In chemistry, a watch glass is an item of laboratory equipment consisting of a circular, slightly concave piece of glass. It is used to evaporate liquids, cover beakers, and hold small samples during weighing.
Watch glasses come in a variety of materials, ranging from inexpensive acrylic to more expensive sapphire and mineral glass. Each has its own pros and cons. Choose one that makes the most sense for your situation and budget.
Laboratory Glassware
Laboratory glassware is used to store chemicals, transfer liquids, make solutions, and measure reagents. It is generally made from borosilicate glass and can be resistant to heat, corrosion, and chemical attacks. It is also easily shaped by skilled scientists who can design bespoke items for specific experiments.
It is important to clean and maintain laboratory glassware carefully to ensure it stays in good condition. This will help it to continue working efficiently and safely, as well as protect the integrity of your work.
The first step in cleaning laboratory glassware is to empty and thoroughly wash it with detergents, preferably with anti-bacterial properties. This process removes any dust or other contaminants, which can affect the performance of your instrument.
Next, rinse the contaminated glassware with water, using several full rinses to eliminate all residue. This is particularly important for instruments with a meniscus, as residues and other contamination can contaminate the measuring area and impair accuracy.
Some laboratories conduct a soaking process to dissolve any previous reactants that may have affected their glassware. This involves adding a mild alkaline or acid solution, such as 1% hydrochloric or nitric acid. This soak should be conducted for a minimum of four hours before the final wash and rinsing processes are completed.
When the soaking process is complete, laboratories often conduct multiple soap and water washes with a variety of cleaning products, followed by many more full rinses. This helps to remove any remaining cleaning agents, as well as any dissolved residues and grease.
During this process, it is essential to use only plastic core brushes with soft non-abrasive bristles or soft sponges/rags. Avoid the use of abrasive materials as they can damage the surface and reduce the strength of the glassware.
After the final wash and rinsing, it is imperative to dry the glassware carefully. It is best to use an automatic dryer if possible or to put it in a fume hood to help speed the drying process.
Laboratory glassware is vital to any chemistry lab, and its proper handling is essential for the safety of all involved in the experiment. Incorrect handling can seriously weaken the material and lead to breakage in the long run.
Pyrex Watch Glass
A watch glass, or evaporating dish as it is commonly known, is a round concave glass plate used in chemistry to evaporate liquids. These labware items are typically made from Pyrex (also called borosilicate glass), which is a type of crystalline material that is heat resistant and chemically inert. This glass is ideal for evaporating chemicals, boiling liquids, or covering a hot beaker.
There are a number of different glass types on the market today, but most come in one of two main forms: tempered or untempered. The tempered type is the favored choice, thanks to its superior temperature tolerances and thermal shock resistance. The untempered version is a little less rugged and more susceptible to breakage, but can still be put to good use in some scientific applications.
Cleaning a watch glass can be tricky. While a microfiber cloth and a good detergent can usually do the trick, more delicate specimens may require an extra measure of care. First, you should try to remove the majority of the grit that has been collected on it. Then, rinse the glassware with a mild soap solution, making sure to rinse out the corners. Then, you can use a small amount of acetone to remove any leftover residue. This will leave the glassware looking sparkling clean.
The best way to keep your pyrolytic glassware looking new is to avoid the occasional scrape or bump and regularly check for signs of wear, such as scratches or discoloration. If this is not possible, a light coat of clear glass cleaner can make things look brand new again.
There are many ways to keep your labware in tip-top shape. For example, never forget the oh-so-old rule: heat and cool slowly to avoid causing breakage. In addition, keep a few pairs of laboratory gloves on hand to protect your hands and avoid slipping and falling while performing a test. Lastly, the most important piece of advice is to take the time to understand your equipment and what it can do for you. With that, you’ll be able to get the most from your labware and ensure you have the highest quality product for your needs.
Laboratory Beaker Covers
Laboratory beaker covers are used to protect beakers and flasks when they’re not in use. They are often made from glass (such as borosilicate glass), but can also be made from certain plastics, such as polyethylene or PTFE.
Beaker cover glass is typically more expensive than general-purpose glassware. It’s designed to withstand higher workloads, so it’s important to choose the right type for your needs.
Some glass beakers are made from borosilicate, which is a very chemically resistant material. This makes them a good choice for storing and processing acids, alkalis, and salts. However, they’re not entirely inert and can absorb dyes, stains, and proteins.
You can also find laboratory beaker covers in a variety of other materials, such as metal or plastic. These products are less expensive than glass, but they may not be as durable.
These lab beaker covers are designed to protect beakers from vapors, which can be dangerous when the lids fall off. They’re ribbed to eliminate vapor escape and have fire-polished edges.
They are ideal for evaporating liquids or growing seed crystals. They can also be used to hold small samples for observation under a microscope or as spore collectors in printmaking.
Be sure to follow standard safety procedures when handling watch glasses, including wearing gloves and a lab coat. You can even place a fume hood over the glassware, so you don’t inhale any chemicals.
To keep the watch glass safe, you should always clean it thoroughly and maintain it properly. This will help to prolong its lifespan and protect the validity of your work.
First, rinse the glassware in distilled water to remove any organic residues. If there are any metals or alloys on the glassware, you should also soak it in a solution of sodium hydroxide or potassium hydroxide.
Soak the glassware in the solution for several minutes and then rinse it with distilled or deionized water. This will make it easier to clean.
Repeat this process until all the contaminants are removed from the glassware. If necessary, you can re-sterilize the glassware using a base bath (saturated NaOH or KOH solutions in ethanol, methanol, or isopropanol).
This should ensure that the beaker is 100% quantitatively clean and ready for use. You can also remove any ground glass joints with a specialty task wipe soaked in acetone or hexane.
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Laboratory Evaporating Dish
A laboratory evaporating dish is a shallow open container used for the evaporation of solutions and supernatant liquids to produce a concentrated solution or solid precipitate. They are commonly made of borosilicate glass or porcelain, but some of these dishes are also crafted from refractory metals such as platinum for very high-temperature work.
They look like small bowls, and some of them have a pour spout for easy sample transfer. These lab dishes can be used for a variety of procedures, from the evaporation of aqueous solutions to the determination of the silicon content in organic samples.
During this process, the dish is heated with a Bunsen burner to induce evaporation and remove water from the mixture. The dish can be weighed and the weight of the evaporated substance subtracted from the original sample to obtain an accurate analysis.
Most evaporating dishes are made of borosilicate glass or glassy carbon, which are non-reactive and can withstand heat from a Bunsen burner. Some evaporating dishes are also made of porcelain, which is heat-tolerant and does not deteriorate with repeated heating.
When washing evaporating dishes, be sure to thoroughly rinse the dish with tap water and then follow up with 3-4 rinsings of deionized water. If the dish has a base, you may need to soak it overnight in soapy water before washing it.
It is important to properly clean and maintain evaporating dishes to ensure their reliability for quantitative lab use. Pipets, volumetric flasks, and burets need to be cleaned regularly in hot soapy water to remove bacteria and fungi from the inside of the ware.
Rinse the ware with the appropriate solvent for the contents of the dish, then clean the inside with a brush or sponge, if necessary. Dry the ware with a clean cloth or towel. If the ware is porous, gently warm it over a Bunsen burner flame or on a hot plate.
Before storing evaporating dishes, they should be completely dry and free of residue or dirt. If they need to be stored in the refrigerator, allow them to air-dry before putting them away.
