Here - PFI Group

Which Shoelace
is Suitable for Which Shoe?
Or more fittingly: What must a shoelace be able to
endure and what should it look like? These are in
fact the principal aspects determining the proper
choice:
Since professional, work, safety, or hiking footwear
has to withstand substantially greater stresses than
lightweight leisure shoes, the laces clearly have to
cope with more stringent demands. Here it is recommended
to use thick, robust, high tensile strength
laces made of synthetic fibres. Ideally, they should
also have a round cross section because they can then
accommodate a core at their centre – as described in
this article – which enhances their strength. Shoelaces
made in this way resist abrasion and withstand
high tensile forces better than flat laces made of
cotton. Anybody who has tried their hand at mountaineering
will certainly appreciate the importance
of strong laces and the security of firmly laced-up
footgear.
Casual leisure footwear or seasonal goods which just
happen to be in fashion are subject to far less stress.
Imagination knows no bounds with regard to material,
colour, and production method. Even shoes with
zip fasteners may have additional laces. Their original
purpose as a means of closing a shoe no longer
plays any role. The laces merely serve as decoration.
The visual appearance and the colour of laces and
the way in which they are tied have been playing an
ever-greater role in recent years. There are even web
pages devoted to the art of lace tying, which present
a wealth of extraordinary and quirky ways of lacing
shoes – just try googling “tying shoelaces”!
01.2011
Magazine of the Test and Research Institute Pirmasens
In the sports sector, flat, flexible, and extensible
laces have proved their value for running shoes because
they are not so stiff as thick round laces. The
elasticity of such shoelaces also assures a firmer fit
of the shoes. Moreover, knots in such laces do not
come undone so quickly. This distinct practical advantage
predestines the flat variants for use in children’s
shoes: fewer undone shoelaces mean fewer
tumbles.
There can be many reasons for shoelaces coming undone:
On the one hand, the choice of material plays
an importance role. If it is fairly rough it will offer
more resistance to opening of knots and bows. On
the other hand, the thickness and structure of the
laces (density of braiding) will have an effect on their
stiffness. The more inflexible the laces, the easier the
carefully laced-up shoe will come undone. In addition
to starting material and method of production,
substances applied to the material in the course of
production also play an important role. They may
influence not only the roughness but also the flexibility
of the laces. There is currently no standard
test proceedure for assessing how readily shoelaces
come undone during wear or which laces have superior
properties in this respect compared to competing
products. However, PFI does undertake a test
to estimate the probability that a knot will come
undone, paying due attention to structure, stiffness,
and frictional properties of laces and material.
On no account should we forget the kind of footwear
which has to meet particularly stringent demands,
such as firefighter boots. These have to withstand
heat and fire and should clearly never catch
alight. They therefore contain a certain amount of
fire retardants.
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