Based on everything I've learned with every oil, redistilling twice degrades therapeutic value of the oil. The oils with the lowest voltage usually have double distilled. You can't tell so much by smell because the good essential oil is mixed in with the bad.
I have asked every company if they redistill and I have never came across any copany that has said yes. Why is there so much talk about it if no one does it? Well, you can't lie to someone who does their own testes. I know what redistilled oil smells like. There is a subtle difference that when you smell both types, then you easily know.
Note: Distilling oils for too long, or too high of a temperature can be just as bad as double distilling. Oil that has been only first distilled is generally higher priced oil. When I see an oil too cheap, I usually find that the therapeutic qualities have downgraded by something not good on part of the distiller or some other reason. Maybe its been out on the shelf too long.
The most sought after and the most expensive oils on the market are the oils that are extracted during the first part of the distillation process. This is why some of the non commercialized oils are so limited. This "initial distillation" is the most potent. I know some dirty secrets where some companies skim this off for themselves and sell it to the rich people who will pay a premium. I have talked to companies a bout this and the most reputable companies will not take this out. If you wonder why some oils have different smells this can be one of the reasons.
What you will never see anywhere is information about essential oil extraction methods and how it impacts quality and how it will produce an oil that is either better suited for therapeutic purposes, fragrance purposes, or functional (cleaning, disinfecting, polishing etc.)
Visiting one of the largest oil distilleries last year (sells to 2 of the largest essential Oil companies) I was there all day observing and learning about their processing of raw material that comes in all the way to the end product as fragrance, therapeutic, and functional.
Ok well to be honest I kind of came in half way through the process as it can take 12-20 hours to go from start to finish. So after another six hours passed the density of the oil they were distilling was about between 0.905-0.910 which was then poured and collected. That material was known as Grade 3B which would be sold to a fragrance manufacturer for adding scent to consumer products. There was some oil still left and I asked what it would be used for. This 4B grade would be sold to one of the largest janitorial supply company who makes an Eco friendly Green Cleaning line.
So generally speaking as the oil is distilled longer, or with more heat or pressure, the density of the oil changes. The most potent oil has a different density than oil that was distilled the longest that comes out in the final stage of distillation. Depending on the constituents and other properties of the raw oil material and what is the end purpose for production, an oil may require more pressure or less, or 1 distillation through or 3 cycles total usually in fractioned stages. They might only redistill the bottom of the barrel but not the oil at the top of the barrel. Some of the continuants desirable for perfumes for a certain oil have to be extracted after one distillation round and medium pressure. While some Lemon Oil constituents for cleaning are made more potent in their disinfecting power after twice as much pressure is applied.
This distillation plant had a method and process for every oil for every end point consumer usage. That day they were working on 2 non Organic Low pressure productions and lower grade of oils that would be sold in a huge convenience chain across the country.
As the Operations Manager explained it they are kind of like a one stop shop for the various essential oil companies. Anyone really can come to them and if they meet the minimum production quantities can have their raw plant material turned into whatever grade of product they want. It’s kind of like ordering from a menu of options. On the consumer end most people don’t know that many times there are two different brands of oils sitting on the retail shelf and they actually are coming out of the same manufacturing distillation facility. One company may have desired better profit margins and selected certain options that got them where they wanted to be financially and the other company may have selected different criteria.
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