Operation and Requirements of Drop Ball Test
The ball, which is 0.625 inches in diameter and weighs 0.56 ounces (16 grams), falls from 50 inches (127 centimeters) and hits the center of the lens. The geometrical center of the lens should be struck by the ball within a circle 5/8 inches in diameter. If the lens does not break, it is called a safety lens. There can't be anything that restricts the ball from falling. It cracks across the entire thickness, containing laminated layers (if any), and divides into two or more separate sections across the entire diameter.
How to Tell If Lenses Are Plastic or Glasses?
If you want to know if your glasses are made of glasses or plastic, the safest way is to ask the optician from whom you bought the glasses. If you do not want to ask the optician, there are several ways to differentiate them, such as sound, weight, and temperature.
Lightly tap the lens against your teeth or your ring. If the lens emits a high, ringing tone, it is a glasses. On the contrary, the plastic will have a low thud like sound when tapped.
Glass lenses are much heavier than plastic glasses and glass lenses feel colder to touch while plastic glasses feel warmer since it is a better insulator.
After learning what lenses you have, it is time to show how to remove coating from glasses.
How to buy contact lenses online?
Choose a standard retailer. Contact lenses belong to three types of medical device products, and the sale of contact lenses and their care solution belongs to medical behavior. No matter it is an optical shop or contact lens e-commerce website, it must have a Medical Device Trading Permit before it can be sold. The trend of buying contact lenses online is obvious, and there are a lot of websites of individuals and contact lenses that do not have business licenses. Therefore when the user buys a contact lens on the net, be sure to look for management qualification of Medical Device Trading Permit, guard against being cheated.
Recognize the identity
First of all, we should identify the logo of the pure titanium glasses frame. Usually, pure titanium glasses frame is on the supporting piece of the frame, and the inside of the temples is pure titanium.When online glasses need glasses retailers provide detailed pictures, to check if there is pure titanium.Usually, pure titanium frames are marked with 100% TITANIUM or PURE TITANIUM on the temples or lens.BetaTitanium stands are labeled BetaTitanium or β Titanium, which varies slightly from manufacturer to manufacturer.
Is it safe to buy contact lenses online?
Today's optometry is not a simple measurement of your degree. Through some professional instruments, they check the health of your eyes to see the health of your eyes. Is it appropriate to wear contact lenses at present? If there is inflammation in the eyes, it is forbidden to wear contact lenses, and if you wear them, it will cause harm to the eyes. If you buy online, you can't enjoy professional eye examination, try on, test, and other professional inspection and matching services that you can enjoy in professional stores, nor can you enjoy professional wearing and nursing guidance from professional staff. People often overlook eye problems that may result from the wrong choice of contact lenses, which are often overlooked by consumers.
Metal Eyeglasses
Whether you like classic looks or prefer rectangular and functional things, all metals will look new in 2021. Combining the trend of super large frames, you get a big round metal frame. These styles are not heavy and fit all face shapes, from round to square, and anything in between.
Cellulose Acetate
Acetate is a kind of thermoplastic resin obtained by esterifying acetic acid to acetic anhydride under the action of a catalyst. Acetate is resistant to water, gasoline, mineral oil, and lipids, weak alkaline solutions, and acids, excellent weather resistance, not resistant to ethanol, strong acids, and strong alkaline solutions. During thermoforming, it is very necessary to dry the material before forming. Acetate was born in the early 20th century, and was successfully trial-produced and industrialized by the UK in the early 1920s. At present, it is the second-largest variety in cellulose fiber after viscose fiber. Acetate can be used to make textiles, cigarette filters, film bases, and plastic products.
