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PROGRESS SEQUENCE. Small Skull

A PROGRESSIVE ILLUSTRATION OF

KILN CASTING

SMALL, LEAD CRYSTAL GLASS SKULLS.  

The following is a low tech, backyard casting sequence from a small sculpture studio nestled in isolated, bush clad hills of New Zealand’s Northland.

 

mother mold PROGRESS SEQUENCE. Small Skull

Looks like something ready to go in the bin?

This is the casing or ‘Mother Mold’ which supports the rubber inside. In this instance it is made with fiberglass for strength and durability. Often made with gypsum, ‘Plaster of Paris’, for convenience.

Plaster, short lived and fragile compared to fiberglass.

mother mold open PROGRESS SEQUENCE. Small Skull

Opened up, the rubber ‘skin’ into which wax is poured at 90c, is now shown fitting inside the ‘glass casing. 

Depending on ambient temperature the wax may be cold in 4 hours or thereabouts and ready for removal.

 

the rubber PROGRESS SEQUENCE. Small Skull

The catalytic, RTV silicon rubber skin mold for the making of small wax skulls.

Or another medium if such were desired. Polyester, acrylic, cements, reconstructed media, the choices are many and varied.

 

emerging PROGRESS SEQUENCE. Small Skull

Here the ‘master’ is being withdrawn from the rubber ‘skin. This silicon rubber is a very strong, tear resistant, flexible substance and when designed well for such a mold as this will be capable of innumerable reproductions before deterioration renders it unusable.

 

extracted PROGRESS SEQUENCE. Small Skull

The master pattern released and the rubber ready for wax.

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SMALL, CAST WAX, SKULL

The quality of a wax casting is purely a personal criteria. Here particular attention was focused on the master before the rubber mold was made. Any unwanted blemish on the master would be also on the subsequent wax castings and require unnecessary time in the cleaning up before plaster molding. Or if not dealt to in the wax stage then eventually in the cast glass.

hand held skull PROGRESS SEQUENCE. Small Skull

A clean cast in wax with minimal fettling.

sprued and cupped PROGRESS SEQUENCE. Small Skull

Sprued and cupped ready for the plaster molding process.

spruedcupped 2 PROGRESS SEQUENCE. Small Skull

Seam and handling damage requiring attention prior to plaster molding.

spruedcupped 3 PROGRESS SEQUENCE. Small Skull

 

to fettle PROGRESS SEQUENCE. Small Skull

Closing in on the most pertinent ‘dings’!

Evident in the upper portion of the image …. A finger nail mark gouged out in the enthusiasm when removing the wax from the rubber!

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FETTLING THE WAX SKULLS

fettlingwax72 PROGRESS SEQUENCE. Small Skull

The flame is burning and wax skulls are ready to clean up before investing in plaster mold.

 

to fettle2 72 PROGRESS SEQUENCE. Small Skull

Quick spots of hot wax to fill marks and the odd blemish from handling. The selection of dental  wax working tools assist in speeding the process.

 

to fettle base 72 PROGRESS SEQUENCE. Small Skull

On these small wax skulls this is the only part line and is quite easy to remove. The gouge from finger nail enthusiasm now filled and firm enough to dress back.

 

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Finished and almost ready to mold up in plaster.

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PLASTER MOLDING OF THE WAX PATTERNS.

The elementary mold mix is one kg of gypsum, one kg of silicon flour to one liter of water.

 

 72 PROGRESS SEQUENCE. Small Skull

Critical attention applying this pre-coat of molding plaster is crucial to eliminating air bubbles on the surface of the sticky wax.  Any bubbles caught here will be on the subsequent cast glass and require tools and time to remove.  

plastered 2a 72 PROGRESS SEQUENCE. Small Skull

Attention…          quickly…. before the plaster starts setting.  

plastered 5a 72 PROGRESS SEQUENCE. Small Skull

As soon as that all important initial film is covering the wax pattern and air eliminated a repeated pouring of the still liquid plaster mix builds up the inner layer for the final molding.   

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The wax skull now covered with the pre-coat of molding plaster

plastered 3 72 PROGRESS SEQUENCE. Small Skull

In container for filling with plaster investment….

 

plasterencased 72 PROGRESS SEQUENCE. Small Skull

Invested ….. Wax encapsulated within the plaster mold matrix….

 

plastered 5 721 PROGRESS SEQUENCE. Small Skull

Ready to dewax by steaming out.

 

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STEAMING OUT OF THE WAX SKULL

 

dewax 1 PROGRESS SEQUENCE. Small Skull
Steaming out the wax skull

 Steam being directed into the openings of the plaster molds to melt out the wax skulls.

 

dewax 2 PROGRESS SEQUENCE. Small Skull
Closer view of applying the steaming out process

 A closer view of introducing the steaming process showing the stalicmites and stalictites of molten wax building up.

 

dewax 3 PROGRESS SEQUENCE. Small Skull
Showing the dewaxing of the Small Skull Molds

 

 

dewax 4 PROGRESS SEQUENCE. Small Skull
A closer detail of the steaming out process.

A detail showing the wax base still in place at the initial introduction of the steam pipe.

 

dewax 5 PROGRESS SEQUENCE. Small Skull
A close up of the dewax sequence.

The mold now clean of wax leaving a cavity in the form of the wax skull. Almost ready to prepare for glass and kiln.

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CLEAN & EMPTY PLASTER MOLD 

 

dewaxwed PROGRESS SEQUENCE. Small Skull

Dewaxed Plaster Mold for Small Skull.

Steamed out, clean and waiting glass.

Extreme care to prevent contaminants from falling into the skull cavity.
 
dewaxwedglass PROGRESS SEQUENCE. Small Skull

The Appropriate Volume of Glass to Fill the Skull Plaster Mold

 In this instance a 1 kilo billet of ‘Rhubarb’dichroic Lead Crystal is the required volume of glass to cast this Small Skull.
breakingweighingbillets PROGRESS SEQUENCE. Small Skull

Appropriate Measures of Glass For Casting

 A hammer to break the crystal into appropriate weights for relative molds and patterns. Hand held in tough leather gloves and covered with news paper to shield from flying splinters.  Or displacement methodswith unknown weights are the best alterative to work out volumes required.

 

kiln loaded lower PROGRESS SEQUENCE. Small Skull

Loaded Lower Level of Kiln Ready for Firing

The lower level of this particular kiln used for  Kiln Casting Glass  is now filled with plaster molds of various patterns. Each with the appropriate amount of glass gently place in the resevoir .

 

kiln loaded lowerhalfshelf PROGRESS SEQUENCE. Small Skull

This lower level is overlaid with the kiln shelf.

Kiln shelving being set in place to support the upper level of plaster molds for
Casting the Lead Crystal Glass.

 

kiln loaded upper1 PROGRESS SEQUENCE. Small Skull

The upper layer of Kiln Loaded Ready to Turn on.

All fully loaded, the lid ready to drop and program the control computer for this firing of

Casting Lead Crystal Glass Skulls

With the accompanying plaster molds of other patterns a full week will be required for this sequence of stages to complete the cycle for a successful cast. Under the extreme conditions within the kiln during firing any small oversight in the preparation of these molds could result in disasterous consequences. 

Now the seemingly long wait!!    Patience !! 

 

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Six days Later

 Fired & Ready to Open the Cast Glass Molds

 

opening1 PROGRESS SEQUENCE. Small Skull

Fired & Ready to Open

Upper and lower levels now cast and ready to break open and see the results of this firing of Lead Crystal Glass 
opening2 PROGRESS SEQUENCE. Small Skull
The lower level of Kiln Cast Glass

 

Skull removed from Kiln and now to be broken open………
demold 1 PROGRESS SEQUENCE. Small Skull 
The precoat of plaster evident as a separate layer in the mold matrix.

demold 2 PROGRESS SEQUENCE. Small Skull

 

demold 3 PROGRESS SEQUENCE. Small Skull

 

demold 4 PROGRESS SEQUENCE. Small Skull

 The outer plaster breaks away quite readily from the inner precoat layer

demold 5 PROGRESS SEQUENCE. Small Skull

 

demold 6 PROGRESS SEQUENCE. Small Skull

 

demold 7 PROGRESS SEQUENCE. Small Skull

 

demold 8 PROGRESS SEQUENCE. Small Skull

 

 

demold 9 PROGRESS SEQUENCE. Small Skull

Cracks in the pre coated plaster cause ‘flashing’. Thin veils of glass bleed into the fracture making for more clean up time.

Can occur by numerous causes.  A couple of common ones are the wax expanding when warming up through the steaming out process and moulds too wet when placed in the kiln and the temperature ramped up too quickly causing the trapped moisture in the plaster to boil with no way to escape.

demold 10 PROGRESS SEQUENCE. Small Skull

 

demold 11 PROGRESS SEQUENCE. Small Skull

 

demold 12 PROGRESS SEQUENCE. Small Skull

Thin, fragile veils (flashing) of glass showing through the fractured plaster matrix.

demold 13 PROGRESS SEQUENCE. Small Skull

Final lifting off of the remaining plaster and a quick rinse under the hose…..  

dresssing fini PROGRESS SEQUENCE. Small Skull

Washed off plaster mold residue and now to cutting off the sprues and dressing. 

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DRESSING OFF THE CAST GLASS SKULLS

A selection of diamond tools and silicon carbide to finish these small Lead Crystal Skulls.

 

dresssing 11 PROGRESS SEQUENCE. Small Skull

Cutting off the Glass Sprue.

A 10 inch, sintered diamond, trim saw quickly cuts off the sprue.
dresssing 2 PROGRESS SEQUENCE. Small Skull

Diamond Cutting the Sprue

The water cooled diamond saw makes short work of removing the glass sprue on these small skulls.
dresssing 3 PROGRESS SEQUENCE. Small Skull

Sprue cut off the Skull

  The detached sprue to be recycled for a cast another day. The remaining stubb on the rear of the skull to now be dressed back .
dresssing 4 PROGRESS SEQUENCE. Small Skull

Mounted Diamond Wheel

A 7″ sintered diamond, 220 grit, grind wheel mounted on a point carver system.

 

dresssing 6 PROGRESS SEQUENCE. Small Skull

Initial Grinding on the Diamond Wheel.

Initial Grinding & Finishing 

dresssing 5 PROGRESS SEQUENCE. Small Skull

Wet Grinding on the Diamond Wheel

The Diamond Wheel is also run with water acting as coolant and lubricant.

dresssing 10 PROGRESS SEQUENCE. Small Skull

Micro-Motor Handpiece

A 50,000 rpm Micro-Motor hand-piece using a selection of diamond points to dress back ‘flashing’ and other imperfections on the surface of the Crystal Skull.
Note the ‘bubbles’ of glass in the eye sockets which have to be ground away.

dresssing 9 PROGRESS SEQUENCE. Small Skull

Hand tooling the Skull

Final Hand grinding of the skull prior to sanding and finishing.
Again water is the coolant and lubricant which is fed through the brass fitting to the work area on the surface of the glass. 

dresssing 7 PROGRESS SEQUENCE. Small Skull

Final dressing off of the Cast Skulls.

Final sanding performed on a 5″ inflatable drum sander mounted on the Point Carver system.

  

dresssing 8 PROGRESS SEQUENCE. Small Skull

Final Sanding

Steady pressure on 220 grit, wet & dry, silicon carbide belts remove the harsh diamond marks.
Notice the glass ‘bubbles’ in the eye cavity is still to be ground out.  

dresssing fini PROGRESS SEQUENCE. Small Skull

Finished!!

A small, hand held, Kiln Cast, Lead Crystal Skull finally finished.
The matt texturing from a light sandblasting imparts a deep glow.
blueboyfnt1 PROGRESS SEQUENCE. Small Skull

Blue Lead Crystal Skull

Many colors are these made in.