Fragrance question

[imanimani36912]

Hello All,

I have a burning question that I can't find the answer to anywhere else so I'm asking here. I've noticed that melt and pour soap retains scent and color better than cold process soap in most cases.

Why?

It can't be because of heat since you can make soap at room temperature and melt and pour melts at 120 degrees.

Is it due to an extra ingredient in melt and pour? If so, which ingredient?

I don't think it's pH since the pH of melt and pour and the pH of cold process soap are very close, if not the same in some cases.

I would greatly appreciate any responses .

 

[Megan]

It's because it doesn't go through the saponification process. Meaning, the lye actively breaks down some of the fragrance. There is no free lye in MP.

Hot process is similar in terms of how much scent you use to MP from what I've heard.

Edit: I'm also from NEO!

 

[yolk]

I don't know about color retention in MP soap, but I think scent retention has something to do with the propylene glycol in the bases. That's my guess from the little I know.

 

[LilianNoir]

A few things can effect the fragrance retention, and the environment of cold process batter is quite different from melt and pour. By the END of saponification and curing the result is the same but consider:
1. Temp. Melt and pour is melted and worked with around 120-130F. Cold process soap can start at that temperature (or can start lower) and heats up as it saponifies. Cold process batter can reach up to 180F (possibly higher if it overheats).
Consider also that, depending on what you're doing with it, the melt and pour base doesn't stay at the 120F range for very long. Cold process batter will be warm for hours through saponification.
Aroma chemicals(that make up fragrance oil) can be quite sensitive, so the prolonged heat of saponification can certainly make a difference.

2. pH. Melt and pour is a finished soap and has a pH similar to finished cold process soap, 8-9, I've read the cold process is between 9-10. But raw cold process batter is around 12 on the pH scale.
That doesn't seem like a big difference, but remember the pH scale is logarithmic, not linear, and that difference is certainly enough to effect more sensitive aroma chemical molecules.

3. Saponification. I'm not sure if the oils in fragrance oils are saponifiable, but considering how many components are in fragrance(both synthetic and natural) it's not impossible that some of the fragrance may saponify. Most likely though it's a combination of heat and pH.

 

[LilianNoir]

Re: color. I haven't noticed a difference with micas and pigments. Liquid colors may behave differently due to the additional ingredients(such as propylene glycol) in some melt and pour bases.