Types of Glass

Borosilicate (SCHOTT 8340)
The most commonly used glass is borosilicate. Sutter Instrument offers only TYPE I-CLASS A borosilicate as described by ASTM Standard 3.1.2* . This glass softens at 825 degrees Celsius and, as it is pulled, maintains its ratio of inside diameter to outside diameter over the total taper length. Borosilicate softens at a lower temperature than our other glasses and has a wider working range. These unique properties allow for a greater variety of shapes used in microelectrodes, patch pipettes, microinjection needles and, in the case of solid rod, chromosome dissection tools.

Aluminosilicate (SCHOTT 8252)
Aluminosilicate softens at a higher temperature (935 degrees Celsius) than borosilicate and is workable over a much narrower range. It has a tendency to continuously thin out as it is drawn which allows extremely fine tips with very short tapers. For example, we have pulled aluminosilicate tips in the 200-300 Angstrom range with taper lengths of 5-6mm. Its resistivity is several orders of magnitude higher than borosilicate, thus reducing leakage currents when used in ion-selective micropipettes. Aluminosilicate is harder than borosilicate which results in a pipette that is more suitable for penetrating tough tissues.

Quartz (Heraeus HSQ300)
The finest and purest glass available is quartz. It is superior to all other glasses in its mechanical, electrical and optical qualities. It has the lowest dielectric constant, the lowest loss factor and the highest volume resistivity making it ideal for patch clamp recording. Its chemical purity virtually eliminates leakage of ions** and by using quartz in single channel patch clamp recordings the lowest background noise levels have been achieved***. Due to its high melting point, it cannot be pulled on conventional pullers, but can be easily pulled with the Sutter CO2 laser-based P-2000.

* ASTM Designation E438-90 - April 1990.

** Zuazaga C., Steinacker A. Patch-clamp recording of ion channels: Interfering effects of patch pipette glass. News in Physiological Sciences: International Union of Physiological Sciences and the American Physiological Society: 5:155-158, August 1990.

*** Rae, James L., Levis Richard A. A Method for exceptionally low noise single channel recordings. Pflügers Archive; European Journal of Physiology:420:618-620, Springer-Verlag 1992.