Leather Bursnshing

Leather burnishing & polishing

Existing procedure •

Darkening of edges or burning on edges result on increased of shades/tones by changing surface hardness & characteristics (specular reflection).

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Conventional process done with Bar wax (solid natural wax) yellow in appearance applied on rotated wheel where panels to be in touch with!

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An abrasive polishing process that makes a rough, non-reflective, surface into a smooth, highly light reflective (glossy) surface!

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This is accomplished with machinery that moves an abrasive pad at high rotational speeds making the process highly effective and efficient.

Wax: •

Refers to a class of chemical compounds that are plastic (malleable) near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid.

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Waxes are insoluble in water but soluble in organic, nonpolar solvents.

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All waxes are organic compounds, both synthetic and naturally occurring materials which are conventional solid ester wax

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It has multiple and broad melting curves at the temperature range of 45oC to 60oC.

Abstract: •

Leather finishing auxiliaries available in market with high degree of property like non coating, water soluble & neutral /transparent in color that responds to both minimal mechanical action & temperature.

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Result of HMP (Heat & mechanical process) transparent layers where above the yield point & in plastic region gives darken shades /burned effect as well as polished looks on all the way!

SEM VIEW: Scanning electron microscope

a: Limed pelt d: burnished

b: dye crust

c: coated/finished

Chemical property of Spray wax  Emulsion of natural waxes  Water soluble  pH (undiluted) – 9  Solids content - 17.5%- Spray wax

Bursnhing: •

Over spray on working panels (required width) method gives thin film on top! as this is become inherent to surface with chemically (polarity reaction)

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Coated panels /region where contacted to rotating spindle (HMP) & result will abrasive action & heat evolution would increase surface hardness.

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Film stressed /strained to reach above yield point at plastic region gives burnished effects!

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Changing from normal refractive index to specular Reflexion

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Rotating shaft RPM : 2000 to 2500

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Depth of the burnishing: 0.2 to 0.3mm where eventually increases the surface hardness!

Polishing:

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Tg & Tm where important factors & considering point for polishing.

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Heat with minimal mechanical action on film which reaches to melting point & ultimate results of glossy & smooth surface appearance,

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Rotating shaft RPM : 1000 to 1600

Cut and polish motions:

Cut motion: •

smooth surface, semi-bright & uniform:

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The work piece should be moved against the direction of the wheel, using a medium to hard pressure.

Color motion: •

bright, shiny & clean surface:

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The work piece should be moved toward the direction of the wheel, using a medium to light pressure.

Burnishing speed and pressure  Rotating RPM :2000 to 2500  The correct pressure must be applied to the work piece to provide the best finish economically and safely.

 Inadequate pressure result could be appropriate – Waxy feel & appearance on surface

 Excessive pressure will cause the buffing wheel to slow down or actually collapse. This can also result in burn marks on work piece.

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*The surface hardness is proportional to depth of penetration. The increases the number of tool passes / burnishing force leads to increase of surface hardness.

Tool kit for Burnishing & Polishing Canton flannel wheel

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Canton flannel is very soft, and this wheel is loosely stitched!

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So the layers of Cotton cloth flare out to give a wide angle ultra-smooth polishing & burnishing

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Wheel suitable to most delicate items such as softy leather.

Loose cotton wheel

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The main purpose of a loose cotton wheel is to polish and cut in a similar manner to the Spiral sewn wheel,

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Except that this wheel, not being tightly stitched together, will collapse, allowing the cotton to get into uncontrollable places more easily & result will scratch appearance on working panels.

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If you have an object with fine details and imprints then this is right choice of wheel.

Leather characteristic for burnishing & polishing •

Conventional finishing film : PH on any leather should be in acidic range (3.5 to 6.5)

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Previous procedure – Superficial /surface transformation & there’s no inherent zone for polar attraction (surface coating & physical attraction).

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New procedure –Selected wax emulsion in alkali PH (9 to 9.5) & eventually will have chemical bonding & effects become inherent to material.

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Finish film – Top coats with protein binder (high or medium) facilitate /enhancing the burnishing & polishing appearance.

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Matt finish film – Doesn’t respond well against to both spray or bar wax procedure.

Result & Conclusion: •

New procedure: changes from earlier process that application of wax been done directly on material,

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Easy of process to Define width & consistent of appearance on across the collection

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HMP (rotational abrasion): Heat & mechanical operation needed to achieve to both polishing & burnishing.

Updation/ Alternate process:

Under development

 Heat & roller pressing: Spraying panels & passes through feed roller contribute desired effects!

 Only Heat Procedure: Spraying & subsequent heating in hot chamber aid the appropriate appearance!