...Does that mean the extracts don't saponify and therefore don't get calculated?
That's correct -- an extract doesn't saponify if the extract is water based or glycerin based.
If the extract is alcohol based, you might want to reconsider using it -- alcohol doesn't play nice with soap making.
If the extract is an oil, technically you should figure out what the carrier oil is and include that amount of oil in the calculations. If the amount you use is relatively small, however, it may be reasonable to just ignore this small bit of added fat.
The botanical material infused in the extract -- the chamomile essence so to speak -- isn't included in the calculations. It may react some with the alkali, but there's no way to know. Also the amount of "essence" is usually relatively small compared to the fats in the recipe, so its effect is small.
If so, how much extract would you recommend to add to 1 kg of oils?
I don't use chamomile in soap. I think many soapers would suggest 1 teaspoon to 1 tablespoon per 500 grams of fats for additives like this. Perhaps soapers who use chamomile will share what they do.
I read that the extracts should be added at trace, does anyone have an explanation as to why that is?
Some people are of the opinion that the lye is mostly used up by the time the soap batter reaches trace. They add ingredients at trace with the idea of "protecting" those ingredients from the lye. That has been shown to be incorrect -- NaOH and KOH are both is still highly active at trace.
Are there any special instructions with adding extracts to cp soap?
I'd probably add an extract to my fats, buzz with a stick blender briefly, then add the lye.
