Originally By Tony Ackland
Essential OilsWal writes ...
My understanding is that if you want the maximum yield, pot distillation is the method to use. Yields are below 5% therefore you need lots of material if you want pure oil and not just flavoring.
For % yield from herbs and spices see http://www.switcheroo.com/Extracts.html
For historical (Medieval) recipes see http://www.gallowglass.org/jadwiga/herbs/oil&water.html (and then select oils&water.html from the index).
Type "essential oils" in a search engine.
I have no personal experience in essential oil distilling except where I have distilled crushed aniseed, orange peel and lemon peel as part of the wash in a reflux still producing 70%abv, to produce raki and triple-sec. Tony Ackland (see Flavoring) uses a small pot still to produce a gin essence from botanicals specific for gin. Commercial gin distillers either macerate the botanicals in 45% alcohol by vol. and then redistill or pass the alcohol vapor through a suspended wire basket in (I suppose) the second distillation stage.
This is what the instructions for an 'Essential Oil Kit Distiller' say:
Method 1. Water dissolvable oils.
Soak the material containing the oils to be extracted in water for 24 to 48 hours. Strain off the solids leaving just the liquid behind. Add this liquid to the still and bring to the boil. Make sure there is enough water flowing through the condenser to condense any steam which comes out of the condenser. Collect the distillate in 100 ml quantities. Test each 100 ml batch before combining to ensure quality is acceptable. As the condensate is driven off the nature of the oils will vary.
Method 2. Steam dissolvable oils.
Fill the still with 5 litres of water. Suspend the material containing the oils in a wire basket above the level of the water. Bring the still to the boil and collect the condensate which is produced. As the steam passes through the material, it will pick up the oils and carry them through with the condensate. Make sure there is enough water flowing through the condenser to condense any steam which comes out of the condenser.
Method 3. Alcohol dissolvable oils.
Soak the material containing the oils to be extracted in 50% by volume alcohol for 24 to 48 hours. Strain off the solids leaving just the liquid behind. Add this liquid to the still and bring to the boil Make sure there is enough water flowing through the condenser to condense any steam which comes out of the condenser, Collect the distillate in 100 ml quantities. Test each 100 ml batch before combining to ensure quality is acceptable. As the condensate is driven off the nature of the oils will vary."
As the vapor consists of alcohol and water my view is that Method 3 would suit all herbs and spices. You would need to check this.
Scrounge adds ...
I've found that rather than messying around with baskets to hold herbs about the steam it's perfectly possible to pack your still densely with the herb in question, add about 1/4 that volume water and distill slowly - the stuff that comes out the other end is a cloudy mixture of water and oils that soon settles out.
There are very few oils that occur in decent quantities to be worth trying at home - Lavender, rosemary, mint and citrus peel all work well. Chamomile can be done if you use an alcohol maceration and keep adding replacing the chamomile, what you end up with is very pleasant smelling spirit suitable for addition to bath water or skin application. Incidentaly, chamomile comes off blue - just in case you worry what's happened to the still.
They typically have a small lower chamber for the water, then a container that holds coffee grounds (the bottom is a perforated plate, keeping the grounds off of the water). Above this is a little spout that the steam (after going through the coffee) passes through, which empties out the espresso into the upper chamber. Look at what's available on the shelf at the store. Don't buy a coffee percolator- the thing I'm talking about allows only steam to pass through the coffee grounds (steam distilling the coffee). I bought one in the U.S.A. for $10 (it's a small 3 cup model), made of aluminum, and works great for steam distilling rosemary and lavender oil.
When I pour the steam distilled product out of where the coffee normally is into a glass cup, these oils show up as an oil on water layer- to prevent them from going moldy, I add some petroleum ether (mineral spirits), shake in a sealed jar, then pour off the top (ether) layer and evaporate it, leaving behind the essential oil. I haven't tried it with cirtus, juniper, nutmeg, or anything else, but it should work for these plants/flowers.
By the way- use distilled water for the best results.
Using OilsWal writes ..
A useful site for essential oil yield is: http://www.benzalco.com/ While there check out their pot stills. For details of herbs see: http://www.botanical.com.
Recipes indicate that 7 drops of essential oil per litre of spirit is the minimum requirement. About 1/2tsp. of essential oil/litre of alcohol (40%abv) seems to be the optimum amount. To be safe, begin by using 1/8 tsp., then add more drops of oil until you are satisfied with the flavor. With anise oil you should not go below proof as the anise oil turns white in water. Extracts are essential oils diluted in alcohol and usually 4 units of extract is equivalent to 1 unit of essential oil. The S.G. of oil is about 0.8kg/l.
Alcoholic strength effects aroma. The trigger point for volatile citric aromas would appear to be around 40%. Dilute to below that strength and you will kill them. 45% abv appears to be ideal for gin. The flavoring ingredients are all natural and are referred to as 'botanicals'. All gins include juniper and coriander. Gordon's also uses ginger, cassia oil and nutmeg. Beefeater uses bitter orange peel, angelica root and seed. Plymouth's 7 botanicals include sweet orange peel, cardamon . Bombay Sapphire uses cubeb berries, cassia bark, grains of paradise, almonds, lemon peel, liquorice, orris root, angelica root. Typically a fine gin contains 6-10 botanicals. The combination of botanicals is important. Angelica root helps to hold in the volatile citric aromas. In most cases the botanicals are steeped in 45% alcohol.This is then redistilled to release the essential oils from the botanicals (less than 5% of the weight - you can therefore work out your yield). Only the middle run at about 80-85% is used.
More essential oil links from Wal ...