Glass evaporating dishes (or crystallizing dishes) are pieces of scientific glassware that can be used to warm chemical solutions over time.
They can also help you evaporate solutions, solvents, or other supernatant liquids.*
What is an evaporating dish?
Glass evaporating dishes (or crystallizing dishes or watch glasses) are pieces of scientific glassware that can be used to warm chemical solutions over time. They can also help you evaporate solutions, solvents, or other supernatant liquids.*
Evaporating dish function:
- Storing samples
- Removing solvents
These pieces of laboratory glassware are particularly useful for removing extra solvents (like water or alcohol for example), leaving behind a concentrated substance.
There are many industries in which it is useful to leave just solid precipitates behind once solvents are removed. One common use is to run a trial or experimental version of a process before expanding the process to a larger scale.
Key attributes: durability and stability.
As you might imagine, evaporating dishes should be thermally stable and easy to clean.
While some use porcelain watch glasses in chemistry, we prefer borosilicate glass for its durability and corrosion/heat-resistant properties.
In a laboratory setting, the ability to (re)heat these dishes safely and effectively clean them after each use is paramount. You can heat these products with a bunsen burner or place them inside a vacuum oven without risking damage.
Speed up evaporation.
The unique shape of evaporation dishes aids in evaporation in two ways: the liquid inside has a large surface area, speeding up the evaporation process. The open top allows vapors to dissipate when compared to a more contained piece of glass like a beaker or flask.
In beakers, for example, condensation can occur on the vessel walls, impeding the evaporation of the liquid.
Evaporating dishes have multiple industry-specific uses such as decanting, storing samples, crystallization and more.
The most common use for this type of evaporating dish is for evaporating supernatant liquids. This lets you achieve crystallization of the solute dissolved in the solvent.
Conduct small-scale experiments.
A 100mm evaporating dish is a valuable staple as a means of testing ideas on a small scale. The built-in lip/spout makes for easy pouring.
Useful for quantitative analysis, these dishes are typically smaller in size and are perfect for running tests before extrapolating those results to a larger scale.
Once your theory has been tested, you can apply the same principles on a much larger, industrial scale through the use of one of our many rotary evaporators.
The addition of a vacuum to a rotary evaporator can make it somewhat safer than an open dish when certain combustible solvents are in use.
What is a “watch glass”?
A watch glass is very similar in function to an evaporating dish, with the only notable difference being that watch glasses tend to not have sides or rims and are more like a contact lens in shape.
The name of these items is derived from the idea that they resemble the glass covering of a wrist-watch.
What are supernatant liquids?
Supernatant liquids are liquids in which a compound has been dissolved. You can extract this dissolved compound later when the liquid is evaporated from the substance.
Note: We don’t recommend that you use a magnetic stir bar in conjunction with crystallizing dishes, due to the likelihood of splashing or spilling the (potentially hazardous) liquid inside.
For these processes, we recommend a closed top or more contained piece of glassware, such as a round bottom flask.