Published online by Cambridge University Press: 25 May 2016
Long-term trends in the infrared (JHKL) light curves of various carbon variables are described. Some stars, e.g. the semi-regular variables R Scl and GM CMa, show multiple periodicities; others, particularly the Miras with moderately thick dust-shells, show more erratic long-term changes. The light curves for R For, which have been intensively monitored over 20 years, show a pattern which is reminiscent of that seen for R CrB stars. This pattern is superimposed on regular large-amplitude Mira pulsations. The multi-periodic and erratic behaviour of these stars is compared with the predictions from various models.