Goniometer (Rame-Hart A-100) - Operating Procedure

System Illustration

The Ramé-Hart A-100 Contact Angle Goniometer and relevant adjustment knobs.

Measurement Procedure

To measure the contact angle of water on a surface, perform the following procedure.

• Note that the image through the scope is inverted upside-down.
• You will also see a reflection of the water droplet on your polished substrates, as illustrated here:

View through the scope: Illustration of a reflective sample. Substrate is on top due to inverted image.

Alternate Measurement Technique - Tilt Angle

An alternate, "quick and dirty" method for comparing hydrophobicity between surfaces is to drop an identical amount of water on each sample's surface, and tilt the sample until the drop rolls off - the tilt angle required can be compared. This technique is much more "noisy" than the goniometer, but can be done without highly specialized equipment.