ASTM Glass Inspection Guidelines
Please follow these instructions when inspecting your glass upon delivery. This helps ensure everything meets our quality standards and gives you the chance to report any issues right away.
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This inspection process follows ASTM Standard C1036, which is the accepted industry standard for flat glass.
How to Inspect the Glass
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Stand 10 feet away from the glass.
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Look at the glass straight on—your line of sight should be at a 90-degree angle to the surface.
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Do the inspection in natural daylight, in direct sunlight.
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The main viewing area of the glass does not include the outer 2 inches around the edges when checking for blemishes or imperfections.
Understanding the Glass Zones
Divide the glass into three areas for inspection:
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Edge Zone – The 2-inch wide band around the outer edge.
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Main Zone – The large center area, which makes up about 80% of the glass.
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Rim Zone – The area between the Main Zone and Edge Zone (what’s left after removing the center and edges).
Blemishes and Pinholes
If a pinhole or small mark is easy to see during inspection:
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Main Zone: No pinholes larger than 1/16 inch are allowed.
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Rim Zone: No pinholes larger than 1/8 inch are allowed.
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In any 3-inch circle: No more than 2 visible blemishes.
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In any 12-inch circle: No more than 5 visible blemishes.
Scratches
If a scratch is clearly visible:
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Main Zone: Scratches up to 2 inches long are allowed.
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Rim Zone: Scratches up to 3 inches long are allowed.
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Edge Zone: Minor wear or abrasion is acceptable.
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Deep, heavy, or clustered scratches are not allowed (except at the edges).
Important Notes
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All X-ray lead glass has a natural yellow tint. This is normal and comes from the special materials used to block radiation (like lead and other heavy metal oxides).
If you have any questions about your order or the inspection process, please contact Lead Glass Pro right away. We’re here to help.