What properties should letterpress printing paper be tested for? What are the specific requirements?

Letterpress printing paper is a special paper used in letterpress printing. It is divided into roll paper and flat paper. Because of its good printability and opacity, it can be used for printing books, documents, and magazines.

Today we will introduce the testing requirements for letterpress printing paper stipulated in the QB/T 3524-1999 standard. Before testing, we need to divide the letterpress printing paper into B, C and D according to the quality.

Item detection

1. Quantitative: B grades are required to be within the three ranges of 52±2.5g/m², 60±3.0g/m², and 70±3.5g/m², and C grades are required to be within 52±2.5g/m² and 60±3.0g/m² Within these two ranges, if the D grade is within the range of 52±2.5g/m², it is considered to be up to standard.

2. Tightness: B, C, D, etc. must be less than or equal to 0.85g/m³ to meet the standard.

3. Whiteness: Requires grade B ≥ 65.0%, grade C ≥ 60.0%, grade D ≥ 55.0% to be considered up to standard.

4. Opacity: 52g/m² opacity ≥ 80.0%, 60g/m² opacity ≥ 82.0%, 70g/m² opacity ≥ 82.0% for B etc.; 52g/m² opacity ≥ 78.0%, 60g/m² for C etc. m² opacity ≥ 80.0%; D and other 52g/m² opacity ≥ 78.0% to meet the standard.

5. Smoothness: It is required that the average of the front and back sides of B etc. is ≥35s, and the difference between the front and back sides is ≤30.0%; If the difference between the two sides is less than or equal to 45.0%, it can be regarded as reaching the standard.

6. Fracture length: The longitudinal reel of B class is required to be ≥ 2.60km, and the average vertical and horizontal flat plate is ≥2.30; the longitudinal reel of C class is required to be ≥2.40km, and the average vertical and horizontal flat plate is ≥2.00; the longitudinal reel of D class is required to be ≥2.20km , Vertical and horizontal average plate ≥ 1.80, only to meet the standard.

7. Sizing degree: B, C, D, etc. are required to be ≥ 0.25mm, so as to meet the standard.

8. The vertical and horizontal average of the folding strength: it is required to meet the standard if the grade B is ≥ 4 times, the grade C is ≥ 3 times, and the grade D is ≥ 2 times.

9. Dirt Count: B etc. are required to be ≤160 in the range of 0.3~2.0mm², of which 1.0~2.0mm² black is ≤4 times, and no more than 2.0mm² is allowed; C etc. are ≤200 in the range of 0.3~2.0mm², of which 1.0~ 2.0mm² black ≤ 6 times, no larger than 2.0mm²; D grade ≤ 300 in the range of 0.3~2.0mm², of which 1.0~2.0mm² black ≤ 8 times, no larger than 2.0mm², it is considered to meet the standard.

10. Delivery moisture: B, C, D, etc. are required to be in the range of 4.0%~8.0%, so as to meet the standard.