Lens Blocking with Low Melting Point Alloys

Widely used throughout the world, MCP introduced low melting point alloys to the optical industry around 20 years ago as a simple, effective and economical lens blocking solution. Offering a higher compressive strength than resin or wax alternatives, these reusable bismuth based alloys also have a longer shelf life than other blocking materials.

A range of five lens blocking alloys is now available from the company, and includes formulations suitable for all lens types.

All have a melting point of 70°C (158°F) or below, and are therefore simply melted away from the lens using hot water, eliminating the possibility of distortion.

Lead and cadmium free MCP 61 is the newest formulation with a melting point of 62°C (144°F). Cadmium free MCP 58, the most stable alloy in the range, melts at 58°C (136°F). Both of these alloys are suitable for use with plastic and glass lenses.

MCP 47 is used widely in the industry for blocking plastic lenses and has a melting point of just 47°C (117°F). Other alloys in the range include the traditional formulation for glass lenses - MCP 70, (70°C or 158°F).

Each of the alloys has a compressive strength of 15-30 Mpa for 0.2% set, which is easily sufficient for the necessary rigidity and control in all locating and centring operations.

MCP melting pots are available for melting, holding, dispensing and recovering the alloys at exactly the right temperature and under the safest working conditions.

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