Brian Gallacher, considers the best ink for decorating perfumery, personal care & prestige spirit glass bottles
Printing on glass bottles can be purely decorative but for our Stölzle Glass Group clients, it achieves branding and can also inform the customer of content details.
The ability to dispense with outer packaging can be valuable in today’s economic climate. An ever-increasing percentage of our bottle production is now decorated by one or other of the Stölzle Group’s decoration facilities.
The number of decorative techniques available has grown with technology:
• Acid etching, now electronically controlled, produces a pearlised finish to the glass surface that provides an attractive base for various printing effects;
• Screen printing applies designs and lettering to glass bottles by pressing colour inks through a metal screen. State-of –the-art printing machines enable two, three or four passes over the bottle to apply different colours automatically and elaborate effects are possible;
• Spraying lines can produce full cover spray, coating a glass container in one, even colour that can produce an effect of coloured glass, or can graduate colour. Using more than one spraying machine in line can gradually morph one colour into another, often with stunning effect;
• Then there are Automatic Decal Application and Pad Printing. Both provide limitless branding tools. Automatic application means spot-on accuracy of placement and easy integration into the decoration process;
• Foil Blocking can use a variety of metal foils, including silver and gold, to add an incontestable touch of luxury to a glass container.
Apart from acid etching, and foil blocking, the other printing methods mentioned above can use either ceramic enamels or organic inks. Each has advantages.
Ceramic enamels have long been regarded as standard for glass container decoration. Mainly inorganic, these inks are a mixture of colour pigments made from metal oxides and salts and finely ground glass particles, known as ‘frit’.
Ceramic enamels are supplied either as a liquid or in a solid form that requires to be heated before screening. These thermoplastic enamels allow more than one print per ‘pass’ on the printing machine without needing to be fired between prints, as is the case with the liquid, or ‘wet’ enamels.
Once applied, ceramics are fired in an electric or gas lehr at 580oC , enabling a permanent bond to be formed with the glass substrate. After firing, ceramic prints on glass containers have the advantage of being abrasion resistant and product resistant. There are, though, disadvantages to its use.
Environmental Legislation in the US and Europe regarding the use of certain heavy metals in ceramics has restricted the range of achievable colours. For instance, red and orange need to contain lead and cadmium to attain a satisfactorily bright and vibrant result.
After firing, the decorated glass has to be annealed – that is slowly cooled down to room temperature, a process that can take several hours. Both the firing and the cooling down process require machinery with large footprints, calling for considerable capital investment.
With regulations limiting the use of heavy metals in ceramic enamels and sprays, together with an inexorable rise in the cost of energy required in the firing and annealing process, the decorating industry began to look more and more seriously at eco-friendly organic inks and their vast range of colours.
Organic printing inks are basically screen printed in the same way as ceramics. However, organic inks remain wet until fired or cured. There are, though, automatic organic printing machines that can effect ‘flash’ curing with UV (ultra violet) lights between print stations, enabling multi-printing with one pass through the machine. Once printed, organic inks or sprays need curing at 170oC, in either electric or gas ovens. Lehrs with the heat reduced to 170oC can also be used to cure organics.
Initially organic inks had difficulty achieving adhesion with glass and suffered from abrasion and product resistance (damage caused by spillage from the container’s contents). Decorators, given a free choice, would always choose to print with ceramic to limit the possible quality risks. However, organic inks have improved significantly over the years in both these areas, and market confidence is much higher than it was when they were first developed. Testing for both these aspects with organics is a necessary quality control activity at both the new product development stage and in production.
Organic printing inks offer a limitless available colour range and can also offer transparent and opaque finishes. Ceramics have a wide range but with limits, and they cost more to fire.
In the Stölzle Glass Group decoration factories, the prestige and beauty division uses ceramics or organics depending on the type of colour and artwork to be used. Nobody, though, requests ceramic sprays these days and they are no longer offered by Stölzle. Ciroc Vodka bottles are printed in ceramic and then over sprayed with organic. Both our graduated and full cover sprays are organic; we now have a production area dedicated to organics.
Taking both prestige spirits and perfumery and personal care markets into consideration, it seems at present there is a healthy demand for both ceramic and organic printing inks.