Thanks for all that info. What size crucible would you recommend? I think ill use my devil forge gas forge but if that's too small then I'll make something bigger. also what do you know about using coal? it seems a bit easier than gas
Crucible size is relative.
I often use a #10, and some consider that size huge.
I have used a #30, and I have a friend who pours I think a #70.
The crucible size is roughly equal to the weight of molten aluminum it will hold, so a #10 will hold perhaps 10 lbs of aluminum (perhaps brim full), or about 3 times that for iron, or 30 lbs of iron.
Generally a brim full crucible is difficult to pour, and so you typically use a crucible that is perhaps 70-80% full.
I use Morgan Salamander Super clay graphite crucibles exclusively, and they can be purchased on ebay.
The Salamander Super can be used for any metal, but unlike most crucibles, it is ferrous-metal-rated, and also rated for iron temperatures.
I use a dedicated crucible for each metal type.
If the parts you intend to cast are small, then you could use a #5 or even smaller crucible.
It all depends on what size parts you intend to cast, with the understanding that you will need extra metal for the sprue, runners, gates, and any risers.
You can melt aluminum in a forge (a forge is sort of like a furnace laid on its side, with one end open).
No need to build a dedicated furnace if you just want to play around and melt a bit of aluminum.
The forges I have seen typically use a propane burner, but sometimes they are fitted with an oil burner.
For melting aluminum, a propane burner is sufficient.
Years ago, the trend was to put a crucible in a pit of charcoal, and burn the charcoal to melt the aluminum.
This method works, but is a bit tedious and time consuming compared to just using a propane burner.
I suppose you could burner coal around a crucible too, but I am not sure what that would do to the exterior of a crucible.
I have not seen anyone melt iron using charcoal or coal.
What I often see in the art-iron world is coke used to melt iron in a cupola.
Coke is coal heated in the absence of oxygen.
I originally though that burning coke in a cupola was a good way to melt iron, but then I tried to buy some coke, and could not find any for sale anywhere, unless I bought an entire truckload of coke.
A cupola is a large, messy, labor intensive affair.
An oil fired furnace will do the same thing that a cupola will do, but the oil furnace can be operated by one person easily.
A cupola can produce a considerable amount of molten iron once it gets started, simply by continuing to feed coke and scrap iron in the top.
Running a cupola to melt iron is a bit of an art.
I have seen it done, but have not tried it myself because I can't find a source for coke.
I have seen some fail at getting the cupola going, and had the iron solidify inside the cupola, which creates a big problem.
Even if I could find small amounts of coke now, I would not build a cupola, because they are just too difficult and messy to operate compared to an oil burner furnace.
If the only source of fuel I had was coal, then I may try it melting aluminum.
If you had a source for coke, you could melt iron.
I burn about 2.7 gallons per hour of diesel, and I don't do that many iron melts, and so using diesel is clean (compared to burning waste oil) and not too expensive for me.
If diesel prices go too high, I will consider burning waste oil, but would wear a powered respirator to avoid the fumes.
.
