palatogram is an image of the region of the upper surface of the vocal tract
contacted by the tongue due to a consonant. The best way to obtain such an
image is to coat the tongue with a mixture of equal parts olive oil and
activated charcoal powder and record the resulting transfer of pigment.
The process is as follows:
- To protect the subject, one should use latex type gloves and
preferably a surgical mask.
- Mix the olive oil and the activated charcoal powder.
- Apply mixture to the speaker’s whole tongue with a paintbrush
or Q-Tip. NOTE: In case of dripping, one should cover the speaker’s
clothes before applying the mixture.
- Ask the speaker to produce a word that contains the target sound
(The word should not include any other sounds that make contact with the
- Use a mirror (preferably a sterilized inter-oral mirror), and
place it inside the speaker’s mouth at a 45O angle with respect
to the plane of the teeth.
Fig 1: Diagram showing relative position of
the elements required to record the palatogram.
- Use a camera or video camera to photograph the mirror’s
reflection of the place of articulation depicted by the imprint.
- If a video camera is used, the image can be transferred
directly to a computer for further processing as described in “How to Capture Video for use on the Mac.”
- Once the image has been recorded, have the speaker rinse out
his/her mouth with lemonade (or lemon juice in water).
Fig 2: Palatogram; still image digitized
from video. Orientation: Upper teeth are shown at top and
reflected in the mirror at bottom.