Why the Carbo Classic Base is a genuine classic

In my most recent blog article, I dealt with the various technical requirements bottle bases have to meet.

In terms of internal-pressure stability, the most technically sophisticated base is without a doubt the Carbo Classic Base, also known as the petaloid base. The word “petaloid” is etymologically derived from Greek and Neo-Latin, and in its original meaning simply signifies “petal-shaped”. In actual fact, the Ancient Greek word “penta”(= five) has nothing to do with the derivation of the petaloid base, although this is often erroneously assumed, due to the five feet usually featured.

So much for one part, the name. Now, with the new base designation, the Krones petaloid base has now finally been given the appellation of “Classic” – but why is that the case?

The Carbo Classic Base results from long years of development and optimisation work on the original petaloid bases, which had been in use at Krones AG since the 1990s. Data were steadily collected and analysed, and factored into the design together with plenty of empirical feedback. The Carbo Classic Base consequently constitutes an optimal compromise between the multifaceted technical requirements involved. These empirical values have been incorporated in the design for parameters like prior circular diameter, base height, clearance, number of footlets, and stabilising-rib geometry. The diagram below illustrates these terms:

Standkreisdurchmesser: Prior circular diameter; Bodenfreiheit: Clearance; Bodenhöhe: Base height; Zugbandgeometrie: Stabilising-rib geometry

Almost no other base is so closely associated with PET bottles as the Carbo Classic Base. This, however, is both a curse and a blessing. A curse, for marketing reasons, since our clients in the premium sector often prefer a container that visually resembles its glass counterpart, and petaloid bases with their “PET look” generally tend to fall short in this respect. A blessing, because this base is absolutely reliable as a technical design feature and therefore a genuine “classic”. This technical reliability results from continual design enhancement, factoring in further technical data and the market’s current requirements. So this base can be used worldwide in every climate zone given the appropriate modifications.

In addition to its technical dependability, using this base also offers financial advantages for our clients, generated from energy* and material** savings, plus high levels of process reliability.

For the above-mentioned reasons, the Krones Carbo Classic Base was technically patented in 2008 and its geometrical contour protected together with the associated free-form areas. Bastian Tissmer from the PET Packaging Development and Consulting Group was crucially involved in the development work concerned, so he could hardly be better informed about the development work and the patenting procedure concerned.

Bastian, how was the Carbo Classic Base developed, and who was involved in this process?

Around 2007, there were recurrent problems with the petaloid bases then being used. New specifications demanded by our key account clients could not be met in the thermo-test and the stress crack test. This meant that up to four base cups had to be produced for a sampling job before a base finally worked properly. This was extremely expensive and time-consuming, of course. Which is why a “base team” was formed – consisting of Heiner Deyerl, Gerhard Schuster and me – tasked with solving the problems involved. One year of intensive work under extreme time pressure finally led to the present-day Carbo Classic Base and some organisational changes, like the introduction of a base code for unambiguous identification and evaluation of the bases used.

When and why was this base patented?

The Carbo Classic Base was first registered as a utility patent, since the development work was proceeding under intense time pressure. In 2008, the technical patent was then registered, and published in 2011. The technical innovation involved (which is, of course, determinant for the granting of a patent) was that this is the first base to be designed on the basis of free-form areas. In contrast to the previous “building-block construction”, this results in a very material- and production-friendly final geometry.

So why do you see the Krones Carbo Classic Base as a genuine classic?

Because right up to the present day it’s the standard base for CSD bottles and with very minor modifications achieves absolutely top performance – not least with appropriate lightweighting.


* for heating and blow-moulding pressure

** lower base weight, approx. 3 g in the case of a 1.5-litre bottle