A thin layer of tin oxide is formed on the glass surface in a matter of seconds. The tin oxide layer prevents
any direct glass-to-glass contact, which preserves the strength of the glass.
Second, the tin oxide layer is the basis for enhanced adhesion of the cold-end coating. The cold-end
coating, a polyethylene wax, is sprayed on the tin oxide base after the cooling lehr. This coating causes the
glass surface to become slippery. The resulting low friction coefficient diminishes the forces in bottle-to bottle
contact.
Bottles coated in this way move freely through inspection and filling lines and do not sustain surface
damage. A damaged surface looks bad to the consumer and weakens the glass, often resulting in premature
breakage.
In addition, instead of accepting an increase of some 20 per cent in bursting pressure, the bottle may
be made lighter while still retaining its strength.
