PAPER NO 2 ANTI FIRE SCALE PROCESS SIMPLE METHOD

October 14, 2010
BY
LEE EPPERSON

Fire scale has been the scourge of sterling silver casters since the first silver was poured into a mold. It has been a thorn in the side of silver fabricators. Fortunately there are ways to prevent fire scale while silver soldering.

This paper describes a simple, inexpensive method of preventing fire scale during vacuum casting.

Fire scale is cuprous oxide, the combination of copper in the silver or gold with oxygen. Fire scale forms whenever silver or gold containing copper is heated above 1000 degrees F. Unlike cupric oxide, the black coating on silver, fire scale cannot be removed in the pickle pot. Normally it is removed by abrasion, electro striping or left as a surface finish.

Fire scale usually shows up, as a purple or copper stain in the metal, during the polishing process. It prevents sterling silver or gold from being polished to its fine, brilliant luster.

The method of preventing fire scale during the casting process consists of preventing oxygen from reaching the metal while it is cooled in the investment mold. The use of a reducing flame and graphite crucible during the melting process will help in keeping oxygen from the metal as it is melted. Oxygen must be removed during the cooling process in order to prevent fire scale.

By accident I found a way to prevent fire scale during vacuum casting. I can now produce sculptures in sterling without worrying about how to get rid of fire scale. It is my impression that fire scale forms as long as the sterling is above around 1000 degrees.

Fire scale is forming as long as the sprue button is red. Therefore fire scale is forming during most of the time the metal sits in the mold before
quenching

This is a sample of a regular sterling silver casting that was cooled in the reducing atmosphere created by the process described in this paper.

The casting was quenched seven minutes after the pour. It was brushed with a brass brush to remove the investment. Investment can still be seen under the bear. The casting was not pickled and does not need to be pickled before polishing it. It is free of both cupric oxide, the black oxide, and cuprous oxide, fire scale.


The method described in this paper to prevent the forming of fire scale during the cooling process is very simple. It allows the metal to cool in a reducing atmosphere.

Castings, when removed from the mold, are bright silver. They do not have to be pickled to remove the black coat. In some instances they can be polish with jewelers rouge after removal from the quench water.

The process requires two smooth soldering pads, scrap wax shavings and an empty flask the next size larger than the mold flask.

I place some wax shavings on a solder pad before I start the pouring. Once the metal is poured I place the mold flask on the wax covered solder pad.

I then place the larger flash around the mold flask.

Wax is then thrown on the sprue button and the second solder pad is immediately placed on top of the cover flask.

The wax inside the cover flask absorbs the oxygen as it attempts to burn.

The flask should be cooled for a longer period of time then normal as the heat does not dissipate as rapidly because of the cover flask.

When the flask is first quenched the wax forms seals with the investment and prevents it from breaking up. The flask has to be removed from the water and the surface of the investment scrape to remove the wax/investment skin. The flask is then quenched as normal.

FIRESCALE PREVENTION

STEP ONE

Place about a tablespoon of wax shavings on a solder pad prior to pouring the metal.

STEP TWO

Place the hot mold flask on the wax shavings on the solder pad. The wax will immediately melt and seal the bottom of the flask to the solder pad, which prevents air from entering the investment mold and metal from the bottom side.

STEP THREE

Place the cover flask around the mold flask. The wax will seal the cover flask to the solder pad.

STEP FOUR

Throw wax shavings on the sprue button.

STEP FIVE

Place a soldering pad on the cover flask. The wax shavings will attempt to burn and will absorb all the oxygen around the mold flask and the metal it contains. A reducing atmosphere will be created around the mold flask. There will be no oxygen remaining in the cover flask to combine with the copper in the sterling silver to form firescale.

STEP SIX

Quench the flask in cold water. The cooling water will cause the scrap wax to form a bond with the investment when it hits the water. The flask should be quenched for a few seconds then removed from the water. A sharp tool should be used to break open the investment on both ends. The quenching cycle should then be continued.
The cooling of the casting flask will take longer due to the fact it is enclosed in the cover flask. The cooling time before quench should be increased by a minute for small castings to several minutes for larger castings.

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PAPER NO 2 ANTI FIRE SCALE PROCESS SIMPLE METHOD

October 14, 2010

BYLEE EPPERSON Fire scale has been the scourge of sterling silver casters since the first silver was poured into a mold. It has been a thorn in the side of silver fabricators. Fortunately there are ways to prevent fire scale while silver sold…

Read the full article →

PAPER NO 2 IMPROVED ANTI FIRE SCALE VACUUM CASTING PROCEDURE

October 13, 2010

ByLEE EPPERSONleessilver@cox.net602-993-4766This paper describes a process that eliminated fire scale during a vacuum casting cycle. Castings should not have a fire scale problem if the casting are cooled following this procedure.This casting was coole…

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PAPER NO 2 IMPROVED ANTI FIRE SCALE VACUUM CASTING PROCEDURE

October 13, 2010

ByLEE EPPERSONleessilver@cox.net602-993-4766This paper describes a process that eliminated fire scale during a vacuum casting cycle. Castings should not have a fire scale problem if the casting are cooled following this procedure.This casting was coole…

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PAPER NO 12 TEXTURES IN WAX

October 13, 2010

ByLEE EPPERSON This paper will describe and show various textures that I produce in wax and on the finished silver. WAVE TEXTURE This texture is produced with a hand made tool mounted in a cable driven hand piece. I do not have a pictur…

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PAPER NO 12 TEXTURES IN WAX

October 13, 2010

ByLEE EPPERSON This paper will describe and show various textures that I produce in wax and on the finished silver. WAVE TEXTURE This texture is produced with a hand made tool mounted in a cable driven hand piece. I do not have a pictur…

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PAPER NO 7 WAX CONSTRUCTION PROJECT

October 13, 2010
By
Lee Epperson
CONSTRUCTION METHOD

In the construction method of making a model various pieces of wax are shaped then the pieces are wax welded to other pieces to form the model. The construction model may be made from any combination of sheet, wire and carving wax.


This paper will describe the construction of a buckle as shown in the photograph.


The size of the buckle will be determined by the maximum size of the belt it will be mounted on.


The width of the buckle where the loop is mounted must be slightly wider that the belt loop.


A loop of 10 gauge wire is bent around the center of the loop. Its function is to center narrow belts on the buckle.
The findings will be soldered to the cast buckle.


A piece of 16 gauge sheet wax must be cut out to the basic shape of the desired buckle.
The shape of the buckle is drawn on a card or similar piece of stiff paper. The shape is then cut out.


The shape is then drawn on the 16 gaga wax sheet by a pointed tool which is moved around the border of the cardboard shape.


If the shape is to be used many times a plastic template may be created.
The plastic shape of the buckle can be cut out with a jeweler saw. The edge of the plastic should be smoothed with a file. Lines were inscribed on the plastic to act as guides for some buckle designs.


A knife is used to cut the buckle from the wax sheet.

A buckle has a slight curve to fit the body. The curve may be formed by bending the sheet over a curved surface.


A piece of wood may be carved with the necessary buckle curve. This is recommended if many buckles are to be made. The wood acts as a support for the sheet wax.
The sheet wax is formed over the curve on the wood. Spot weld the sheet to the wood. Note the tack welds on the corners.


The design calls for mounting three turquoise stones on the buckle. The edges of all the stone cabs are cut at a slight angle. In metal fabrication work the bezel is formed to fit the larger dimension of the stone. The stone is then placed in the bezel on top of a compressible material. The bezel is then pressed against the stone which is pressed against the compressible material.

This works fine for pieces constructed from metal with thin gage bezels.
The edges of stones, used in a casting with a heavy bezel, must be ground so that the edge is vertical to the back of the stone. The bezel will not be pressed against the stone.


A silicone carbide cut off disc mounted in a hand piece may be used to grind the edges perpendicular to the base of the stone.
A diamond file may also be used to cut the edge.

Several 1/8 inch strips are cut from the 16 gauge sheet wax. The knife will cause the edge to swell slightly slightly when the cut is made so it is best to cut the strips from the original edge of the sheet wax.

Cross section of the wax bezel:


The bezel strip of wax is bent around the stone. The process is similar to the process of forming a metal bezel. The wax is cut so that the bezel fits the stone.


The wax joint is wax welded. Any excess wax should be cut away.


The stones are temporally located where the design dictates. It is recommended to leave the stones in the bezel. Be sure the edge of the stone is exposed above the bezel so it can be removed from the bezel.


Wax weld the inside and outside of the bezel to the base.


Wax rods of various diameters will be added to the base. 1/8 inch, 1/4 inch, and 8 and 10 gauge wax wires will be added to the base. A jig is set up to insure all the rods are cut to the same length, which is equal to the height of the bezel.
The color of the waxes is insignificant as various wax vendor color their waxes differently,


A hole is drilled thorough the center of the ¼ inch wire. Coral dots will be inlaid in these holes once the buckle is cast.


The pieces are wax welded to the base. The pieces are slightly sticky and will stick to the tip of a tool. The tool is used to locate the piece before it is welded to the base.


Once all the wire pieces are added to the base the background is textures. A spatula tool is used to paste sticky wax to the background. The tool is slightly heated before it picks up some sticky wax. The surface of the sticky wax may be smoothed or left rough depending on what type of surface is desired.

Sprues are added to the buckle and the sprues are wax welded to a flask base.


Add a wax fillet to all joints.

The buckle is cast. Once cast the sprues are removed and the portion of the sprues remaining on the buckle are ground flush with the buckle.

The back of the buckle is polished with tripoli the wiped clean with alcohol to remove oils and grit.

Several lines are marked on the back of the buckle with a Sharpie felt pen.

The entire piece is covered with Cupronil then the buckle findings are soldered to the back of the buckle.


The buckle is mounted on two fire bricks so that the torch can be played on the back surface. The buckle is heated from the underside until the pen marks disappear.


Once the pen marks disappear the torch is played on the joint of the belt loop and buckle. The loop is wire soldered to the buckle. The keeper is soldered to the loop.


The buckle is oxidized.


The bezel and rods are sanded with wet 600 grit sandpaper.


The inside of the bezels are roughed up with a burr. The inside lower edge of the bezel is undercut slightly. The undercut will provide a lock for the epoxy used to hold the stone in the bezel.


Branch coral is ground to a round shape to fit into the smaller bezels.


A dab of instant glue is placed on the coral once it fit’s the bezel. The coral is then placed in the bezel.


The coral is cut with a diamond saw close to the top of the bezel. Coral has a tendency to break into the bezel. To prevent this the coral should be slightly cut on one side then cut on the other side. The coral is then ground and sanded flush with the silver.


The stones are touched up with a diamond wheel till they fit the bezel. The stones have to be marked to match the bezel they will fit into.


Epoxy is mixed and placed in the bezel and on the back of the stone. Place any remaining epoxy aside. It can be checked later to test its cure.


The stone is then pushed lightly into the bezel. Epoxy will be forced out of the bezel. The excess epoxy should be scraped away with a screwdriver or similar tool. Continue to press the stone into the bezel and clean up the epoxy until the stone is set properly.


Once the stones are set in the bezel the remaining epoxy on the bezel and stone may be removed with a bristle brush mounted in a cable driven hand piece. The stone and bezel should be slightly whetted.

An abrasive wheel mounted in the hand piece may be used to remove any epoxy after it has cured on top of the bezel.

The buckle is then polished using normal jewelry polishing techniques.

The polishing compound that is embedded in the recesses may be removed with soap, a tooth brush and water. Crest sells a battery powered toothbrush that has both a rotary and oscillating section. It works very well in removing polishing compound.

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PAPER NO 7 WAX CONSTRUCTION PROJECT

October 13, 2010

ByLee EppersonCONSTRUCTION METHODIn the construction method of making a model various pieces of wax are shaped then the pieces are wax welded to other pieces to form the model. The construction model may be made from any combination of sheet, wire an…

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PAPER NO 3 MODIFYING DENTAL TOOLS FOR WAX CARVING

October 13, 2010
By
Lee Epperson
leessilver@aol.com

Line incising tool


The basic dental tool used to engrave wax is called a “Woodson.” One end of the unmodified Woodson tool is shown at the top of the photograph. The end is modified to look like the tool at the bottom of the photograph. This end of the tool will be used to incise the design into the wax.


The dental tool is cut and ground as this photo indicates.


The tool may be modified with a silicone carbide separating disc mounted on a mandrill mounted in a flexble shaft driven hand piece.


This tool is used to cut a line in the wax which follows the design. The photo on the left shows the angle the tool is held against the was. The photo on the right shows a curl of wax the is cut out by the tool.

Line engraving tool

The other end of the Woodson tool is modified to look like the tool in the bottom of the photograph. This tool will be used to engrave the line in the wax.


The dental tool is cut and ground as this photo indicates.

Care must be taken to grind the base of the triangle perpendicular to the shaft of the tool. If it is ground at an angle, the tool will have a tendency to track incorrectly.


These two photos show how the tool is held and the angle of the tool to the wax.

Background engraving tool

Another Woodson tool is modified as shown above. This tool will be used to scrape away the wax from the background of the design.


The background is pulled at an angle to the engraved line. This will insure the tool does not break out of the area of wax to be removed.

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PAPER NO 3 MODIFYING DENTAL TOOLS FOR WAX CARVING

October 13, 2010

ByLee Eppersonleessilver@aol.comLine incising toolThe basic dental tool used to engrave wax is called a “Woodson.” One end of the unmodified Woodson tool is shown at the top of the photograph. The end is modified to look like the tool at the bot…

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