Making Medicine, Part 4 of 5: Equipment for Pressing and Filtering Tinctures

This is the fourth post in a series in which I am using the process of wild harvesting and making a fresh herb tincture of blue vervain (Verbena hastata) as an example to explain in detail the process of making herbal tinctures.

Part 1 of this series was posted on July 9th, Part 2 on July 15th, and Part 3 on August 22nd of 2012. After that I got busy and forgot about it, except periodically when someone reminded me about it. The truth is, every time it came up I thought about having to find and drag some old equipment out of storage and set up and take a bunch of photos and I put it off and forgot about it. Well, here is the next installment at last!

This was supposed to be the last post in this series, but it keeps growing! Every time I've worked on it I've realized that there is so much info to cover I keep extending it. However, I am confident that the fifth part will be the last.Taken as a whole, this series is one of the three most viewed offerings that I have posted so far. My apologies to those of you who have been patiently waiting for the conclusion.

In the first three posts we got up to the point where we have prepared the maceration of fresh blue vervain herb and it is being stored in the dark for a minimum of three months. As I stated previously, we don't want to press the maceration until we actually need it because the greatest amount of degradation of the active constituents occurs during the pressing process and afterwards. Once we know that we will be needing the tincture of a particular herb that we are macerating, starting about a week before we press it, it's a good idea to shake it vigorously once per day for about 30-60 seconds and then again immediately before we press it. This helps break up the plant material further now that it is much softer from having soaked for awhile and to get some more of the constituents out of the herb and into solution.

In order to prepare our tincture, the final step requires that the maceration be pressed and filtered. Let's begin by discussing pressing. The purpose of pressing the tincture is to squeeze as much liquid as possible out of the macerating plant material, which is technically called the marc. The more intensely we are able to press the plant material, not only do we get more tincture as an end result, we also get a somewhat stronger tincture because the fluid that is deep in the herb will tend to contain the highest concentration of its constituents. There are different kinds of pressing equipment that work to varying degrees. Unfortunately, as we might expect, the better the press the more expensive it is going to be. This means that we need to strike a balance between wanting to use the best equipment that will produce the largest volume and most potent tincture with the cost. In the long run, if we are serious about making tinctures it is preferable to use the best equipment that we can afford.

There are essentially four ways to press a tincture. Many books recommend the simplest method which is to pour the maceration through a few layers of cheese cloth and then wring out as much liquid as possible by hand. This process is so inefficient that, personally, I consider it a waste of time (and herbs). The simplest and most inexpensive method for pressing your maceration is to use a potato ricer. However, the standard cylinder type ricers are not recommended. They are not strong enough for pressing herbs and will break pretty quick. Although they are more expensive, the best ricer is what is usually marketed as a "professional" potato ricer. These have a triangular shape (see photo) and the part that takes most of the pressure is much stronger. Not only will they allow you to use more pressure, they will last much longer.

The standard cylinder ricer (left) is not strong enough for the kind of pressure necessary to press tinctures. The older professional ricer (middle) demonstrates what happens after many years of use. Note how the point with the wire is wrapped around it is bent out of shape. This is the point that takes the stress from all of the pressure. Wrapping wire around this point will increase the life of the ricer by helping to prevent the parts attached to the handle from slipping over the corners of the bar. The newer model with the more solid handle (right) is better because it isn't as hard on our hands when applying pressure. I used to have to use a towel wrapped around the handle of the old one. This isn't necessary with the design of the newer one.

The next best press is the screw press. There are many types available. They are usually used for pressing grapes to make wine or apples for cider. Wooden presses do not work for tinctures. Only stainless steel presses will do. Most of the better ones are made in Italy. However, there are some flaws in the design of many models that I will address. The more of these features that a press has, the better the quality.

Firstly, it is important that the design has an inner straining cylinder with holes that will contain the herb material while allowing the fluid to pass through, and a slightly larger solid outer cylinder with a hole and spout that allows the fluid to flow out. Ideally, the hole should be flush with the bottom of the container. Although most designs don't have it, it is best if the part of the press that the container sits on has some kind of brace that the spout fits into to hold it in position. Otherwise, when the pressure gets fairly high while we are pressing the tincture, the container and the position of the spout will spin. Another important point is that it is not recommended to just let the tincture flow out of the spout into a beaker or other container. It is best to attach a hose so that we can better direct the flow. Most presses don't come with a hose and it is necessary to purchase one. It's important that it fit snugly on the spout. If it isn't tight enough we can add a hose clamp. The material that the hose is made of is also important. We don't want to use PVC or other materials that will leach toxic chemicals into our tincture. A low-density polyethylene hose (LDPE) is probably the only material that is relatively non-toxic.

Another aspect of the design of a screw press that is important is how the metal disc that presses the herb material is attached to the screw on which it is mounted. Because of the tight fit between the disc and the inner cylinder, many companies do not weld the disc to the screw, but attach it loosely so that it can move. This makes it less likely to get jammed in the cylinder during the pressing process if it is slightly misaligned. The problem with this design is that, as the pressure on the herb increases, some of the tincture will seep up through the space between the disc and the screw and come in contact with the screw. This will allow some of the lubricant on the screw, which will be some kind of rancid oil that also contains fine metal dust from friction between the metal parts, to get into our tincture. This can even be a problem with presses for which the disc is attached to the screw because when the herb material is under a relatively high pressure the tincture will often flow out faster than it can seep through the holes in the inner cylinder. When this happens it will flow through the space between the disc and cylinder and over the top of the disc. Once more it could potentially come in contact with the screw unless the part of the disc that is mounted to the screw is relatively deep so that the level of tincture on top of the disc isn't higher than the point at which the disc is attached to the screw. Unfortunately, most screw presses have one or both of these flaws in their design. There is, however, a way around it and that is to insert a wooden disc between the metal disc and the herb. To do this it will be necessary to cut a round disc that fits fairly snugly into the inner cylinder of the press. It should be at least 2 cm (3/4 inch) thick and made from a relatively hard wood with a tight grain. I have found the best choices of wood to be (in descending order) sugar (hard) maple (Acer saccharum), white ash (Fraxinus americana) or American beech (Fagus grandifolia). There are even harder woods from tropical trees, but as these are usually harvested in an unsustainable manner that has a negative impact on tropical rain forests, I don't recommend them.

The purpose of the wooden disc is not only to prevent the metal disc (and the end of the screw if it is loosely attached) from coming in contact with our herb material, but also to help prevent the tincture from coming in contact with the screw by flowing up over the outer edge of the metal disc. The thickness of the wooden disk allows the tincture extra space where it can flow unimpeded through some additional holes in the inner cylinder. A 2 cm disc will usually be adequate, but up to twice that thickness might be a good idea for an extra margin of safety. For presses for which the metal disc is loosely attached to the screw, if we use a wooden disc between the metal disc and the herb material it is necessary to always position it so that the same side of the wooden disc is facing upwards. This is because inevitably the grease and metal dust from the screw will come in contact with the wooden disc and we don't want that side of the disc coming in contact with our herbs or tincture.

Another thing to look for in a screw press is the design of the frame that holds the screw. With most presses the part that holds the screw is attached to the base at two points. If we don't use the press too much this isn't an issue. However, if we use it a lot and really crank it to squeeze as much tincture out of our herbs as possible, I have found that this design isn't strong enough. Eventually it becomes loose at the points where it attaches to the base. The best designs are those where the part that holds the screw attaches to the base at three points. This is far more stable and more durable in the long run.

This older screw press is the standard design. You can see that the upper part of the frame that holds the screw is tilted from long-term use. The handles aren't long enough to easily apply sufficient torque for pressing tinctures. The metal disc isn't securely fastened to the screw so that it can rotate and tilt slightly, but it leaves enough space to allow tincture to flow up between the screw and the disc and come in contact with the grease on the screw. We eventually welded the disc to the screw with one of these, but due to the thinness of the attachment point, tincture was still able to flow around the edges and up over the top of disc and come in contact with the screw. Adding a wooden disc between the metal disc and the herbs was necessary to prevent this.

There are two more aspects of the design of a screw press that are important. The first relates to the handle that we use to turn the screw and put pressure on the herbs. Most of these presses have handles that are too short. The longer the handle the better. Not only is it easier to grip, but it allows us to put more torque on the screw and therefore more pressure on the herbs. The last issue is that it is best if the inner cylinder has a bottom. Some designs have inner cylinders without a full bottom.

In summary, I only recommend stainless steel screw presses with a two cylinder design and a spout on the outer cylinder. It is best to get one that has a capacity of 1-2 litres (approximately 1-2 quarts). In terms of the design issues I mentioned, the first (metal disc attached to screw with a deep attachment point) is the most important, however, it can be compensated for by using a wooden disc between the metal disc and the herbs. The second (three attachment points) is slightly less important, but it becomes more important the more we use the press. The third (long handles) is even less important, but this little detail can make a big difference in terms of ease and efficiency of use. The fourth (inner cylinder has a bottom) isn't that important, but it does make the press a bit easier to work with.

This is the best designed screw press that I have come across. It has three attachment points for greater stability, strength and durability; larger handles making it easier to turn the screw and apply more torque; a brace in the base that holds the spout in position; and a superior design for the disc attachment (see below). Although parts of the frame are made of aluminum, all of the parts that come in contact with the tincture and herbs are stainless steel. It even has holes in the feet so that it can be secured to a counter or piece of wood for greater stability. However, it is important to be able to tilt the press forward to drain the last bit of tincture out of the cylinder. It could be attached to a piece of wood as long as it is not too large, the front is straight, and doesn't extend too far beyond the feet so that it will still be easy to tilt the press forward. The only disadvantage of this design is that the inner cylinder doesn't have a bottom (see the photo of inner cylinders in the discussion of hydraulic presses below). However, this is only a minor issue; the least important of the various design issues that I have discussed.

Here is a closer look at the disc attachment. It allows the disc to spin so that it is less likely to get jammed in the inner cylinder. It also is fairly deep at the attachment point so that any tincture that flows over the surface of the disc will not come in contact with the grease on the screw. If we press the herbs relatively slowly towards the end, the amount of tincture that seeps up between the outer edge of the disc and the inner cylinder is minimal.

There is one modification to the screw press that I highly recommend. I have found that it is best if the herb material doesn't sit in a pool of tincture. This is because when we apply pressure, after a bit of time the herb material seems to settle a bit which causes a slight reduction in the pressure. When that happens, if the herbs are sitting in the tincture they will reabsorb some of it. Therefore it is best if the tincture is able to efficiently flow away from the herbs as soon as it is pressed out. This is one of the reasons why a press design with a spout is absolutely essential. However, because the bottom of the cylinder is horizontal, the last bit of tincture doesn't flow out very fast. To avoid the herb material sitting in a pool of tincture, what I have found works best is to use a wooden disc as described above. This disc is placed inside the outer cylinder before we insert the inner cylinder so that the inner cylinder is resting on the disc and elevated above the bottom of the outer cylinder.

The third major type of press is the hydraulic press. The best hydraulic presses are the electric ones because they can apply the most pressure. However, these tend to have three limitations. Firstly, they tend to be designed for a larger capacity and are not suitable for small quantities of tincture. Secondly, many designs don't have an outer cylinder. This might be OK for pressing grapes, but for many herbs the tincture will spray out in a way that needs to be contained by an outer cylinder. The third limitation of electric hydraulic presses is that they are extremely expensive. I would only recommend an electric hydraulic press for the production of tinctures on a very large scale requiring the pressing of 4-5 litres or more at a time. Even for an herbalist who has a busy practice and produces all of their own tinctures this is not likely to be economical.

As an alternative, there are a number of designs out there that use a manual hydraulic mechanism. Basically they attach an hydraulic bottle jack (which is typically used as a car jack) to some kind of frame. I have seen a number of designs and most of them are examples of enthusiasm more than efficiency. The typical design is to use an hydraulic bottle jack to squeeze herbs between two stainless steel bowls and then pour off the tincture by tilting the "press" (no holes, no spout). I don't recommend any of these. There is only one that I have come across that I recommend and it is the press that I use myself. Although it's not perfect, it is the best press I've ever worked with. I am always experimenting with different kinds of equipment for making tinctures. I have to say that of all of the equipment that I have acquired, the two most important things in terms of efficiency are my mezzaluna (see Part 2) and my hydraulic press.

This is the best manual hydraulic press that I have come across so far. It works very well but has two design flaws. Firstly, it is too top heavy and awkward to work with. I have a lot of experience working with presses and I don't find it too difficult to use, but most of my students have difficulty working with it on their own and need to work in pairs when using this press. The second design flaw is that there are too few holes in the inner cylinder (see below).

 Note the significant difference in the number of holes between the inner cylinder of the hydraulic press (left) and the screw press (right). Even if it had additional columns of holes in between the existing columns with the spacing of the holes half way between the existing holes it would be a significant improvement. I will probably drill them myself at some point. The cylinder on the left includes a cotton filter which is flared at the top so that it easily folds over the top edge when the maceration is being poured in. The wooden disc (centre) is positioned between the outer and inner cylinders so that the inner cylinder sits on top of it. The filter and the disc are both very stained from the tannins in herbs. Note that the inner cylinder of the screw press doesn't have a complete bottom. It is the only design flaw with that particular press, and a minor one at that.

There is one more trick that will significantly improve the efficiency of pressing and filtering. It is best to use a filter inside the press. This allows the maceration to be filtered under pressure. It eliminates the need for a separate filtration step and significantly decreases the amount of time of the whole pressing and filtering process. This is very important, not only in terms of saving time, but because the less time that elapses between when we open the jars containing our maceration and when we seal the finished tincture in a bottle, the less degradation of the active constituents that will occur. That means a better quality tincture. It is best to custom make filters that fit inside the inner cylinder. They should be a little taller than the cylinder and flared at the top so that they can easily be folded over the top of the cylinder when we pour our maceration into the press. Otherwise the filter will collapse as we pour the maceration into it. The filter should be made out of unbleached cotton or some other natural fibre, preferably certified organic. Use a coarse weave because it will filter easier and we actually want the thicker sediments and latexes of the herbs in our tincture. Before making the filters, it is important to wash the fabric several times with natural detergent because fabrics these days tend to be coated in all kinds of toxic chemicals (see Toxic Threads for more information). It is best to add some vinegar to the water as well.

If we don't use a filter in the press, it is necessary to filter the tincture after pressing it. In this case we allow gravity to filter it through a cotton filter placed inside a funnel over a beaker or other receiving container. We position the hose to allow the tincture to flow into the filter from the press. It is necessary to press the maceration more slowly when using this method so we don't overflow the filter.

There are other designs of equipment that can be used for pressing tinctures. Although I would love to, unfortunately it isn't possible for me to purchase and try them all. Most of the presses I have seen online aren't very good, but I suspect there are a few out there that are worth checking out.

This ends my discussion of pressing and filtering equipment. In Part 5, the final post in this series, I will cover the actual process of pressing and filtering our maceration.