How Do Bubble Plates Work (Explained)

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If you are new to distillation, you may have heard of bubble plates. But, perhaps you are unsure what they are or how they work.

In this article, we will delve into what a bubble plate is, why it is used in distillation, the anatomy of a bubble plate, and the benefits of using it.

What are bubble plates?

Bubble plates are a component of a distillation column that helps create reflux inside a distillation column. The simplest way to think about it is every time you boil a liquid another distillation occurs, and the purity of the product goes up. Each bubble plate provides an area for vapor to condense and boil again, and thus another distillation occurs. The more plates you have the greater the purity of the final product.

The purpose of a bubble plate

The main objective of a bubble plate is to force vapor and liquid to interact with each other inside the still. The result of this interaction is that you will produce a vapor with a much higher proof than if you were using a traditional still.

This is because the bubble plates create more reflux inside the column. Essentially, what the bubble plates do is that they create multiple distillation cycles within a single run, which creates, as mentioned, a higher proof. 

A distillation column creates a phase change from vapor to liquid and then back to vapor again. This phase change may occur multiple times in a single run, or over several runs. The phase change will continue until the product reaches the condenser. A key component of this process is the bubble cap

In essence, the bubble plate strips the flavor from the final product as well as creates a higher proof. Ultimately, the bubble plate produces quick results of a higher average proof. 

Some professional distillers may add a dephlegmator to the still to create an even higher proof. 

The anatomy of a bubble plate

A bubble plate is a cylindrical plate or tray that comes in various sizes:

  • Two – Three inch plate – Small hobby size
  • Four – Six inch plate – Large hobby size/nano distillery
  • Eight Inch and up – Commercial size plate

The size of the plate will match the size of the column. A four inch plate will sit in a four inch column. A six inch plate will sit in a six inch column, and so forth. The plate has a specific number of bubble caps and a specific number of downcomer (downsprouts). The bubble plates can be customized as well to fit the individual operating needs of the user. For example, on a four inch plate you may have six holes (vents). Five of the holes are for bubble caps and one hole will be for a downcomer. 

The bubble caps and downcomers are essentially the same thing. In fact, the are often the same part used to save on manufacturing two different components. The bubble caps face upwards and sit on the surface of the bubble plate while the downcomer faces downwards (the other direction) and sits at the bottom of the bubble plate. The downcomer increases production speed by pushing more heat toward the kettle. 

The purpose of the valve tray or trap is to force the liquid and gas to mix.

The bubble cap

The bubble cap is made up of three components. The bubble cap itself (riser), the top (the cap), and a fixture (screw) to fasten the bubble cap. The riser is slotted into the tray and the cap fits over the riser. The set is then fastened with a screw. The cap is a metal fixture that has slots around the bottom or edges of the cap. 

An important side note is that the riser has small holes at the top that allow the vapor to escape into the cap that pushes the vapor back down again under the liquid.

The cap is essentially a one-way valve that allows vapor to move through the cap but prevents liquid from moving back down again. 

How do bubble plates work?

This is an overview and a glance at exactly how bubble plates work.

Vapor moves up the column and into the riser. The riser, as mentioned before, has holes at the top which allow the vapor to escape into the cap that covers the riser. The cap then forces the liquid back down and under the liquid that sits on top of the plate. This process creates bubbles and this is the forced interaction between the vapor and the liquid.

In addition, and as previously mentioned, this means that the bubble cap is a valve that works in a one-way direction. The vapor is allowed to move up in the still but the liquid is prevented from moving back down again. 

The downcomer works on the same principle but in the opposite direction. The downcomer also works as a one-way valve. The difference is that vapor is prevented from coming up and liquid is sent back down the column again. In the case of the riser, the holes are now situated at the bottom of the riser as opposed to being at the top of the riser in the bubble cap.

When liquid moves over the downcomer, gravity pulls the liquid back down, and it is released through the holes at the bottom of the riser. The cup that sits over the riser of the downcomer catches the liquid and acts as a small reservoir. As this little reservoir (the cap) of liquid fills up, liquid spills out of the cap and onto the plate at the bottom, or, essentially, back into the pot. 

The cup, filled with liquid, then prevents the vapor from moving up the column again. The height of the downcomer, sitting at the top of the bubble plate, determines the height of the liquid.

In essence, a bubble plate is made up of two one-way valves. One allows vapor to move through the riser and is forced by the cap to move down and under the level of the liquid, while the other valve allows the liquid to drop down into the pot below as soon as it reaches over a specific height. 

Consideration should be given in order to prevent flooding of the plate. 

How much power can different size bubble plates handle?

The following table highlights the plate size power rating.

2″ Bubble PlateUp to 3 kilowatts
3″ Bubble PlateUp to 4.5 kilowatts
4″ Bubble PlateUp to 8 kilowatts
6″ Bubble PlateBetween 9 and 11 kilowatts
8″ Bubble PlateUp to 30 killowats

While there are also 10″ and 12″ bubble plates, we have focused on those used in home distillation.

Bubble plate size and take-off speed

The following chart highlights the bubble plate size and take off speed. However, these speeds will differ greatly by pot size, wattage ability of the still, wash/mash, and heads, hearts, and tails, as well as the type of spirit being produced.

2″ Bubble Plate1.8 – 2 lph
3″ Bubble Plate3 – 4 lph
4″ Bubble PlateUp to 6 lph

How many bubble plates do you need?

The following is an indication of the number of bubble plates required to make each of the following spirits.

To make whiskey or rum

This will depend as there are several different types of whiskey and rum which may each be distilled to varying percentages. In addition, each of these types of whiskey and rum will be distilled to varying levels of proof.

Most home distillers may agree that if you run molasses Rum you may want to use four bubble plates. In addition, when it comes to whiskey, you may run two, four, or even five bubble plates. It will depend on the proof and flavor that you aim to achieve.

To make gin:

You may require a few as zero or up to six bubble plates in order to produce gin.

Obviously, the purity of the alcohol will increase by adding bubble plates and that will also trip flavor from the gin. Therefore, most gin distilleries don’t use any plates, or at least run their still with the plates ‘open’.

To make vodka

When distilling vodka, you will need six bubble plates minimum. In fact, to make ‘pure’ ethanol it’s widely accepted you’ll need a minimum of 14 plates. Thats a big still!!

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