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Glassware5 min

When a beaker should be borosilicate

Soda-lime is fine for a watch glass. Heat and repeated washing are why the rest of the bench is borosilicate 3.3.

Most glass on a working bench has to hold a liquid, survive a temperature change, and come out of a wash cycle clear. Borosilicate 3.3 is the usual choice because it expands less than soda-lime, so a warm beaker can meet a cooler bench with more margin.

That margin is not a promise. A chip on the rim, a star crack in the base, or a flask taken from a hot plate into a cold rinse will still fail. Look the piece over before you heat it.

Where other glass still belongs

Petri dishes, stirring rods, and Pasteur pipettes are often soda-lime because they are not the piece you set on a hot plate. A watch glass covers a beaker or holds a dried sample. It is not a heating vessel.

If a method calls for direct heat, move the work into borosilicate.

Read the mark

A Griffin beaker scale is for orientation. A Class A volumetric flask has one line and a stated tolerance. Using the beaker scale for a standard is how a prep drifts. Vitra prints material and class on each glassware page.