Packed distillation columns are filled or "packed" with a material that allows rising vapors to contact with descending condensate as to promote vapor-liquid contact in separating the components of liquid mixtures to the desired purity. The more vapor liquid contact the better the separation thus higher ABV and quality. This is called natural reflux in the moonshine fraternity although not the correct termination and called fractional distillation. Columns are generally packed with a material containing a high surface area which also allows the vapour to pass through it.

Most used materials for this purpose are copper mesh rolled up (not copper pot scrubbers as majority of these are copper plated mild steel), Raschig rings, or glass distilling beads and the easiest way to increase the final ABV of your product while making it taste better. Copper off-cuts, pieces of copper pipe are also used in some cases but remember, the more contact are, the better.

As the gas-liquid contact in a packed column is continuous, unlike in a plate column which is stage wise, the liquid flows down in the column over a packing surface and the vapour moves up the column.

A packed fractionating is more efficient than an unpacked one because a packed column provides more surface area for the vapour to condense on. The more it condenses, the more efficient the separation of the liquids.

Leaving a column in full reflux will repeat this process all over the packing material, forcing the lighter alcohols to rise towards the top of the column and the heavier alcohols to fall down the column. This process of separating the wash into its alcohol fractions and collecting these off slowly is the process of fractional distillation thus the main purpose of this packing is to give a surface that falling liquid distillate can have contact with, which can then be further boiled by the rising distillate. Take note that this process will strip all flavors from your distillate, so the method is used for making neutrals.

Fractional distillation would be more efficient and successful if it encounters a large surface area and glass beads provide a large surface area. Also, glass beads function as “imaginary surfaces” on which the liquid can condense, re evaporate and condense again, thus distilling the wash again and again.

ubble plates are thus a type of packing and not a type of column as mentioned in the blog “types of columns.” In order retain flavour in your product minimal or no packing is used. This is the normally used when making whisky, rum or brandy. A proven setup to achieving great flavour retention whilst achieving high ABV is a column which utilises plates at various levels throughout as its ‘packing’. Each plate used provides a cleaner product, and a reasonable column height packed with copper mesh can have an equivalent result of 20 or more plates producing a high ABV output.

A lot of hype lately has been around flutes, and for good reason as the flutes are just scaled down versions of commercial plated columns. These types of distillation columns are renowned for both their flavour retention in the final product, as well as their collection speeds. 
 

Two types of plates are commonly used in hobby distiller’s plated columns, and the choice of which to use comes down to personal preference with almost identical results reported. The two common types are perforated plates and bubble caps. On a perforated plate, the plate consists of many small holes where vapour can rise through. On a bubble cap plate, the plate contains either one large, or several small caps with slots cut into them to allow vapour to escape which has travelled up a small tube through the plate and into the inside of the cap. 

This explanation will focus on the perforated plate now, however the theory of how they work is identical aside from how the vapour travels through liquid on the plate.

On initial boil up, the vapour begins to rise up the column, and as they reach each plate are able to flow through the perforated holes (or bubble caps) on each plate. Once the vapour reaches the top of the column and the reflux condenser, with adequate cooling, will condense the vapour and begin to fall back down the column. As the liquid is falling it will land on the first plate and instead of falling through the holes it is suspended by the vapour rising through the holes which in turn boils the liquid on the plate. The lighter alcohols will boil off this plate and continue up the column again as vapour towards the reflux condenser. 

his cycle continues and the depth of liquid on the plate (bath depth) increases to a point where it overflows into a tube going down to the next plate below. This tube is known as a downcomer. The downcomer places this liquid onto the next plate and this process continues until all plates are loaded with a bath of boiling liquid. As the system is left in full reflux (all vapour falling back down), the lighter alcohols work their way up through the plates towards the top, while the heavier alcohols and water work their way down lower in the column. At this point ethanol is boiling off each plate as vapour, while water remains on the plates and flows down the downcomers. 

Once the operator is happy that equilibrium has been reached, the coolant water flow to the reflux condenser is restricted, where a slight amount of the rising vapour will be light enough to make its way through the condenser without turning into liquid. This vapour will then reach the product condenser where it is collected. 

NOTE: As the cooling water is manipulated to control the output from the still it thus becomes a Cooling Management still.