I've been interested in metal casting almost as long as I've been interested in blacksmithing.   I've been
reviewing several casting websites (mostly in the hobby foundry web ring).  I've come to a few conclusions.
1) Most everyone is basically reinventing the wheel.  
2) Everyone is spending way too much money on this
3) Melting aluminum is pretty easy with propane.  Brass and bronze is slightly difficult (it takes a little while
to get the scrap or ingots to melt).  Copper does require a lot of heat and can be difficult but is very doable
in a propane forge.  


Let's just start with those.
1-         
The most salient argument I've read against making "exotic" burners is this: do you want to be a metal caster
or do you want to be a burner designer?   The latter is frustrating and time consuming. When you finally
have something that works, it's generally anticlimactic and the end result is dastardly close to a design that's
known to work. This is the process I went through in building my first six forge burners.

The sites that truly make me concerned for the hopeful metal caster would have you make your own venturi
burner using common pipe fittings and drill bits.  Venturis are notoriously difficult to tune and without
exception require high PSI to run. I've not seen one that's designed to run hot enough for metal that requires
less than 6PSI, most are between 10-30PSI.  The Northwest Blacksmith Association (NWBA) uses only
venturis at conferences.  Every one of them is tweaked several times during demos and hands-on classes.  
Some of them burn "cold" regardless of how much tweaking is done, others burn hot.  A commercial venturi
will seem expensive compared to off the shelf plumbing parts, but if you insist on not using a blower, I
really recommend spending the extra money.  If you're an experienced machinist then the above may not
apply to you.  The main (only?) advantage to venturi burners is that they require no electricity to run.

Don Fogg has the simplest propane burner imaginable and it can get hot enough to forge weld  steel with
relatively little propane.  He uses a simple blower and feeds the propane into a pipe that becomes the
burner.     
  
Waste oil and charcoal are, in my opinion, more trouble than they're worth for casting and for most
smithing, for that matter.  There is satisfaction in using ancient methods to work metal, so charcoal and coal
aren't entirely out of the question.  Solid fuel forges and furnaces require a lot of fuel  and in my neck of the
woods, no solid fuel is even remotely "reasonably" priced.  Charcoal that is suitable for metal work (natural
softwood like the Japanese use) is very hard to find. You'll end up settling for hardwood (mesquite usually)
that pops, cracks, sends hot embers all over and leaves a lot of ash.  I
watched in horror the fireworks
display as burning embers waft across t
he yard and landed on the least opportune thing you can think of-
t
he roof, the patio furniture, dry grass and even in my hair.  Softwoods are preferred as they have more
BTU by weight and less ash but it's very hard to find softwood charcoal and it burns up very quickly.  
Waste oil is generally messy- it's oil.  You have to store it.  It spills.  It stinks. It smokes all over the place
until you get the burner and foundry up to working temperature
and then it smokes when the forge is
turned off.
 Even hybrid propane/oil burners are reportedly a pain in the keister.  That's not to say I won't
give a hybrid a try, but it's not on my list of priorities.


2-
Efficiency is key.  B
ringing your forge or foundry furnace to temp quickly is vital for efficiency.  The most
common foundry furnace is the large tub that has about 80# of homemade castable refractory in it with
another 20# as a lid.  Yikes!  
Homemade refractories are notoriously slipshod.  Professional companies make these to industry
specifications in easy-to-use formats (generally dry, mix like cement.)  Every one of the homemade
refractory recipes I've seen costs more per pound than commercial refractories (like Mizzou).  But worst of
all, they're costing you money in terms of wasted fuel and time.   It takes a lot of heat to b
ring 100# of
castable refractory up to melting temperatures.  That's what's required before the heat starts to soak into
your crucible and metal.  My experience using castable for a forge lining keeps me away from these heavy
heat sinks.  
A better solution is refractory blankets that are coated with heat reflective ceramics.  My preferred are
Superwool and ITC-100.  Yes, these are seemingly expensive, especially the ITC.  But consider that I can t
ake
my forge up to bronze melting temp in under 10 minutes at less than 4 PSI of propane.  A fully open propane
tank with a BBQ style regulator at 10PSI is what I've seen recommended by several sites... you can't argue
with the fuel savings of the lighter, more reflective materials compared to the furnace that takes over a half
hour to get to aluminum melting temps.  In the long run I'm using more of the heat for melting metal and
I'm d
oing more in the same amount of time.  I don't need to devote an entire Saturday to casting, I could do
it before dinner is ready, after work on a weeknight.

3-
Getting your first melt is an accomplishment.  But consider- you may have just spent a bunch of money on
heavy refractory, a dolly setup to move your furnace and a lifting mechanism to open the lid.  Then it took
almost a half hour to get your furnace up to 1400F and you've almost used up an entire BBQ size propane
tank (which anymore costs about $22 to fill.)   Again, I can get to bronze melting temperatures in approx 10
minutes.  I can make pattern welded steel in my forge in about 20 minutes (which requires temps almost
double that of aluminum.)  Below I've outlined my setup and why I have it set up the way I do.  

Feel free to disagree.  I encourage open, respectful discourse.  But do keep in mind that anything sent to an
alchemyforge.net or .com email address is fair game to be published on this site or in my blog... unedited ;)
Really, any blower will do.  This one
happens to put out 150 Cubic Feet per
Minute (CFM).  The little white square
is a piece of cardboard that I use as a
choke and I'm probably running
20CFM on average.  What you can't
see is the 90deg elbow fitting because
the choke is blocking it.

The black hose with the brass fittings
is the propane inlet.  You'll note that
it's near the outlet of the blower.  This
helps with the air/fuel mixing.  I've
put the propane in the 90deg bend,
after the bend and this is the place
where I'm getting the most heat for
the least propane.  Air/Fuel mix.  
Engine tuners know what I'm talking
about.

Length isn't vital, but having the step
down in the end runner (small rusty
pipe fed by the shiny pipe) does help
with gas velocity.

There is not a step at the end.  The
pipe is 1.25" all the way.  I adjust the
choke so the flame always propagates
at or near the end of the tube.  If the
flame is basically only visible as it
bounces off of the far wall, you're
using too much air.  If the flame looks
limp and greenish, you're not using
enough air.
Forge body: A popcorn tin lined with superwool and coated with ITC100.  The bottom is
lined with wood ash, crushed firebrickand then topped with sairset kiln mortar.  The
purpose of all of these items is to keep heat in the burn chamber (not in the forge shell or the
refractory and certainly not in the environment).  The large firebricks are used to keep the
heat in as well.  They are moved, as needed, to accommodate larger pieces.
And this is how I have it set up for everyday use.  A small crucible goes in the front, fits
nicely and gets good heat all around.  The front bricks are brought together to keep as
much heat in as possible.  

I've also modified my acetylene welding set to use propane (instead of acetylene) and
oxygen.  With this I can get bronze and copper to puddle very readily.  I make my own
crucibles out of pottery clay and finely cut grass.  I bake them and then fire them in my
forge at near welding temp- the crucibles get white hot.  I let the crucible cool in the forge
by simply turning off the gas.

I've been steam casting using instructions from this site:
http://users.frii.com/dnorris/steamcast1.html  There's a total of six pages.

I'll post some results here and you'll see the work in finished pieces.
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