Let's Get Started
After the burn out time of about two hours it is time to cast, but during that two hours we should get everything ready for this process.
But first--a word about torches. I am teaching this Online Class for those who would like to do casting at home with as little cost a possible. This is why I am using the inexpensive propane torch that you can usually purchase from Ace Hardware for about $10.00. The type of torch that you use will have the most impact on the success of your castings than any other part of Steam Casting. A better kiln would be nice, but it really will not affect your success that much. The torch you use however, will determine how fast you can melt your metal, and how much you can melt quickly enough to cast. Your success will be determined by how hot the flask is, and how quickly you can get the metal into the mold before it cools. If it is too cool, the metal will freeze as it enters the sprue wires, and the cooler temperature of the surface of the investment cools the metal enough to solidify it before it fills the mold.
Therefore, if you have an acetylene torch such as a "Prestolite,"
or even better, a "Smith Handiheat,". It is the torch that I like the best for silversmithing. They will melt your metal faster and increase your success rate greatly. Even an oxy-acytelene torch can be used, though I usually do not like to use oxygen to melt silver. It will cause more firescale, oxidization and pits in your casting.
The small propane torch will work, but every thing has to been done as directed if you want to get 100% success rate in your casting. So start with this torch, and make enough money to purchase the Smith torch. As I said, it is the torch that I use for silversmithing and silvercasting, and I always recommend it to my silversmithing and silvercasting students.
Step One: Get the caster ready.
Soak the paper towels in the caster, and squeeze the excess water out by pressing the caster down on top of a soup can.
Step 2: Get ready to cast.
Safely Note: Make sure your fire extinguisher is charged. To do this, take a plastic cup, fill it with water, and keep it handy. Also, you should wear goggles or eye protection. (Actually, I recommend an that you prepare to cast doing the following: Put on an athletic cup, knee pads, elbow pads, back brace, lifting belt and body armor. Then cover all this and yourself with tin foil, especially the top of your head. Then put on one of those fire fighters suits [you know the ones that used to made of asbestos until we found that it hunts us down and attacks us.] Put in ear plugs, followed by those ear protector muffs, and a helmet. Protect your hands with welding gloves and put on steel-toed shoes. Put on light filter glasses followed by goggles. Be sure to put on the best air filtering mask that you can find and hook an oxygen mask to that. Be very careful with the oxygen; we are going to use a torch you know. Oh, the tin foil is so that you can't be detected by aliens as you cast. They are always trying to steal this technology.) Final warning: if you do something stupid, you can injure yourself, burn down your house, your neighbor's house, kill the dog, and/or start a small world war. There, I think I have now covered my tail as far as safety. I sure hope so! Proceed at your own risk!
Cover your table with something that will not burn easily. Plywood, particle board, or any thin metal will be fine.
Place some borax (another tuna can is good for this)
an old brick or any other porous surface, torch
a lighter on the table, and your charged fire extinguisher.
Step 3: Preheat your metal.
Measure out your metal. You want enough to cast the piece, plus enough to leave a large sprue button in the crucible (sprue button formed by the mound of wax). You want this extra metal for the following reasons:
- I always want the sprue button to be larger than the casting because I want it to be the last thing to cool. I want the casting to cool first. This will allow for any shrinkage problems. As the casting cools, it can draw metal from the larger still molten sprue button. I learned that this is very important when I did a lot of sand casting. I found that large reservoirs of metal decreased the shrinkage in the piece being poured.
- A large sprue button will aid in the metal being forced into the mold. It gives the force that every method of casting must use, something to push against. Therefore, the more metal there is, the more force to push the metal into the mold at a pressure that will decrease porosity. Some people recommend building reservoirs between the sprue button and the wax pattern. This is completely unnecessary if you have a large sprue button. In fact this secondary reservoir can increase porosity by increasing the surface area the silver flows over before entering the mold, and by increasing the turbulence of the metal within the mold.
I preheat the metal so that it will take less time to melt it on top of the flask. This will increase your chances of a good cast because it will give the flask less time to cool down. This will help with the problem of the metal cooling as it is forced into the mold, and as it is cooled by the lower temperature of the investment.
Place your silver or other metal in a small depression carved out of the top of the 2 x 4.
An old charcoal block or soft fire brick is great for this step! (these are available from the Rio Grande Co.)
Put on your gloves.
Melt the silver with the torch. If you have not lit a torch before, or are a little afraid of it, please follow these instructions:
First let me show you how to ignite a lighter correctly for starting the torch. Hold the lighter so that your thumb rolls the striking wheel to the side of the thumb.
Do not use the tip of your thumb. This will hurt your thumb, and it may touch the hot metal part of the lighter while lighting the torch. Ouch!
Lighting the torch is easy if you do it right. Do it wrong and it scares you, your neighbor, and your teacher! Follow these steps and you will never be afraid of lighting a torch again.
- Light the lighter.
- Place the lit lighter directly under the torch's tip.
- Slowly turn on the torch--very slowly. If you do not know which way to turn the knob to turn on the torch, follow these instructions: Without trying to light the torch, turn the knob both directions, until you can hear the gas come out. Do this several times until you know which way to turn it on. No, it will not fill the room with gas and blow you up, and no, it will not gas you and kill you. The whole tank could empty in to an average room and not blow up or gas you. It will, however, stink. Now, back to the steps.
- While you are turning the torch on with the lighter under the nozzle, a small fluffy flame will appear first. Leave the lighter on, and keep turning on the torch slowly, until this small fluffy flames "jumps" down into the torch and comes back up as a sharp, short flame. The torch is now lit. The next step is to adjust it to flame about 1 1/2 inch long.
- When the metal is melted and forms a puddle, quickly take the torch off the metal, and sprinkle a little borax on to the puddle.
- Quickly reheat the metal and melt it back into a puddle.
Now is when you must go into high gear and move with quick, concise movements. You may even want to practice this part when everything is cold, before you ever turn on the kiln.
Take the torch off the metal, and set it so that it can safely be kept burning, or have someone hold it for you. The metal will cool and solidify into a red hot button.
Step 4: Using the gloves or the tongs, get ready to take off the flower pot.
Step 6: Take off the flower pot.
Step 7: Quickly take the flask off the stove, and turn it over on to the brick.
Step 8: Set down the tongs and use the tweezers to place the red hot button of metal into the sprue button, which is now going to act as the crucible.
Place the metal button on the side of the sprue button so that as the metal melts it will run down into the center of the flask.
I do this so that the metal heats faster and you can direct the flame at the metal that has not melted, while keeping the flask hot with the torch.
Step 9: Keep heating the metal and the investment continuously until the metal is completely melted and is pooled together in a bright puddle.
Step 10: As you heat the metal with your left hand (if you are right handed, right hand if you are left handed), grab the caster with your right hand and get ready to cast!
Step 11: Take the torch off the flask and at the same time place the caster firmly over the flask.
You want to do this very quickly and carefully. It needs to come down straight on to the flask. Hold the caster in place for about five seconds or so. Actually the metal is cast in the first split second that the damp towels touch the hot investment and the steam is created.
A small prayer is OK as you wait.
A note about safety: The reason I use a tuna can is that it is deep enough to prevent molten metal from splattering out. As it goes down on the flask the deep sides of the tuna can go down over the sides of the flask. If any metal were to spray out, it would just drop to the side of the flask and on to the brick. No problems!
Step 12: Take the caster off the flask.
Some of the metal should be gone! Wait about five minutes for the metal to cool.
Step 13: While you are waiting, get a bucket or some relatively large container and fill it with water.
Step 14: Take the tongs and carefully grab the flask in the middle.
Step 15: Put the flask completely under the water and "swish" it back and forth.
Do not move it top to bottom in the water, or the casting may fall into the bucket. This is not the worse thing you could do though. It just means you will have to go fishing for it in the bucket! I move it side to side carefully. The water will break up the investment and leave the casting in the flask.
You now have your steam casting.
Step 16: Clean and polish it as you would any piece of jewelry.
If enough people would like a quick class on cleaning and polishing castings, let me know, and I will do another section on a cheap and easy way to finish your castings.