Insulating helps keep equilibrium in the column which is the splitting the fractions of the heads hearts and tails. Insulating helps the temperature stay up as passive reflux from cold wind can harm or reduce equilibrium. :handgestures-thumbupleft:
From the different stills page below by Brendan
Liquid Management
As the name suggests, the output is determined by controlling the amount of the actual liquid distillate which is allowed to exit. This is usually achieved by use of a needle valve. A very common example of this type of still is the Boka (or Bokakob, named after it’s inventor).
The column contains two slant plates (pieces of copper), which are soldered in on an angle. As the vapour rises up through the column, it reaches the reflux condenser, condenses into liquid and falls down the column. Some of this falling distillate catches on the top plate which is slanted at a downward angle, and falls down onto the first plate due to the overlap of plates. It is then caught by the second slanted plate on the opposing side which is angled upwards, and fills that space until it overflows and falls back down the column.
The collection is controlled by a needle valve at the bottom plate, which when opened slightly, lets a small amount of the liquid distillate drip from the plate which is collected. By keeping this valve closed for the first half hour or so, the column gets itself into a sort of equilibrium, where the continual rising of vapour and falling condensate, refreshes the liquid held by the slant plates and allows higher/lighter alcohols to be held on the plates.
As the needle valve controls the release of the liquid as described, it is termed a Liquid Management style still.
Packing
Although the aim here is to understand the difference between various types of stills, and how their outputs are controlled, we will briefly discuss column packing here. This is in order to lead into the next section, and for a brief introduction on the interaction between rising vapour and falling liquid distillate. In the previously mentioned reflux stills, the columns are generally packed with a material containing a high surface area which also allows the vapour to pass through it. Most commonly used materials for this purpose are copper mesh rolled up, or stainless steel scrubbers. More on this can be researched further on the Aussie Distiller forum, but 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. Leaving a column in full reflux will repeat this process all over the packing material, forcing the lighter alcohols to sit towards the top of the column and the heavier alcohols further down the column. This is the process of separating the wash into its alcohol fractions, and collecting these off slowly is the process of fractional distillation. This process is known to strip all flavour from distillate, so the method is used for making neutrals (vodka).
In order to get a flavoured product (whisky, rum, brandy), minimal or no packing is used (as in a pot still), however a proven setup to achieving great flavour retention is a column which utilises plates at various levels throughout as its ‘packing’. ie. The area where the liquid distillate has contact with rising ethanol vapour. 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 95% alcohol by volume output. When distilling a whisky or rum, this is obviously not a desirable result, and a pot still or plated column is used.