Leather Finishing Methods - Campbell

Leather Finishing Methods
Dan Naegle, Campbell - Randall Machinery
Once a hide finishes the tanning process, the leather can be manipulated for a variety of
looks and textures. At the tannery the leather undergoes a series of wet operations for
coloring and oiling. After the hide dries and it is in the “naked state”, it can be mechanically conditioned for different look or feel. Some of these same techniques can be used
at your work bench. Beyond dying and oiling the leather, we’ll take a look at physical
conditioning methods to give plain old leather a new and different look.
Staking:
Staking is a method of massaging a hide to make the
leather more pliable. In years past, a operator would hold
a skin against a bar while a staking machine would grab
the hide with rubber rollers and blunt blades to pull and
flex the skin. This stretching makes the leather softer and
more pliable. Tanneries refer to this characteristic as temper.
Source: Cudahy Tanning, division of Prime Tanning
Modern tanneries use large machines with many thumb-size
pins that oscillate and pound the leather as it travels along
a conveyor. This same technique can be applied by rolling,
stretching, or massaging a stiff piece of leather at the bench.
Buffing:
Buffing is a light sanding operation to either side of the hide. Buffing the underside will improve the nap and produce a velvety texture
known as suede, while buffing the grain surface will smooth out some
natural imperfections such as scratches, scars, etc.
Full grain leather has nothing removed except the hair, and possesses
the original grain of the animal. This is the strongest portion of the
hide. Buffing the grain with a emery wheel will produce an altered grain known as snuffed top
grain, hand buff, nubuck leather, or corrected top grain. This is typically the same as a fulltop
grain leather, but the hide is lightly sanded to remove only the top of the hair follicles. A tannery
will use a machine to buff approximately 1/64 in or 1oz in thickness from the grain. This should
leave a portion of the grain on the entire hide and results in a cleaner surface.
Boarding:
Boarding leather accentuates grain or produces additional wrinkles by folding the
grain side and working the leather back
and forth.
A boarding machine consists of 2 rollers
with a blunt
blade that gets
pushed between the rollers. The skin
travels around
the blade and
is flexed tightly
due to the nipping action of the rollers. Aggressive boarding can create a wrinkled or
distressed look to the leather.
At the bench,
hand boarding
is done with a
curved cork board
attached to the
worker’s arm.
The worker rolls
the board over
the folded skin until the desired look is
achieved.
Hand slickering is used on delicate leathers and soft
leathers,
where the
harsher action of the
staking or
boarding
machines would damage or mark the surface of the leather. The leather is wrapped
around the hand slicker which is pushed
along the surface of a table.
Plating (Embossing):
One of the final conditioning processes
is embossing the
hide with heat and
pressure to create a
chosen grain in the
surface of the hide.
A unique design can
be used or an imitation of full grain. Sometimes leathers are
embossed to make them appear to be another leather, such as embossing an alligator or ostrich pattern into cowhide.
It requires hundreds of tons of pressure to
emboss a full hide. Some shops my find
a small scale plate embossing press usefull for cut pieces, especially for embossing saddle parts or hand bag leathers. If
a plate embosser is not in the budget, a
heavy duty rotary embosser can do the
trick. Some models, like the Randall R32,
will accept rolls dies up to 7 inches wide
to emboss an imitation grain on straps or
small leather pieces.
Glazing:
On of the oldest finishing methods, glazing
is a process of polishing the grain surface
under heavy pressure with a roller of agate, glass or steel. A protein additive, albumin – derived from egg whites, is applied
to the surface of the leather and allowed
to dry. The dried leather is then placed on
a glazing jack, a machine equipped with a
solid roller that quickly strokes of the surface of the leather by means of reciprocating arm.
The pressure and the number of strokes
can be controlled by the operator to
achieve the desired degree of shine, thus
enhancing color tones and a finish in different areas of the skin as needed. The friction of the glass rubbing across the surface
creates heat and hardens the finish, while
the quick action produces a mirror-like
surface. The heat of the glazing jack also
causes darkening of the colors and raising
of some of the oils in the leather. The re-
sulting finish produces a natural depth and
beauty to the leather.
Traditional glazing can be costly, as it may
be necessary to apply as many as six different coats involving several glazings,
platings, staking and brushing operations
to bring the desired characteristics. It is
difficult to reproduce glazed finishes with
a modern mechanized processes. Glazing
is confined to the more expensive types
of leathers, such as reptile, kid, and highgrade calf. Glazed finishes are also known
as Sleeked (done by hand with a copper
tool), and Glassing (done by hand with a
lump of glass used as the glazing tool). A
glazing jack is a machine that duplicates
the hand process, and can be used to do
several types of finishes, such as a pumice
rod for buffing, and boarding and graining
operation.
Brushing:
Brushing or polishing
machines can be used to
remove surface defects,
polish finished products,
or brushing effects for
vintage and distressed
looks. Horse hair brushes
are great for polishing a hide surface and
can be used with polishes or waxes. Felt
wheels do an excellent job without leaving
or strings behind. You can also use cloth
or yarn mops. For a different look, brush
with special abrasive or soft wire wheel to
age the leather. This technique is popular
for fashion accessories. Don’t be afraid to
experiment a little. You even might be able
to turn that sow’s ear into a silk purse!