Tinting and Tempering Flashcards
Why do colors look different under fluorescent light?
Fluorescent light operates primarily under a blue-green system with very little red, causing objects to appear blue-green. Natural light focuses on yellow, the center of the visible light spectrum, making objects have a natural look.
What are the three primary colors?
Blue, red, and yellow
Explain the difference between black and gray.
Density - pure black absorbs all light and reflects nothing back. Gray is black with layers of white on it, so it will reflect some of the light.
Why is tinting a science?
Tinting requires an understanding of the relationship of the dye chemistry to the physical properties of a lens. While there may be differing opinions on what is or isn’t a good color, there can be no argument that attempting to tint lenses without applying the proper methods and procedures will result in unpredictable colors and a substantial amount of frustration. In other words, there are many factors to tinting, such as temperature, color, time, etc., and they must all be understood to get the colors you expect, consistently, and with a minimal amount of effort.
Why are lenses heated in the tinting process?
Lenses are made from dense forms of plastic that are inherently resistant to absorbing dye particles. In order to color the lens, it is heated causing the surface to expand, thereby opening the pores of the material so the dye may enter inside and attach to it.
How does the temperature of the dye effect a gray lens?
If the temperature is too cold, the gray will have a red shift, and if the temperature is too hot, the gray will have a blue shift. The hotter the temperature, the faster the lens will draw the dye in.
What is the relationship between scratch resistance and tintability of a lens?
The more scratch resistant the coating is, the less likely it will be to accept dye.
Using Hi Index lens materials has what effect on tinting?
Hi index lenses usually come coated, meaning that only the back and edges can be tinted. They also draw blue more than other lens materials.
List four reasons two lenses might not tint the same color.
1.) The lenses may be different scripts and have a different thickness as a result.
2.) One lens is surfaced and the other is a stock uncut lens.
3.)The lenses are manufactured at different plants that use different processes.
4.) the lenses are not the same material
Why are gray and brown dyes hard to deal with?
Gray and Brown are the most requested tints, meaning there may be availability issues. They also are complex dyes, made up of different colors. If the colors aren’t mixed to the right proportions, the entire composition can be noticeably different. Also, different colors are designed for specific purposes, so it is important to know what to expect from each dye color to select the correct one.
What is the purpose of tempering glass lenses?
Glass lenses are required by law to be heat-treated or chemically treated to increase impact resistance.
If the glasses that are to be heat tempered are a different size and weight, describe what must be done to properly temper the lenses?
They must be tempered for different amounts of time, ensuring even uniform softening of the lens.
Describe what should occur if a tempered glass lens has been scratched or is flawed.
They should be replaced - a break in the surface tension is a point where the lens could fracture.
When time is essential, which method of tempering is advantageous?
Heat tempering - it can be accomplished in less than half an hour.
How can you verify that heat-tempering has been done to a glass lens?
A Maltese cross pattern will be visible in the lens when viewed in a polariscope - it indicates the surface tension was produced by heat tempering.
