Lens colouring - a fine art 

Tinting (colouring) of lenses calls for genuine artistic sensitivity, excellent colour vision and a great deal of patience. Lenses react differently according to several different parameters (light, materials, tints, etc.).

Step 1 - Preparing the tint baths

The tints are produced using immersion baths. Pigments are meticulously weighed to obtain the desired tint with minimum retouching. This is a very delicate operation, since an additional half gram is enough to give the tint a different shade. The primary baths (red, blue and yellow), which are easier to prepare, give a more even coloration while still making retouching possible. Heated to 94 degrees celcius, the lens dilates, allowing the pigments to penetrate more easily.

Step 2 - Preparing the lenses

Lenses are sorted by substrate and tint. Their surfaces are then thoroughly cleaned to make sure they are free from any defect.

Step 3 - Lens coloration

The lenses are immersed in tint baths prepared to produce the desired shade. Some lenses are tinted to match a particular model, with the tint's final finish depending on a succession of immersions in different baths. The length of time they are immersed also has to be taken into account. For example, creating a class 3 tint requires between 12 and 40 minutes depending on the type of substrate, whereas a class 1 tint lasts around one minute. Primary colour retouching is carried out for most lenses. Colour perception does, however, vary according to corrective lens type. This is why model-based tints are very often created manually to match the required colour as closely as possible.

Step 4 - Quality control

The lenses are cleaned every time they are removed from the bath to eliminate any excess colorant. They are then visually checked, with the tint's intensity and evenness verified against a reference tint under a ceiling light that accurately reproduces daylight.

Step 5  - Baking

During this step, all the lenses are laid out on grids for the baking process.

Step 6 - Packaging or transfer

Once the manufacturing process is complete, the completed lenses are either transferred to the anti-reflective coating stage, or passed to the quality control department for checking and packaging prior to despatch to the customer.

© BBGR UK 2015