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D6488-08 – Standard Test Method Technical Guide
🎯 Introduction and Scope of D6488-08
The ASTM D6488-08 (Reapproved 2020) standard provides a common set of definitions for print problems resulting from deficiencies in ink, substrate, or press. It covers three major printing processes: lithography, flexography, and gravure. The standard is essential for improving communication among ink makers, substrate manufacturers, and printers.
According to Section 1.1, these definitions address problems that develop as a result of deficiencies in the ink, substrate, press, or combinations thereof. Section 3 emphasizes that a common set of definitions is crucial to avoid misunderstanding.
🖨️ Key Lithographic Printing Defects
The following table lists common lithographic printing defects defined in the standard, along with their primary causes.
| 🟦 Term | 📏 Definition | ⚡ Primary Cause |
|---|---|---|
| Blistering | Formation of small air pockets under the printed paper surface. | Moisture trapped under dried ink film during heatset drying. |
| Blocking | Undesired adhesion between printed sheets under pressure or temperature. | Improperly dried ink or coating. |
| Bronzing | Metal-like reflectance on nonmetallic materials at specular angle. | Reflectance from pigment particles at ink film surface. |
| Catch up | Non-image area of plate becomes ink receptive. | Insufficient dampening solution feed. |
| Coating pick | Removal of coating particles from the sheet surface. | Ink tack exceeds surface strength of substrate. |
| Dot doubling | Unintentional printing of two images slightly out of register. | Mechanical movement between plate and blanket. |
📊 Significance of Standardized Terminology
The standard plays a vital role in the print industry by providing clear definitions. It covers terms like crocking, dot distortion, and others. The term “paper” includes paperboard, as noted in Section 3.2. Definitions from referenced sources are indicated by acronyms, such as [GATF] for catch up.
💡 Note: The term “paper” in this standard encompasses paperboard, making it applicable to a wide range of substrate materials.
⚠️ Important: Blistering is more common with higher ink coverage and heavier basis weight papers. Proper heatset drying control is essential.
❓ Frequently Asked Questions
🔍 What is blistering in printed matter?
Blistering is defined as the formation of small air pockets under the printed paper surface. It results from moisture being trapped under the dried ink film during heatset drying, and it is more common with higher ink coverage and heavier papers.
💡 How is bronzing characterized?
Bronzing is a metal-like reflectance at the surface of nonmetallic materials, perceived at the specular angle. It is caused by selective reflectance from pigment particles that have separated from the vehicle at the ink film surface.
⚡ What causes catch up in lithography?
Catch up is a condition where the non-image area of the plate becomes ink receptive due to insufficient feeding of dampening solution. It is related to scumming.
📌 What is dot doubling?
Dot doubling is the unintentional printing of two images slightly out of register from a single form