What packing to choose? Steel Scrubbers or Spiral Primsatic Packing (SPP)? Stainless Steel or Copper?


Well, the best combination is a copper still with stainless packing. Why?
The height and type of filling have the most significant impact on the quality of the product. The resolving power of a distillation column depends on the number of so-called "theoretical plates." Where does this term come from?

Large industrial distillation columns operate on the principle of repeated condensation and evaporation from these plates. A home equivalent of such a solution is a plate still, which contains no filling, just sieve plates. Home distillation reflux stills for spirits, to fit within a "home" height, use filling (packing) instead of plates—whether scrubbers, spp, or extremely inefficient "inventions" like broken glass or lathe shavings. Essentially, the packing also condenses and re-evaporates the condensate on its surface, behaving like a plate and hence some volume of it is called a theoretical plate.

The Key Concept: HETP (Height Equivalent to a Theoretical Plate)


A specific height of a given type of packing corresponds to one actual plate. This parameter is known as HETP (Height Equivalent to a Theoretical Plate). Since the filling is "three-dimensional," unlike a flat plate, there is more surface area within a given volume, allowing for more condensation and evaporation. Imagine a flat A4 paper sheet—its surface area on a desk is 62 cm², but if you crumple it, the same surface area fits into 4 cm², just taking up more height. The same principle applies to column packing—the more surface area per unit volume, the better for the process.

For example, the height of a theoretical plate for scrubbers is about 4 cm, and for stainless SPP, it is 2 cm. So, every 2 cm of column height corresponds to one "plate," one distillation. Of course, the HETP parameter changes during the process (the phenomenon of "plate stretching") due to constant alcohol loss (it evaporates from the boiler and is taken out), so it's impossible to "simulate" a plated column with a distillation column where the number of plates is constant.

The more plates in a column, the greater its resolving power. For contrast, broken glass has a plate height of about 13 cm. In 100 cm of steel scrubber filling, we have about 25 theoretical plates, with springs—50, and with broken glass, just over 7.5.

What Should the Packing Be Made Of? Steel or Copper?


Paradoxically, stainless steel.

Why? Prismatic springs (or SPP) made of acid-resistant steel have a larger surface area than just the surface area of the wire from which they are made. Between the coils, a small triangle forms during the process, where a film of condensate appears (like in a bubble-blowing ring)—so we have more surface area than the material used to make the spring.

Unfortunately, due to the production method involving less springy copper wire than the same-diameter steel wire, copper springs form a different shape on the prism (die). As a result, "eyes" for reflux do not form, and the springs have a much worse p/v (surface/volume) parameter.

While the theoretical plate height for stainless steel springs ranges from 2-3 cm, for copper spp, it's about 12 cm. The more plates, the purer the distillate, so using copper springs worsens the product quality! If you use copper still, do not use copper packing. 

What About Scrubbers?


Stainless scrubbers are made by rolling flat stainless wire. These "ribbons" of wire are then tightly wound into a ball, which is also excellent for column packing. Beware of so-called "copper scrubbers"—no such product exists. Copper is too soft; it crushes and breaks when rolled this way. Scrubbers sold as "copper" are made of black steel coated with a thin layer of copper. Unfortunately, this layer wears off quickly—after two or three processes, it no longer exists, and the scrubber (made of black steel) corrodes, causing rust... Even worse, soldering cleaners, which contain lead, are sometimes sold as "scrubbers." There is no reason to even consider filling a copper reflux still with copper filling, as it degrades the quality of the spirit unnecessarily!

In stainless steel still, which usually produces distillate with much worse odor and taste, a catalytic filter section filled with copper springs is essential to mask the "eggy" smell of the distillate caused by sulfur compounds. Therefore, owners of stainless steel equipment, much worse than copper apparatus, must rely on dubious quality filling.

In the case of a copper column, the inner surface of the column itself is enough to provide catalytic properties and reduce undesirable fractions, allowing the entire useful volume of the column to be filled with high-efficiency filling, ensuring the resolving power needed to obtain an odorless product of 96%+. Therefore, the best choice for filling a copper distillation still is stainless steel prismatic packing. It is worth mentioning that in this configuration, you don't need to maintain the catalytic filter every process—empty it, etch it, neutralize it, dry it, and refill it. A copper column with SS packing is virtually maintenance-free!

If you want to replace your column's filling from scrubbers to prismatic springs, you can buy them here.

Clicking the link above, you will find Henitom (Trigra polish brand) packing, specially selected for optimal performance in your distiller. The required amount is described in the product description for each type of column and pot-still