Post by 1dave on Mar 24, 2016 19:21:01 GMT -5
An Extension of CASTING.
I mentioned Jay B. Bown way back in 2013 when I started the Casting and Fabrication Threads.
Yesterday I received a DVD from Jack Stamper of Merion VA that he made of JB at a rock show in Florida in 1993.
I knew that JB had traveled to rock shows all over Utah, Colorado, Arizona, and New Mexico, but didn't know he had made it as far east as Florida.
I've extracted some images from that video to illustrate some of his techniques.
JB in Florida 1993
JB lived in Orem UT in the 1970's when Indian Jewelry was in it's heyday. (We were buying silver for $3.00/Oz - scrap silver for half that.) Looking for easier work than his stone masonry, he studied with the Navajo silversmiths in Provo. There he experimented with sand casting. His experiments changed the course of his life. He discovered that somehow in the electromagnetic relm, Like carbon, garnet somehow prevents oxidation.
He invented the "Garnet Block" and his commercial artist wife, Lois, made his first brochure.
Casting sand requires a minor clay component to hold it together when dry.
You may find a different combination more to your liking. Crushed dunite as used in aluminum casting or olivine may serve better as the sand. Try varying the amount of clay.
4 to 1 = 25%, 5 to 1 = 20%, 6 to 1 = 16.7%, 7 to 1 = 14%, 8 to 1 = 12.5%.
Back to JB, his combination allowed him to wet the surface of his garnet blocks and re-work the sand-clay surface when it became marred. He liked to rub it smooth with sandpaper to remove contaminants.
This allowed him to carve patterns into his garnet blocks, melt scrap silver on them, melt the silver, then flatten the silver with the 3" block, then extract the cooled silver casting. He could then dump on the carved out material, wet the surface, work it back into a paste, smooth it out, and let it dry.
He was then ready to do it all over again.
I mentioned Jay B. Bown way back in 2013 when I started the Casting and Fabrication Threads.
Yesterday I received a DVD from Jack Stamper of Merion VA that he made of JB at a rock show in Florida in 1993.
I knew that JB had traveled to rock shows all over Utah, Colorado, Arizona, and New Mexico, but didn't know he had made it as far east as Florida.
I've extracted some images from that video to illustrate some of his techniques.
JB in Florida 1993
JB lived in Orem UT in the 1970's when Indian Jewelry was in it's heyday. (We were buying silver for $3.00/Oz - scrap silver for half that.) Looking for easier work than his stone masonry, he studied with the Navajo silversmiths in Provo. There he experimented with sand casting. His experiments changed the course of his life. He discovered that somehow in the electromagnetic relm, Like carbon, garnet somehow prevents oxidation.
He invented the "Garnet Block" and his commercial artist wife, Lois, made his first brochure.
Casting sand requires a minor clay component to hold it together when dry.
JB used 3 parts fine garnet sand to 1 part potter's clay.
Green sand (from Wikipedia)
These made of wet sand that is used to make the mold's shape. The name comes from the fact that wet sand is used in the molding process. Green sand is not green in color, but "green" in the sense that it is used in a wet state (akin to green wood). Unlike the name suggests, "green sand" is not a type of sand on its own, but is rather a mixture of:
1. silica sand (SiO2), chromite sand (FeCr2O4), or zircon sand (ZrSiO4), 75 to 85%, sometimes with a proportion of olivine, staurolite, or graphite.
2. bentonite (clay), 5 to 11%
{OR 25% ACTIVA Blackjack Clay (usually white) - special blend of several natural clays resulting a silky smooth consistency specially formulated for optimum pottery workability}
3. water, 2 to 4%
4. inert sludge 3 to 5%
(5.) anthracite (0 to 1%)
There are many recipes for the proportion of clay, but they all strike different balances between moldability, surface finish, and ability of the hot molten metal to degas. The coal, typically referred to in foundries as sea-coal, which is present at a ratio of less than 5%, partially combusts in the presence of the molten metal leading to offgassing of organic vapors.
Green sand for non-ferrous metals does not use coal additives since the CO created is not effective to prevent oxidation.
Green sand for aluminum typically uses olivine sand (a mixture of the minerals forsterite and fayalite which are made by crushing dunite rock).
The choice of sand has a lot to do with the temperature that the metal is poured. At the temperatures that copper and iron are poured, the clay gets inactivated by the heat in that the montmorillonite is converted to illite, which is a non-expanding clay.
Most foundries do not have the very expensive equipment to remove the burned out clay and substitute new clay, so instead, those that pour iron typically work with silica sand that is inexpensive compared to the other sands. As the clay is burned out, newly mixed sand is added and some of the old sand is discarded or recycled into other uses.
Silica is the least desirable of the sands since metamorphic grains of silica sand have a tendency to explode to form sub-micron sized particles when thermally shocked during pouring of the molds. These particles enter the air of the work area and can lead to silicosis in the workers. Iron foundries spend a considerable effort on aggressive dust collection to capture this fine silica. The sand also has the dimensional instability associated with the conversion of quartz from alpha quartz to beta quartz at 1250 degrees F.
Often additives such as wood flour are added to create a space for the grains to expand without deforming the mold.
Olivine, chromite, etc. are used because they do not have a phase conversion that causes rapid expansion of the grains, as well as offering greater density, which cools the metal faster and produces finer grain structures in the metal. Since they are not metamorphic minerals, they do not have the polycrystals found in silica, and subsequently do not form hazardous sub-micron sized particles.
These made of wet sand that is used to make the mold's shape. The name comes from the fact that wet sand is used in the molding process. Green sand is not green in color, but "green" in the sense that it is used in a wet state (akin to green wood). Unlike the name suggests, "green sand" is not a type of sand on its own, but is rather a mixture of:
1. silica sand (SiO2), chromite sand (FeCr2O4), or zircon sand (ZrSiO4), 75 to 85%, sometimes with a proportion of olivine, staurolite, or graphite.
2. bentonite (clay), 5 to 11%
{OR 25% ACTIVA Blackjack Clay (usually white) - special blend of several natural clays resulting a silky smooth consistency specially formulated for optimum pottery workability}
3. water, 2 to 4%
4. inert sludge 3 to 5%
(5.) anthracite (0 to 1%)
There are many recipes for the proportion of clay, but they all strike different balances between moldability, surface finish, and ability of the hot molten metal to degas. The coal, typically referred to in foundries as sea-coal, which is present at a ratio of less than 5%, partially combusts in the presence of the molten metal leading to offgassing of organic vapors.
Green sand for non-ferrous metals does not use coal additives since the CO created is not effective to prevent oxidation.
Green sand for aluminum typically uses olivine sand (a mixture of the minerals forsterite and fayalite which are made by crushing dunite rock).
The choice of sand has a lot to do with the temperature that the metal is poured. At the temperatures that copper and iron are poured, the clay gets inactivated by the heat in that the montmorillonite is converted to illite, which is a non-expanding clay.
Most foundries do not have the very expensive equipment to remove the burned out clay and substitute new clay, so instead, those that pour iron typically work with silica sand that is inexpensive compared to the other sands. As the clay is burned out, newly mixed sand is added and some of the old sand is discarded or recycled into other uses.
Silica is the least desirable of the sands since metamorphic grains of silica sand have a tendency to explode to form sub-micron sized particles when thermally shocked during pouring of the molds. These particles enter the air of the work area and can lead to silicosis in the workers. Iron foundries spend a considerable effort on aggressive dust collection to capture this fine silica. The sand also has the dimensional instability associated with the conversion of quartz from alpha quartz to beta quartz at 1250 degrees F.
Often additives such as wood flour are added to create a space for the grains to expand without deforming the mold.
Olivine, chromite, etc. are used because they do not have a phase conversion that causes rapid expansion of the grains, as well as offering greater density, which cools the metal faster and produces finer grain structures in the metal. Since they are not metamorphic minerals, they do not have the polycrystals found in silica, and subsequently do not form hazardous sub-micron sized particles.
You may find a different combination more to your liking. Crushed dunite as used in aluminum casting or olivine may serve better as the sand. Try varying the amount of clay.
4 to 1 = 25%, 5 to 1 = 20%, 6 to 1 = 16.7%, 7 to 1 = 14%, 8 to 1 = 12.5%.
Back to JB, his combination allowed him to wet the surface of his garnet blocks and re-work the sand-clay surface when it became marred. He liked to rub it smooth with sandpaper to remove contaminants.
This allowed him to carve patterns into his garnet blocks, melt scrap silver on them, melt the silver, then flatten the silver with the 3" block, then extract the cooled silver casting. He could then dump on the carved out material, wet the surface, work it back into a paste, smooth it out, and let it dry.
He was then ready to do it all over again.