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I have melted and cast many parts from brass. The biggest problem is keeping the zinc in suspension during the melt and pour. To prevent the zinc from burning off, I used brown glass broken into small pieces mixed in with the brass to be melted. Be sure you use enough to cover the melt on top to prevent air from reaching the liquid. The liquid glass acts as a flux and as a seal to prevent burning the zinc. It is best to melt brass in an enclosed "furnace" rather than trying to heat with a single flame source. As far as using a steel or iron pot, we didn't have much luck with that. The best thing to use is a graphite crucible. The brass will not stick to it like it will with a ferous pot. You might have better luck with the iron pot however. It is worth a try anyway. For a mold you can also use styrofoam for a pattern. Make a sprue and riser from styrofoam and Crazy Glue them to the pattern. Set the entire assembley onto a bed of DRY sand and pour the remaining sand over the pattern to finish the mold. Leave about an inch or more of the styrofoam sprue and riser above the top of the sand. Tamp the sand down by hand to firm it up a little. CAREFULLY spray a mist of water around the sprue and riser to firm up the sand and prevent it from crumbling into the molten metal as you make the pour. Pressing gentley with your fingers to shape the area into a "funnel" is a good idea also. Make absolutley sure there is no water on the protruding styrofoam sprue and riser as this will cause a steam explosion when it is hit with molten brass. Let the area dry for a while or warm it with a hair dryer to remove all the moisture from the styrofoam. As you pour the brass, the gas given off by the vaporising styrofoam will keep the dry sand from collasping into the cavity were the patern is. Pour until the sprue and riser are completely filled. Let cool and remove from sand. Try using a styrofoam coffee cup and making a practice pour. Use aluminum for learning the process because it works much easier than the brass. After you get the hang of this you will be LOOKING for things to cast!
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