7004 - Drawn glass and blown glass, in sheets, whether or not having an absorbent, reflecting or non-reflecting layer, but not otherwise worked:

Heading 7004 encompasses drawn glass and blown glass that are manufactured in sheet form. This classification is specifically for glass that has undergone processes such as drawing or blowing to achieve its sheet configuration. Importantly, the scope of this heading includes sheets that have an applied layer, such as those that are absorbent, reflecting, or non-reflecting. However, it is crucial to note that any further working of the glass beyond these initial processes, beyond the application of such layers, would generally result in classification under a different heading.

To distinguish this heading from its siblings, it's important to recognize that heading 7004 deals exclusively with glass in *sheet form* produced by drawing or blowing. Other headings within Chapter 70, and indeed Section XIII, cover a vast array of materials and finished goods. For instance, headings for cast or rolled glass (e.g., 7003) will have different manufacturing processes, while headings for worked glass (e.g., 7005, 7006, 7007) will include glass that has undergone cutting, shaping, or further treatment beyond the initial sheet formation and layering. This heading is also distinct from raw glass materials or glass articles not in sheet form.

Within heading 7004, two primary subcategories exist to further refine the classification based on the glass's appearance or treatment. Subheading 7004.20 covers glass sheets that are colored throughout the mass, opacified, flashed, or possess a specific functional layer like an absorbent, reflecting, or non-reflecting coating. Subheading 7004.90, conversely, is a residual category for all other drawn or blown glass sheets that do not meet the criteria for 7004.20, effectively capturing plain or "clear" drawn and blown glass sheets.