Mould swabbing operation is key for the glass forming process.  Swabbing lubricants are a combination of different chemicals and the use of them combined with the high temperature creates undesired effects on equipment, on glass and on people: corrosion and smoke. Glassline® lubricants offer the best compromise. 

Swabbing lubricants do contain sulphur; this chemical is necessary as it plays a role as lubricating improver when extreme pressure (EP) is present. EP conditions is definitely present when the gob is formed to a glass bottle through the different processes (blow/blow, press/blow or NNPB). Unfortunately, sulphur (and for sure excess of sulphur) has a metal corrosive impact, especially on bronze and bronze/nickel moulds; this negative effect will directly impact the quality and lifetime of mould equipment but also indirectly, glass bottles defects can occurred.

VDV Lubricants decided in 2016, in partnership with a specialised Belgian research institute (BIL), to identify and quantify the corrosion effect of swabbing lubricants during their application on heated metal surfaces; the objective was to come out with at least 1 solution.

Without going in details, below are some basic data from this study:

* Swabbing lubricants tested:

o Reference = typical swabbing formulation containing standard base oil, a package of additives (including sulphur based products) and graphite.

o Reference containing five different selected anti-corrosive agents

* Test conditions: 

o Copper plated heated at 500°C. Copper has been selected as it is the most sensitive material to observe corrosion.

o During 10 days and each 20 minutes, application of swabbing lubricant droplets on the heated metal surface.

The results expected were very present and can be summarized as follows:

o Surface damaged = metal losses and irregular surface, see also image 1

o Without anti-corrosive agent is the average damage:

* 120 to 212µm metal losses or 13 to 23% of original surface depth

o With anti-corrosive agents is the average damage:

* 28 to 166µm metal losses or 3 to 18% of original surface depth

Best result is only an average of 3% metal loss/depth damage.

Main technical conclusions from this study are the effective impact of corrosion damage of metal surface during swabbing operation and the existing option to considerably limit this negative effect.

Putting this within the glass manufacturing activity, it is clear that mould metal losses and surface damages are potential risks to create glass inclusions, metal contaminations of the inner content of the bottle and so leading to quality claims. Additionally, the lifetime of the moulds is reduced and will generate cost at maintenance and purchasing levels.

The good news is really that the solutions exists and VDV Lubricants is now able to update on request its Glassline® swabbing lubricants to offer glass plants a controlled and limited corrosion impact on its mould equipment.

In fact this is the most important challenge as it concerns directly the health of production operators; let’s also not forget that air contamination in the production area influences the inner content of produced bottles as well.

Swabbing lubricants are a combination of a liquid phase composed of a base oil with lubricant additives, and a solid phase composed of graphite.

As soon the swabbing lubricants comes in in contact with the heated mould surface, the main part of the liquid phase, for sure the base oil, will almost instantly convert to a gaseous phase, this phenomena is unavoidable. In order to limit the generated swabbing smoke, the only option is to reduce the use of lubricant; this can be achieved by a manual “dry” swabbing or even better, by automatic swabbing.

As soon the quantity of smoke is controlled, it is a priority to look then closer at the content of it … as you cannot always see or smell what’s in there! VDV Lubricants, as a responsible chemical manufacturer, has taken the initiative to have a complete and representative study (performed by Vito Research Center, Belgium) about the smoke quality generated during swabbing operation.

The conditions of this study are:

* Heated metal surface – avg. 450°C

* Weight-controlled lubricant dosage system

* Closed atmosphere to collect the entire gaseous components

* Gas-analyse equipment’s

We selected for this project 1 swabbing lubricant from competition, 1 standard Glassline® swabbing lubricant and our latest innovative product, Glassline® SwabPharma: this latest product has been developed by VDV Lubricants and patented for its properties towards a high level of safe and clean swabbing.

Some conclusions:

* Swabbing lubricants are chemicals; when in contact with heated mould surface, they will burn off and always create smoke that contains chemical components

* Swabbing smoke (also called oil mist) usually contains components that are subject of healthy high concerns, as inhaled by production operators all day long

* Depending on the air recirculation in the production area, limited exposure values established by national authorities are exceeded

* Glassline® SwabPharma is the first product on the market that offers reduced risks of air contamination.