What is the function of incense and candles to a meditation practice? Are they used in all types of meditation or only some types?
Incense and candles are not essential to a meditation practice. They can aid in concentration, but they can also become an emotional crutch if we become attached to them. I did the ritual of lighting candles and incense during my practice for a few weeks, and quickly got tired of it.
If you are practicing vipassana (a.k.a insight meditation) as opposed to samatha (a.k.a tranquility meditation) then it's really not necessary to create that kind of environment. In fact in vipassana we want to become free from external dependencies, so creating a certain type of environment might actually be counterproductive to the practice.
I'm one of Venerable Yuttadhammo's students, and he teaches vipassana in the Mahasi Sayadaw tradition. Check out his videos and/or book if you haven't already.
Unfortunately I can't comment on samatha practices, as I haven't been taught in that area.
Incense sticks, especially sandalwood ones are good cleansers. They cleanse the entire room or the surrounding area, preparing the area for a peaceful meditation or prayer. Not only for prayer, burning incense in rooms used by patients or emotionally affected places also helps in cleaning the energy in those areas.
Candles or Lamps
While incense is used for cleansing, candles, lamps and other lights energize the surrounding area. Lit lamps are considered a symbol of enlightenment in many traditions.
Both of these when used in a meditation hall provides the perfect environment for a peaceful and fruitful meditation.
Hope this answer helps you. :)
It depends on what you're goal is with meditation. There are different meditations and people meditate with different motivations and goals. With some goals incense is useful. With others it can be a hindrance. As meditation is experiential you can actively map or watch your own state of consciousness to see what the incense is doing. Is it helping or hindering?
There needs to be a distinction made between those who are meditating to be calm and relaxed, to feel better and those who are trying to move into states beyond all mental fluctuations. They are different enterprises.
I've been taught that meditation is fundamentally about involution of consciousness (turning consciousness inwards). As you go deeper you move away from the part of the mind that is related to the five senses. You enter deeper states of inner silence. Sensory input makes your mind react this inner silence is affected by fluctuations of your mind.
Incense affects your sense of smell which is a very basal sense. It goes deep into your brain. This results in deeply rooted reactions in the mind. Incense thus produces mental fluctuations which limits your ability to enter no mind states. Note that some people meditate in darkness with no sounds or smells to help the process of involution. The senses are starved of stimulus. So if your goal is to move beyond mind into complete silence then incense may hinder you as it stimulates the smell sense resulting in mental fluctuations at a deep level in mind.
Alternatively some incense has a calming effect on the mind and many people use it to achieve a sense of calmness and relaxation. So if you are meditating for calmness and relaxation then it could help you. Clearly Buddhism uses incense for many practices and rituals. But do Buddhist practitioners who are attempting to reach states of no mind use incense?