Coloring Plastic Lenses, Section 1

MIXING BPI® TINTS.
9 EASY STEPS TO PERFECT LENSES

1. BPI® Molecular Catalytic™ tint is shipped in a liquid concentrate. The concentrate has many chemicals that reduce surface tension, suspend tint and cure the plastic lens more fully. Even diffusion of tint molecules ensures the bright, vivid colors rendered by BPI® tints.

2. Water conditions will vary from place to place and could cause difficulty in dispersing certain pigments. Distilled water is not usually necessary for mixing BPI® tints, but may help in certain locations. When using tap water, let the water stand for a while to remove the chlorine and settle the sediment.

3. The dilution factor for BPI® tints is approximately 10 parts water to 1 part tint concentrate. One 3-oz. bottle will make 1 quart of tint solution. A complete bottle should be used each time. Be sure to shake bottle well to ensure proper mixing of pigments; this is especially important for gray, brown and green tints.

4. Pour the tint into a half-filled tank of warm water, but not above 140°F., since too high a temperature may prevent even mixing of the tint. Rinse the bottle well with additional water, being sure to remove any of the tint pigment from the bottom of the bottle. Pour into tint tank. If all the pigment is not removed, the tint solution will not achieve the standard color. Fill tank with additional water to the proper working level.

5. After the contents of the tint bottle have been emptied into the color tank, bring the temperature up to 200-210°F. The increase in temperature should not be done in less than 10 minutes. Fast heat up will prevent some tint from completely dissolving. Too fast an increase can also cause agglomerations and tint crystallization, which will change the color and shortens its life. Repeated heating in direct contact with heating coils or flame may also shorten tint life. Always use a good thermometer to check tint temperature.

6. Lens Prep II* is an important ingredient in the Molecular Catalytic™ tint systems. It ionizes the lens positively with a special coating that allows it to exhibit a charged interface opposite to that of the tint. This potential difference attracts the tint ions to the lens surface for fast color absorption. Lens Prep II™ is a concentrate and should be diluted approximately one ounce to 32 ounces of water. Be sure not to use too much, or else streaking will occur because of the unevenness of the positive charge on the lens.

7. The Molecular Catalytic™ tints should not be used with any lens holders that are not stainless steel or Teflon. The heating containers should be stainless steel, heat resistant glass or plastic. All BPI® Molecular Catalytic™ Tints work on an additive basis which allows one color to be combined with others.

8. The length of time that a tint lasts depends primarily on the length of time it has been hydrated with water; secondly on the temperature; and finally, on the number of lenses that have been colored. As time goes by, the number of lenses that can be tinted decreases. The greatest decrease is in the gray, brown, and green tints. Blue, pink and yellow have a longer life span. As the tint solution is used, the water in the solution will evaporate. The water loss can be replaced with warm water whenever the level is low.

9. Each time the tints are reheated, be sure to stir the tints well before heating, and again when the tints are warm. An occasional stir after the tints are hot is strongly suggested.

OPERATIONAL HINTS: CORRECT USE OF YOUR LENS TINTING INSTRUMENT

When first turning on your unit for the day, set your thermostat to about half scale. When thermal stability is reached (15-30 minutes depending on unit size), your thermostat indicator light will go out.
Now you can gradually increase the temperature until the TINT SOLUTION itself is 200-210° F being mindful that the boiling point of the tint solution is the same as water, 212°F. Your thermostat setting, which relates to the temperature of the heat transfer fluid in your system, will be different from the actual temperature of the tint; for that reason, a good lab quality thermometer is a wise investment.
Avoid the use of mercury thermometers, however, as their breakage constitutes a health hazard. Remember, the hotter the tint, the faster and more uniform the results.
While your unit is on, do NOT leave your lids on, as you may have a messy boil-over to contend with from the rapid increase in pressure and temperature. Also, avoid immersing the lens holders and other utensils rapidly in the tint solution as a foam-up reaction may be caused by breaking the surface tension too rapidly.
To minimize evaporation, you may idle your machine at 130°F. and leave lids on. Remember, only the water evaporates, not the tint. Water may be added as needed to maintain proper operating level.
Make it a habit to wipe up spills immediately, especially those on the BPI® Color Matching Plate™, with a damp cloth.