Lost Wax Tutorial

Hey all,

I'm looking to get back into my coin casting project, and am looking for some advice. I've had some success with sand casting, but I think lost wax is the "correct" process due to the very fine details.

Does anyone have a resource for getting started with lost wax? Tutorials, equipment, materials, etc. I've got my propane furnace and sand casting equipment, but it sounds like lost wax requires a whole slew of other things (burnout kiln, investment, etc.). Any help is greatly appreciated.

 

Have you considered Delft Clay sand casting for higher detail?
Amazon.com: Delft Clay Original Casting Sand Kit Gold Silver Pewter Aluminum -Set Includes Ring & DVD

 

I made a few threads of the process. You'll have to scroll through to see the pics step by step.

http://forums.thehomefoundry.org/index.php?threads/eagle-statue-zapins.187/

http://forums.thehomefoundry.org/index.php?threads/octopus-sculpture.566/

 

Thanks! I've seen both of those threads and it's some really stunning work. Far, far too advanced for me though, lol. Perhaps I should have elaborated on my project. I know I've posted this before, but it must have been on AA so it's gone now.

I have a coin I'm trying to make copies of in something golden-colored, like silicon bronze. It's quite thin and the details on it are very fine:


I had pretty good success with regular sand casting, but it's tough. The lettering, especially. I figured lost wax would be better - make a silicone mold of the coin, create several wax copies, tree them up, invest, burn out, and cast. But those general terms are about all I know. What type of wax to use? What kind of investment? How does the investing process work? Do you really need a vacuum chamber to de-bubble the investment? Do you really need a kiln for burnout? And that's just off the top of my head; I KNOW there will be unknown unknowns down the line. So that's why I'm looking for just a basic tutorial or overview, just to get started at least. Advice on what equipment and materials I'll actually need for basic lost wax casting would be appreciated, too.

 

I agree with David. Solid advice.

For investment I used gold silk investment from SRS. Its jewelry grade investment. Pretty cheap too.

Spin casting using a centrifugal caster or vacuum casting is probably the way to go on these coins.

Tin cured silicone rubber is cheaper than platinum based. You can order it from many places. There are different kinds as well. Some are formulated to be very runny and are used for block molding and others are used to brush on. Both can be thickened with something called thixotropic. You can probably get by using either type of silicone but block molding might be easier since you don't need to key up the mold or make a 2 part mold.

If you don't vacuum your liquid silicone rubber it will have bubbles in it. Liquid rubber silicone needs to be vacuumed. The brush on type does not. But the brush on type is used to make 2 part molds because it sticks somewhat to parts.

The investment material usually molds well without vacuuming but vibration does help a lot.

 

Thank you all for the detailed responses. Really I'm trying to determine if solid block lost wax casting is something I can get into without spending an exorbitant amount of money. I just have the one project, after all.
It seems like a burnout kiln, vacuum chamber, and wax injector are the main pieces of equipment. The kiln would be the most cost-prohibitive. All I've got is my propane furnace, so hours-long burnout schedules won't really work with that.
I guess wax, flasks, investment material, and silicone mold-making liquid are the other necessary items.

Apparently I looked into this a while back and did actually make a silicone mold of the coin, using some two-part Smooth-On silicone. I also have some green Ferris file-a-wax. But that's as far as I got. Not sure if the wax will flow into all the tiny details without an injector, but I guess I won't know until I try.

 

Don't even think about using the Ferris file-a-wax.. It's not meant to be melted and used as a liquid. When melted and cooled it's very brittle. But guess what, it's really good for carving.

 

I have had very good luck with investment casting for fine details. See Avatar at the left for example. I made a Smooth On "near clear" silicone mold. You do need a vacuum chamber and having a pressure pot helps too. But you can make copy after copy at near perfect (ss good as your mold is) performance with this method. A good vacuum pump from eBay is a great investment for a lot of project. See is anyone is selling a Kiln on Craig's List in your area. I made my burn out oven from scratch but there are some smaller ones for same using a PID temperature controller on eBay too.

 

I got a smaller controlled kiln for $260 from ebay. And a centrifugal caster for round $130. These orchid flowers were made by investing two flowers and burning them out then spin casing.

 

A pressure cooker can be used as a vacuum vessel to invest in... You don't need to see the investment rise and fall.. You could even use plaster to practice with.. A few uses will teach you how you need to use it.. A vacuum pump could be used to invest, and by building a small vacuum table, used for casting... You can get by using a furnace if you can candle it low enough to get past the steam stage.. No direct flame, you don't need to burn out at high temps enough to make the investment white.. Without a lot of money, you gotta improvise or give up.. Try a pawn shop vacuum pump, it doesn't need to be a big pump, just that it works.. For a direct pull, an inline fuel filter would be a good idea in case the flask fails.. Start out with the most basic , and improve if you need to. I'm not sure what temp the silicone rubber on the vacuum table will take.. Or what temps a bronze flask needs at casting.. You could even try using a soup can that has a bottom you can cut out.. The ones with a pull tab top.. They have a reenforced rim to use as the bottom.
In your position these are a few of the things I think would work for you..

 

This book was a great resource when i started.
Lost-Wax Casting: Old, New, and Inexpensive Methods by Fred R. Sias Jr.
it confirmed i was at least on the right track. i did not have the money for any equipment or supplies in the beginning so i would try anything i though would work. like steam pressure. a great alternative if you dont have any vacuum of centrifuge.
you can do many things without specialized equipment if your expectations are in line with your efforts... one thing i will say that makes the process realistic is buying commercial grade investment. you will here plenty of suggestions and i would think they are all worth buying. i use prestige optima myself.

 

Zapins: so you straight invested actual orchid flowers? That's incredible! I'm amazed they stayed intact and the petals didn't get all bent up. Do you have a thread on that somewhere?

Thanks for the book recommendation, bill.

I should probably resign myself to getting the necessary equipment. I am looking for professional, repeatable results after all. There are other projects I could use the vacuum chamber and temperature-controlled kiln for, too, so that helps a bit.

 

Yes I invested the orchid flower. Was pretty easy I tried it on several different flowers and surprisingly it didn't collapse them at all. Even very fragile ones. Also seems possible to cast very thin objects. I got several hairs caught in one mold and it cast them into silver and some of the flowers were paper thin and still cast without voids.

I had pics of the process on alloyavenue but the site died and the links are dead. Here are some photos of an aquarium plant I cast into silver for an April fool's prank on my aquarium forum a few years back. Process is the same.

I used silk investment and spin cast them then used my magnetic polisher to polish all the tiny spots. It polishes without erasing fine details like veins. I have pics of that on another forum I can copy over if you want to see that machine build.

 

If you're looking for a good book on lost wax casting, "Bronze Casting Manual" by Olivier O. Duhamel covers all the basics. You can get it for about £20 on Amazon.

For wax, I use Investment wax. Not very good for sculpting with but it's great for pouring into moulds. For repairs and touch ups to wax copies, I'd recommend Ferris Red Patching Wax.