Why do some FO work in soy wax and others do not?

[AudraT]

Why do some fragrance oils work well in soy wax, or any wax really, while other fragrance oils not work at all? If I purchase FO's from the same company, use the same percentage (10%), the same wicks, and in the same wax, why do some fragrances have a wonderful hot throw while others have none at all? What's the chemistry that's going on here?
Another related question, why can you only smell some candles when you are directly over the flame but any further away than a foot you smell nothing?

[birdcharm]

It seems to have something to do with the scent for the most part.  Some scents will linger longer because they have been created in layers, with attention given to the middle and bottom notes, rather than just a top note that you pick up on right away, but doesn't seem to accumulate in the atmosphere.  Some fragrance oils out there do not incorporate several aromas blended together to make a deep, multi-layered fragrance, they are simple formulas that smell fairly basic.  I hardly have any oils that I can use out of the bottle without adding something to it to make it fuller and more vibrant.

[NightLight]

Also many of the fragrance oils are geared towards soapers not candle makers. You do have to search out the gems for candles.

Some are hot and others are not!

 

[TallTayl]

Fragrances are made of endless combinations of aroma chemicals (even essential oils). They all have different temp ranges where they shine. Some need a stringer flame temp and more air current to boost them higher into the air. Some are light as a feather and disperse well. Some fall to lower levels like the floor or down stair wells and seem to not throw when standing near it above the lit candle. 
 

also the solvents used to make the bottled dilution behave differently in various waxes. old favorite phthalates worked wonders even with imperfect fragrances in harder to use waxes like soy. Now labs can choose between so many different diluents, like dioctyl adipate, isopropyl myristate and others. None seem to work as well as phthalates once did. 
 

Veg waxes tend toward the acidic. Newer Soy related blended waxes seem to have a narrower selection of “awesome” throwers than old fashioned waxes. You have to tweak to find the sweet spot, often swapping around wick series to hit the range of temp and rate of consumption balance. 
 

finally, the concentrations within each bottle vary. all retail bottles smell so weak compared to the bottles we used to get when I started so many moons ago. I have to buy more concentrated fragrance direct from a lab to get what I like.