Material: Container
Glass
Issue: Historically, label adhesives
used by bottlers were designed for easy removal
so that bottlers could recover their own bottles
through local buy-back programs and wash the
containers for re-use.
With most bottle-washing programs discontinued,
and in response to marketing and operational
considerations, many have converted to more
convenient and durable label adhesives.
These adhesives, which include press-applied
and plastic labels, pose a major barrier to
successful bottle washing because they do not
readily come off in the caustic baths used in
bottle washing machines.
Best
Practice: Several
strategies may help to mitigate the problems
associated with more durable label adhesives.
The best way is to convince bottlers
to use washing-friendly labels.
This should be part of an overall marketing
plan for the bottle-washing program (see Elements
of a Bottle-Washing Program Best Practice).
Second, understanding the fundamental
technology of label adhesives makes it possible
to develop strategies for resolving difficulties
with durable label adhesives.
There are several primary glue types, including wet
glues, high release dry glues, and press-applied
adhesives (i.e., self-adhesive labels).
Wet glues are water-based, and easily
release in hot caustic solutions.
Press-applied labels, however, are more
durable and may actually strengthen their bonds
in response to heat, preventing them from releasing
when washed.
Since most bottle washing equipment uses
a pressure wash of hot caustic solution to clean
and sterilize bottles, this is a significant
issue for bottle-washing operations.
It may be necessary to use equipment that submerges
the bottles in a caustic solution for an extended
period, rather than just spraying them.
In addition, it may be necessary to modify
the temperature, time, and caustic level of
the soak to weaken the adhesives sufficiently
for removal. Of course increasing all of these
parameters also adds costs to the operation.
Unfortunately for bottle washers, the trend is toward
the use of press-applied labels for several
reasons. First, wet-glue labeling equipment generally
costs more than press-applied labeling equipment,
despite wet glue equipment’s lower variable
costs of operation.
Second, condensation has less effect
on press-applied labels. When bottles are filled with cold liquids,
condensation immediately forms on the outside
of the bottle. High release dry glues cannot be applied over
condensation.
Wet glues can be applied, but the quality
of the label placement is not as good as that
achieved with press-applied labels.
Condensation during subsequent storage
and handling can also shift wet glue labels.
There are certain special adhesives which can be used
with press-applied labeling systems that would
allow removal in the hot caustic solutions used
by bottle washers, but very few producers are
interested in using
hem because of cost. Ninety percent of new labeling machines in the wine industry now
use press-applied type labels. Thirty percent
of new labeling machines in the micro-brewing
industry use press-applied type labels. With micro-brewing a potential market for bottle washing, and with
the use of press-applied labels less common
but growing, it will be important to monitor
this industry.
Some bottles also come pre-labeled from glass companies,
either with press-applied plastic labels or
with applied ceramic labels.
These labels pose the most serious issues
for bottle washing due to the impervious label
surface preventing penetration of the caustic
solution. In addition, recent developments in container coatings mean that
more bottles will have either applied ceramic
labels or sprayed-on clear plastic coatings,
neither of which can be used in bottle washing
programs, further complicating label removal.
Implementation: The problems discussed above
enhance the idea that bottle washing might most
effectively be undertaken by either wine or
beer producers’ cooperatives.
Producer cooperatives receive some unique
tax considerations from the federal government
and would have a vested interest in cooperating
fully with each other on labeling issues.
However they are structured, bottle-washing
programs must be tailored to existing markets,
usually a concentration of breweries or wineries,
in order to achieve a critical mass of both
washable bottles and final sales.
Benefits:
The
ability to remove label adhesives is critical
to the viability of any bottle-washing program.
There must be a comprehensive knowledge
of the containers the program will handle and
the label adhesives being used.
Laboratory testing of the tenacity of
the adhesives under simulated bottle washing
conditions, followed by pilot production, will
help to determine the feasibility of a full-scale
operation.
Application
Sites: Bottle-washing
operations, bottling companies.
Contact: For more information about this Best Practice, contact
CWC, mailto:info@cwc.org.
References: A Model for a Bottle-Washing
Program, ReTAP, Clean Washington Center Report
GL-93-8, 1993. Evans, Dick, CGC/ENCORE, INC., Richmond, CA. Metz, David, Prospero
Equipment Corporation, Pleasantville, NY.
Issue Date / Update: November 1996
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