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Deblocking is the process of safely releasing a spectacle lens from the temporary mounting fixture (the block) after the surfacing process is complete. This step must be done carefully to make sure the lens and its coatings are not damaged.
read more about deblocking in lens surfacing ...Two main methods are used. If the lens was secured using alloy blocking, the lens assembly is heated to melt the alloy, allowing the lens to simply float off. If the lens was secured using an adhesive pad, the lens is twisted or pulled carefully off the block.
Deblocking requires care because the lens is still relatively fragile. If the lens is pulled too hard or if the alloy is not fully melted, the lens can chip or break. It is also important that the residue from the alloy or adhesive is fully cleaned off the lens surface.
After the lens is released, the block is cleaned and prepared for reuse. If alloy was used, the metal is filtered and recycled. If an adhesive pad was used, the pad is peeled off and discarded.
Careful deblocking helps protect the investment in your backup lenses. Since this process prevents scratches or damage to the coatings, it supports the long-term clarity and quality of the vision correction you rely on when your contacts are out.
Yes, improper deblocking, especially if adhesive residue is left, can damage the anti-reflective coating if not cleaned properly.
The deblocking station for alloy is kept warm enough to melt the alloy, which is usually a very low temperature, but it is not excessively hot.
After deblocking, the lens is cleaned thoroughly and then sent to the edging department to be cut to the exact shape of the frame.
If you notice "cracks" in your lens coating that look like a spider web (crazing), it may have been caused by thermal shock during deblocking. This distortion can cause severe glare; your provider should replace these lenses under warranty.
Review of Optometry. Coating Failures in Eyewear (reviewofoptometry.com). 2024.
The Vision Council. Post-Processing Lens Care (thevisioncouncil.org). 2023.
ABDO. Spectacle Lens Finishing (abdo.org.uk). 2024.
Optical Laboratory Association. Safety and Cleaning (ola-labs.org). 2024.