REUSE
Information on labels and adhesives and their removal without residue during the washing process of reusable glass containers
To ensure that all kinds of stickers or labels and also the adhesive can be completely removed from reusable glass containers in a washing machine, the following should be observed:
1.Caustic solubility
The most important prerequisite first: Both stickers/labels and the adhesive or wet glue must be caustic-soluble! Only then, the glass containers can be cleaned without residue during the washing process.
2. Label or sticker: the influence of Printing ink, protective coating and hot foil stamping
Components such as hot foil stamping, varnish or printing ink seal the surface of the label and make it difficult for the caustic to penetrate the paper fibers in order to detach the adhesive. Applied primers (especially with digital printing systems such as Indigo) also seal the surface of the material additionally. The higher the proportion of such components on the label, the more difficult it will be to remove them later. In the case of #adhesive labels or #self-adhesive labels that are to be removed later by a caustic solution, full-surface coating and film lamination must therefore be avoided. Furthermore, it is advisable to rasterize areas and not to make formats of hot foil stamping too large.
The most suitable labels for reuse are still the traditional #wetglue labels.
3. Washing machine
The residue-free removal of labels, including self-adhesive labels, is ensured by a warm caustic bath. Temperature, caustic content and dwell time in the caustic bath depend on the recommendations of the adhesive manufacturer. For #self-adhesive labels, it is usually 1-1.5% caustic at a temperature of 60-80°C and ten to fifteen minutes exposure time, depending on the manufacturer. In the case of unprinted #wet-glue labels, detachment of the label may be possible after just one minute. The properties of the label paper as well as the above-mentioned treatments of the surface can influence and possibly extend the detachment time.
4. Return logistics / handling of the empties
Proper storage is a prerequisite for the removal of labels from used glass. Optimal storage of the empties is dry and protected from the weather. The adhesives in #adhesive labels and #self-adhesive labels react very quickly, especially to the effects of the weather. In addition, rain can cause the adhesive to dissolve and, when it subsequently dries, to adhere permanently. In general, the longer the empties are stored, the more difficult it is for the adhesive labels to come off later. If stored properly, the adhesive can be expected to adhere optimally for up to 12 months after labeling.
Due to the various influencing factors and material properties, no guarantee can be given as to removability.
For #wet glue labels, the storage instructions described above apply accordingly. The washability of the labels is of course significantly longer, since no adhesive is applied. With proper storage, paper labels have a storage time of many years.
5. Storage of labels / stickers
The storage of the labels before they are applied to the container also has an influence on their subsequent removability. The following applies here
– optimal storage of labels/stickers (20-23°C, 50-55% relative humidity)
– Storage in the dark (even neon tubes radiate in the UV range)
– Storage time of the labels as short as possible
6. Adhesive PP-labels (no-label-look)
Wash-off needs be considered case-by-case. However, adhesive PP-labels should be avoided from the ecological point of view since the recycling of washed-off labels is well established for paper and requires pure materials.
