FAQ (Frequently Asked Questions)

This list of questions are some which are frequently asked in e-mail and on the forum. Hopefully this list will save time for everyone especially those just starting out in metalcasting. -June/20/2005

I'm new to metalcasting can you tell me what I need to do to get started?
Buy a good metalcasting book and read it. There is no "shortcut" to learning what you need to know. It is easy to learn but you need to still do your homework. There are several good books listed on the Metalworking bookstore page.

I'm new to metalcasting what type of furnace should I start with?
Melting metal is simple and if you are good at building things then you'll definitly have no trouble building a furnace. Most people say to start with a charcoal burning furnace (like the Flowerpot furnace I published a booklet about) because it is dead simple to use. But people who end up really enjoying metalcasting tend to advance toward a more convenient fuel such as propane. So they build a propane burner (similar to one described on my site) and a furnace similar to the "2-bucks" furnace detailed on my site. If you think you'll have a real interest in metal casting and you're willing to buy a propane tank and regulator, then just start with the propane furnace. If you're handy you should be able to buld a furnace and burner just from the information on the website. Making the actual sand molds is more challenging and i takes some practice but not too much. Get a book that describes the process and just get to it yourself. My sandcasting booklet is meant for complete beginners. But most importantly you have to actually practice the stuff on your own because that's when the real learning begins.

Can I use a propane burner without a regulator?
It is possible but is is not recommended. The pressures inside the propane tanks can raise to levels far to high for the safe use of the propen burner. The regulator keeps the pressure of the gas entering the burner at a safe level.

Can I use the small regulator that goes to my barbecue grill for my Oliver-upwind burner or other blowerless burner?
No, they don't release propane quickly enough. Look at the rigging a propane system page for details on the right regulator.

Will you build a burner for me? I have money.
I can't do that, not unless I get a lawyer to write up a water tight disclaimer for me to post on the site and have buyers sign. I will not build anything for you which is directly incontact with or creates heat, therefore I will not be responsibe for accidents which, unfortunetly sometimes happen.

Do I need a blower for my propane burner?
If the burner is designed to not use a blower then it doesn't need a blower.

How does the Ursutz derived burner work?
Both burners work on the same principal but the newer one on the homepage is shaped a bit differently to improve combustion and it has a better air/fuel intake system. The burner is basically just a sheetmetal box lined with the same type of refractory that the furnaces are lined with. The refractory is about 1" thick. The inner chamber of the burner is rectangular about 6" long and 4" wide. The rectangular shape seems better than a circular shape because it produces more air turbulance which speeds the combustion. On the newer burner; the "Organic lipid thermal energy reactor" (OLTER) the blower is connected to a seel pipe and the oil line feeds straight into the air line. It works similarly to the venturi on a lawnmover engine. There is no oil nozzle and the oil is not pressureized (the system uses gravity to carry the oil). A valve simply controls the speed at which the oil drizzles into the airstream which blows the oil into a semi-mist for easier ignition. The burner is started with a nice hot wood fire (sticks, etc) in the burner's inner chamber. After about 5 minutes of the oil burning the burner is so hot that the oil fire is self sustaining. The flame exit port is just a sheetmetal tube lined with refractory with a 1 or 1-1/4" diameter tunnel runing through it to carry the flame.

Why do some people suggest not using iron or steel crucibles?
After a awhile the iron or steel crucibles begin to erode and flake apart. The molton aluminum (or bronze, etc.) can absorb some of this iron which will weaken the castings on a molecular level. It's usually said that on the typical backyard hobby quality this is no problem and is not even noticeable. But when attempting to keep the metals as pure as possible (i.e. when making high quality ingots, special alloys, or structural/mechanical parts) a ceramic crucible is best.

Will you weld together a crucible for me? I have money also.
I can't do that for the same reason I won't sell or give away burners.

What do you make your crucibles out of?
Take a look at the building steel crucibles page.

Are there any substitutes for parting compound?
If you can obtain actual parting compound that is of course best but some substitutes that have been used by various hobbyists are; baking flour, talcum powder, baby powder and I've even heard of diatomacious Earth (from a gardening store) can be used. When using substitutes you may need to experiment because they may not work with certain molding sands (for example, it may work with oil bonded sand but not greensand) and they may be more sensitive to the moisute content of the sand.

Can I use a ceramics kiln as a foundry? I have one in the garage.
I've read about several people who have used ceramics kilns to melt metal. Some of them used electric kilns and as-is and it took about an hour for the electric element to heat the kiln to the melting temperature. Other people have modified the kilns with gas burners and that resulted in very large capacity furnaces. I'm only guessing here, but this type of kiln may also work well as a burn out oven for "lost wax" casting.

How much heat can your refractory formula withstand?
I have not conducted any tests to determine the limit of the refractories effectiveness. I can only say that it withstands the heat for melting aluminum very well. But like most homemade formulas, it doesn't withstand heat as well as good quality commercially prepared refractories.

Is homemade refractory as good as store bought refractory?
In general homemade refractory does not las as long as storebought refractory. Homemade mixes usually contain common materials like clay, cement, sand a garden store perlite. These materials make a refractory that works well at aluminum melting temperatures, but temperatures above that (like for bronze or iron melting) cause the mixture to break down and the sand content often turns to a glass like substance. Store bought refractories usually contain "exotic" components like alumia, calciaum sulfate and other heat resistant hard to find materials. These are far more duarable in the higher temperature ranges.

Should I use a store bought refractory rated to 2,600 or 3,000 degrees F.?
This depends on the metal you're melting. If you'll only be melting aluminum and occasionally bronze then 2,600 degree rated refractory is fine. If you'll be meting bronze or iron on a regular basis the higher temperature mix is prefered. The higher the temperature rating of the material the heavier and more dense it is. It also allows more heat to pass through it so the furnace shell gets hotter. Lower temperature refractories are less dense so they have more air spaces which provide better insulation. But they are more easily chipped if struck.

What is fireclay and where can I get it?
Fireclay is a powdered clay used if furnace refractory (the heat resistant lining) and molding sand. It provides most of the heat resistance in the formulas. I buy it from large masonry materials suppliers. If they sell clay chimney pipe they probably sell fireclay.

Is fireclay the same as furnace cement?
No. Furnace cement is a special heat resistant cenent which works like regular cement excenpt it resists a lot of heat. Fireclay is a component in some furnace cement.

What is bentonite clay and where can I get it?
Bentonite clay is just another type of powdered clay. It has more bonding strength (is stickier when wet) than fireclay. It is best used in molding sand formulas. The most popular sources for it as far as I know are pottery supply warehouses, some farm supply stores and well drilling outfits. A lot of people tell me they have trouble finding fireclay. I guess its just a matter of what part of the country you live in. Some people have used plain, fragrance free kitty litter which is made of bentonite clay. The only problem is that you'll probably have to grind it into a powder. Some people however get lucky and the kitty litter they obtain readily dissolves in water forming a smooth mush which can be dried out and used.

Can I use soda and/or beer cans as an aluminum source?
Yes you can but there is a "trick" to using them successfully. Since the cans are so thin they easily burn and oxidize rather than melt. For this reason many people say they should not be used. But if you already have a good pool of molton aluminum in the crucible then the can can be melted efficiently by crushing them (top to bottom) and dropping them into the pool. If the dry cans are pushed below the pool's surface they will melt and be less likely to oxidise. This aluminum is almost pure (unlike car cyclinder heads which are alloys). So the metal will usually shrink more when cast. but it is extream;ly shiny making it good for small decorative castings.

What are some good sources for scrap aluminum?
Potentially any aluminum obect could be a source. The best alloys for casting machine parts are old aluminum machine parts. Some examples are, car cylinder heads, transmission cases, water pump housings and pistons. This is a strong alloy which usually doesn't shrink much. More common sources are lawn chair frames, storm door and window frames, beverage cans, foil, disposible turkey and pie pans etc. The second group of aluminum sources are known as extruded aluminum (as opposed to cast aluminum) because of the way the products are manufactured. It's more of a pure aluminum so they are shiner when cast making them good for decorative castings. But they are weaker and the castings usually shrink more while cooling. Machining charactoristics are often not as good either.

Can I melt gold with the homemade equipment on your site?
The equipment and methods detailed on backyardmetalcasting.com are not designed for precious metals. Special crucibles are needed for these metals to keep losses to a minumum. The furnace may reach the proper temperature to melt the gold or silver but without a special crucible and other materials the metal losses from oxidation etc will be expensive.

Do you know of a place that sells ingots?
Try www.budgetcastingsupply.com

Can I melt iron in the flowerpot furnace?
Probably not. This furnace is designed to be simple and quick to build with low cost "everyday" items to get you introduced to metalcasting as fast as possible. It won't hold up to melting much more than aluminum and small amounts of bronze.

Will the homemade greensand work for iron casting?
It will work for iron casting but it is not the best for this purpose. The higher temperatures of molton iron will wear out the molding sand much quicker than aluminum will. This is caused by the clay in the mixture being vitrfied (like fireing pottery in a kiln) causing it to lose is bonding ability. Molding sand used for iron casting often uses different clays than the regular fireclay and often has powdered coal added to it which is said to improve the surface quality of the castings. Also the heat of the iron is more likely to turn the silica sand to glass.

I'm having trouble with the flowerpot furnace, it's build just as you describe
1) The crucible is too large (there should be at least 2.5 inches all around the crucible to fit a good amount of charcoal all around it). And there should be a good bed of charcoal under it.

2)The gap that you found between the flowerpot and the metalpot may have cause exces heat to escape since there wasn't insulation in there.

3)The metal you were melting. Try to melt a solid chunk of aluminum first. When you melt thin material like soda cans or eavestrough then sometimes the metal can oxidize before melting and form slag. But a chunk of aluminum with automatically form a molton pool of metal and then the thin material will safely melt in the pool creating less slag.