Generally speaking, a casing is flavoring and or ph adjusting flavorings that is absorbed into the tobacco. Toppings are flavoring compounds that are applied to the tobacco, but don’t soak in so much. Generally a base of propylene glycol and sometimes glycerin are used. Glycerin often adds the “creamy” smoke effect to a blend. 

Virtually all tobacco sold with the exception of whole leaf is cased. Most are topped, but not necessarily with additional flavors beyond the casing, since PG is the standard humectant for commercially produced tobacco and fungicides are often added at that step. 

The thing about all of this is it’s actually a pretty complicated discussion and I’ve only given a really basic explanation above. 

I have only played with casings, tinctures I made in ethanol (common drinking alcohol). I detailed some of my experiments in this thread:

https://www.tobaccoreviews.com/community/tobacco-talk/my-plum-tobacco-experiments/#post-4664

Also, most manufacturers don’t give much details or info on casings or toppings for obvious reasons, but if you watch this video, you’ll see tobacco being cased and topped. Sorry to non German speakers, but you will clearly see what is being done even if you can’t understand the language.

Hmmm… I can’t see the video Ted has posted. I hope I’m not posting the same one here 😊 Anyway, this is the one that educated me:

I found this video quite interesting, there are some good information concerning the additives the companies put in the pipe tobacco.

The amount of different tobacco blend in the video is huge, i mean, he had a hard work to put all info together, it worth to watch!