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This Instructable will cover the general process I followed to cast an aluminum (or aluminium) bowl, a replica of a glass kitchen bowl. This is the story of scrap aluminum, melted to a complete liquid, and remade into something awesomely new. My guide will not go into great detail as to the construction of the furnace, the molding flasks, or the crucible tools. See more about these in the Requisites section.

Before we begin, I'd like to throw in the necessary word on safety. Safety isn't always fun or exciting, but the hospital is less so. Don't pour molten aluminum or slag onto concrete as this will create violent (really - these are forceful) exlosions that will propel molten or just-solidified chunks of aluminum many yards into the air and sideways. I know from personal experience. Also, wear safety glasses, boots, and jeans. These are great for those insignificant but annoying cinders that make little burns. Alright - enough "safety" talk, let's get melting!

Step 1: Requisites

If I were to explain everything I did to make the aluminum bowl, this Instructable would be 70 pages long. Thus, is is prudent to list off some things that you will need as basics to this casting project. Here we go:

  • The Furnace: Arguably the most important part, save for the aluminum to melt, the furnace will melt your metal and hold the fuel's heat in. This can be (with lower performance) as simple as a paint can with a hole near the bottom of the side to blow air into through a pipe. Mine, however, is party helium tank cut at the top, lined with 2" of a refractory cement made of fire clay and sand. It has a 2" steel pipe coming in near the bottom of the side to supply extra air to the combustion of charcoal in the tank. The cut-off lid has a hole in the top for the exhaust. Find more info about this at:
  • The greensand: Another important part of the casting process, this is the material which you will shape into your mold to pour the metal into. Mine is a 12:100 ratio mix of powdered cat litter and sifted play sand, by weight, moistened a small amount. Find more info on the greensand at:
  • The crucible and tools: These are what you melt and handle the aluminum with. The crucible can be as simple as an empty camping size propane tank with the top cut off, but I have had some bad experiences with this type of crucible becoming holey and dropping aluminum into the furnace. I used a clay-graphite crucible from http://www.budgetcastingsupply.com/. You will also need tools to handle the crucible with. If you are using a metal can like the propane cylinder, a pair of long pliers will work fine. If you use a real crucible, I recommend building 2 pairs of tongs, one to lift with and one to pour with, from 1/4" steel stock. This is what I did, with the assistance of a friend.
  • The flasks: The containment for the sand, the cope (upper) and drag (lower) molding flask boxes are used to provide firm walls to ram the sand into and against. I made mine as 5"x9x"x9" plywood boxes (no top or bottom) with holes in blocks on the sides for dowels to slide into. These dowels provide alignment to make sure that the sand molds line up right each time. This site has some decent info on building your own flasks: http://www.penguinslab.com/furnace4.htm
<p>I have cast plenty on aluminium in my day, it is always a fun time... Nothing better than working with Molten Metals :)</p>
It is ridiculously fun! I love seeing the super shiny liquid aluminum streaming from the crucible.
<p>Same here :)</p>
<p>Congratulations, very good work.</p>
Thank you! I enjoyed the casting process.
<p>Did you borax your aluminum right before the pour, or was that something else you poured on top?</p>
<p>He says what it was in this stament here:</p><p> &quot;Next, pour 1 tbsp. each of washing soda and table salt onto the liquid metal. These act as degassing and fluxing agents, respectively, removing bubbles and slag from the melt.&quot;</p>
<p>You can avoid that dimply/wavy bit on the bottom of your bowl if you put a sprue/gate to catch the initial dumping of aluminum. The sprue/gate will then be dimply/wavy and your casting nearly perfect (as far as those surface imperfections). You also don't need as many risers. With the gate off set from center of the bottom of the bowl, you can put one riser on the opposite side of the bottom. You only have one, flat point to clean up (the bottom) instead of 9 points around the bowl. Does that make sense or am I just muddying up the waters?</p>
No, I think that makes sense. I would have done something like that, except that the bowl was sort of large and I only made the cope and drag big enough to fit the bowl, not a gate going off to the side. Thank you for the absolutely great advice, though!
<p>Very nice! </p>
Thank you! I really enjoyed the process of making the bowl.

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