This may be one of those standard newbie questions, but I was wondering which of the many chemicals in a perfumeís formulation tend to lend longevity to a scent ?
Certainly longevity is a valued quality in a scent, and itís likely that perfumers realize this as well. But I continue to read about fragrances, even those from high quality and respected lines which, by general consensus, simply donít last very long.
Is it that only certain primary fragrance components ( the ones selected mostly because they ďsmell goodĒ) also bring with them the quality of persistence, or is it that certain other aromachemicals designed specifically for their ability to enhance longevity ( assuming that there are components designed and included primarily for this purpose) have a tendency to sabotage certain specific desired fragrance outcomes, and thus must be excluded from certain formulations ?
Probably not a question with a simple answer, but it does seem that some formulations (not limited to the all-natural ones) apparently find it necessary, for whatever reason, to limit or exclude components that enhance longevity.
Any ideas as to what those components might be, and why some formulations apparently donít or canít contain them ?
In a first approximation volatility is inversely proportional to molecular weight. A rule of thumb is that adding one carbon increases durability by a factor of two.
Second, there is the fact that one the ethanol has evaporated, the different components of a perfume act as solvents for each other, and as the mixture evaporates this solvent effect changes continuously.
The high-molecular weight odorants like musks, etc act both as fragrance materials and as low-volatility solvents or fixatives.
It is possible to have odorless fixatives, e.g. farnesol and phytol. Intrinsically durable materials can also be ones where the curve of odor intensity vs concentration is very flat, so that 10% smells much like, say, 1%.
That means you can put a lot in without overwhelming the perfume, and the effect of the material will change little during evaporation.
Thanks for you kind reply. I suspect that others here have also wondered about the chemical mechanics ( if you will ) of the drydown process.
Which means that certain fragrance components, as stand-alones, have intrinsic volatile lifetimes based on their inherent molecular weight alone.In a first approximation volatility is inversely proportional to molecular weight. A rule of thumb is that adding one carbon increases durability by a factor of two.
OK, I think I follow you. After the alcohol has evaporated, the initial components are then left to interact among each other in a manner that can constantly change as each componant, and the varying compounds they interactively produce, gas off in ever-varying ratios based on the differing molecular weights of those compounds. Which could explain why people often report brief periods of less-than-consistant odor evolution as the hours progress.Second, there is the fact that one the ethanol has evaporated, the different components of a perfume act as solvents for each other, and as the mixture evaporates this solvent effect changes continuously.
Which would mean that they contribute to the longevity of lower-weight fragrance componants by combining with them to produce products of a higher molecular weight which off-gas at a rate slower than what those materials might do if left to stand alone.The high-molecular weight odorants like musks, etc act both as fragrance materials and as low-volatility solvents or fixatives.
I see. So one of the values of such fixatives is that they can be heaped into the formulation while apparently contributing relatively small fragrance changes of their own.Intrinsically durable materials can also be ones where the curve of odor intensity vs concentration is very flat, so that 10% smells much like, say, 1%.
This is all well and good, but I'm still not sure if it answers my question. If fixatives are available which are orderless themselves, or can be added in high proportion to the intrinsic odors they do contribute, why do we still have perfumes of limited longevity from houses which would seem otherwise able to fork over the cash for such fixatives ?That means you can put a lot in without overwhelming the perfume, and the effect of the material will change little during evaporation....It is possible to have odorless fixatives, e.g. farnesol and phytol...
While they may be orderless themselves, is it that the compounds they produce through their interactions with the intentionally fragrant components result in higher-weight compounds who's odors, while now more persistent, are at the same time incompatible with the fragrance profiles that the perfumer hopes to achieve ?
Perhaps it's that certain wanted odor profiles simply depend on final compounds of a necessarily low molecular weight in order to produce the smells the maker hopes to produce ? Beyond the initial top notes, I mean.
I guess I just have this sense that something beyond mere economics or simple dilution is at play when we come across fragrances with seemingly puzzling longevity issues.
Sorry, I suspect you can tell I was one of those kids who certain teachers hated when I was in school....
In a nutshell I think a perfumer is composing not one fragrance, but several in succession that form as the materials evaporate, and the artistic interest and coherence of each of the stages has to be optimised for the whole thing to work. A short-lived fragrance, unless it is specifically designed to be so, is usually an indication of lack of technical skill. Note btw that perfumery materials do not generally react with one another in the sense of forming and breaking covalent bonds. Their interactions are weak intermolecular forces, comparable in strength to thermal energy at body temperature.
Non chemist here . . .
As I understand it in 'the good old days' perfumers would build from the base up and it seems to me that a number of vintage or retro classics illustrate this, in that you are looking at a composition with three dimensions, so to speak. By the time you hit the final stretch there is still something there with substance, be it an earthy 'forest floor' or a warmer 'Guerlainade' style - amber / vanilla / tonka etc.
It seems to me that a lot contemporary stuff is way more front loaded - the spritz at the counter effect - and then shortly thereafter the illusion of the initial (often glorious) accord is sustained by some seriously strong 'quick fix' synthetics in the form of the dreaded 'woody amber' or, increasingly, relentless vanilla and/or a hodge podge of musks.
I realise this is a simplistic take on it but, like the use of samplers and loops in music, these ever increasing and readily available aroma-chemicals with a half life resembling plutonium are within easy reach so the art of calibrating quality fixatives within a composition is becoming a lost art.
I think it's just laziness, really, and good old fashioned greed - why bother if most people don't know or don't care? I find I'm more likely to walk away from something with potential up-front if it becomes clear to me that it lasts too long. I could cite examples but you get the idea.
Actually the "good" old greed is the greatest issue. A fine regulation of all the components requires time and experience. Both costing much more than any chemical, even the precious ones
Sebastiano - Organic Chemist
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So in some cases it may indeed be, as Otocione says, and as one often hears in knowledgeable reviews, simply a matter of the limited number of man-hours that are budgeted to the particular endeavor, rather than any inherent impossibilities in achieving certain outcomes.
I'm getting the sense that the explanation for shortcomings in longevity are more complex than an outfit simply being too cheap to throw in the needed fixatives. Perhaps I'm wrong, and fixatives are indeed one of the more expensive ingredients, and a reasonable place to skimp. But it comes to overall expense, I'm beginning to get the sense that the number of man-hours involved in reaching a desired end-point makes for the most expensive ingredient of all.
Last edited by Birdboy48; 17th September 2011 at 04:49 PM.
Well from what I have gathered on this site, it seems "civet" is an ingredient that lasts a long time but then people complain that it smell like cat piss but others don't smell the cat piss. So I think maybe something that helps the perfume last a long time might not be appealing to the mass public.
It is never the situation when a perfumer thinks "Well I've created this Perfume, now I'll add some fixative to it'. The longevity of a fragrance is part of the fragrance, it is not a separate issue. Base note materials, those with the lowest volatility will, in some cases, also act as fixatives for the whole fragrance, as has been explained above. However, not all Base materials act in this way. It is part of the skill of the Perfumer, with his knowledge of the behaviour of Perfumery materials, to be able to control the longevity of a particular fragrance. In my working life, I often was told by the Account Manager that a particular customer "just loves the fragrance, but wants it to last longer". And even, in the case of some Air Fresheners, "can you make it evaporate faster".
New Perfumes seem to concentrate on a strong opening, but show little concern with the dry down. Customers want an instant hit, and the manufacturers give it to them, without bothering with the rest. Most Perfumers have to work to a schedule , andto the demands of customers and the companies they work for.