What type of glass are Pasteur pipettes made of?

Question

What type of glass are Pasteur pipettes made of? And at what temperature do they need to be heated to create a micro-pycnometer?

Answer 1

This page from the glass shop in the Department of Chemistry and Biochemistry at the University of Delaware lists the properties of several common glasses that are used in laboratory equipment.

The two most common types of glass for less expensive applications are soda lime glass and borosilicate glass. The anneal point (or glass transition temperature) can be thought of as the temperature above which the glass can start to have some molecular motion, but it is not a liquid. The soften point is probably what you are looking for.

$$ \begin{array}{lcc} \hline \text{Glass} & \mathrm{Anneal\ Point\ ^\circ C} & \mathrm{Soften\ Point\ ^\circ C} \\ \hline \text{Soda Lime} & 545 & 724 \\ \text{Borosilicate} & 560 & 821 \\ \hline \end{array}$$

Soda lime glass is cheaper, and is generally used when you want something very inexpensive or disposal. Borosilicate glass has a lower thermal expansion coefficient so it is less likely to break. If you want to know which type of glass your pipets are made from , look at the wide end from an angle. If there is a slight greenish cast to the curve of the glass, you have soda-lime glass. Or you could look at the box they came in.