reporting: All results are statistically evaluated, checked against the applicable limit values, and compiled into a test report stating the sampling basis, methods used, measured values, and conformity conclusions.

Throughout the process, instruments must be calibrated with certified reference standards, and laboratories are expected to operate under recognized quality management and accreditation systems to guarantee the validity and mutual acceptance of results.

Applications

• Regulatory compliance: Demonstrating conformity with the mandatory requirements of GB 40070-2021 for exercise books placed on the Chinese market, including use in market surveillance inspections.
• Manufacturer quality control: Paper mills, printers, and stationery brands use eye-protection testing during product development, incoming paper inspection, and routine release testing to control brightness, fluorescence, and ruling quality.
• School and government procurement: Education authorities and schools increasingly require eye-protection test reports in tender documents to ensure that purchased exercise books meet myopia-prevention hygienic requirements.
• Product differentiation and claim substantiation: Brands marketing exercise books as eye-friendly or low-glare rely on third-party test data to support labeling claims and to build consumer trust.
• E-commerce and retail verification: Online platforms and retailers may request test reports to verify that listed study supplies comply with applicable eye-protection standards before sale.
• Research and product improvement: Data from optical testing guide the optimization of pulp formulation, dyeing and shading strategies, and ruling ink selection to achieve comfortable, compliant page appearance.

FAQ

Why is very white paper considered harmful to children's eyesight?

Extremely white paper usually contains high levels of fluorescent whitening agents that boost short-wavelength reflectance. The resulting page appears glaring under normal lighting, increases luminance contrast against the surroundings, and can accelerate visual fatigue during prolonged near-work. Capping D65 brightness at 85.0% keeps page luminance within a comfortable range.

Is compliance with GB 40070-2021 mandatory for exercise books?

Yes. GB 40070-2021 is a mandatory Chinese national standard that took effect on March 1, 2022. All exercise books sold in China for use by children and adolescents must satisfy its hygienic requirements, including the D65 brightness limit and the non-detection of migratable fluorescent whitening agents.

What does "not detected" mean for migratable fluorescent whitening agents?

It means that when the paper is extracted under standardized conditions and the extract is analyzed by ultraviolet spectrophotometry or fluorescence measurement, the fluorescent whitening agent content falls below the detection limit of the specified method. This is a pass/fail criterion rather than a numerical limit value.

How many samples are required, and what is the typical turnaround time?

Common practice is to submit at least ten finished exercise books or a comparable quantity of refill sheets from the same production batch. Testing is usually completed within five to ten working days after sample receipt, depending on the number of indicators requested and laboratory workload.

Are test reports from accredited third-party laboratories accepted in procurement tenders?

Yes. Reports issued by accredited third-party laboratories that meet the applicable national accreditation and metrology requirements are widely accepted in school procurement, retail audits, and regulatory submissions, provided the testing scope covers all indicators required by the relevant standard.

Can the same testing scheme be applied to textbooks and other printed study materials?

Yes. GB 40070-2021 covers a range of study supplies, including textbooks, teaching aids, children's reading materials, and study magazines. While the specific limit values differ by product category, the measurement principles for brightness, fluorescent whitening agents, and print contrast remain the same.