Jump to content
MDF

Lost wax...failure

Recommended Posts

Hi Marco,

 

I just found this thread. Just in case you're still reading this, I've got some tips. I've got years of experience in bronze age style bronze casting. The problem with bad castings is always in the mould material. When you pour hot metal in the mould, anything that can burn, evaporate etc. will ruin the quality of your casting. If the mould material is totally inert, it should be possible to get details as fine as finger prints (depending on the coarseness of the mould material of course). Chalk which you used first is totally unsuitable. It releases CO2 when it gets hot, which ruins your casting. Clay can work brilliantly, but it depends on the purity how you need to treat it. If you have a very pure clay, you may get away by just heating it briefly up to red hot, and then cooling it. If the clay is impure (lots of lime etc. in it), it needs to be fired at at least red hot for at least 4-5 hours for small moulds (thickness up to around 1-2cm), or even longer for large ones (thickness >2cm). Mind that with clay you always need to mix it, or it will explode when heated. Even then it needs to be heated slowly (1-2 hours to bring it up to temperature for small moulds, really small moulds could be quicker). The mixes are a whole study in itself, but generally include lots of sand, and organic material (best traditional material is horse dung! :) ) for the outside of the mould, with a thin layer of fine clay (with only fine sand, or charcoal dust) to coat the waxes. N.b. you don't need flux. Just a small piece of charcoal floating on the surface is enough to keep the bronze clean. N.b.2 be very careful with what you melt. Preferably use a pure copper/tin mixture, which is the least toxic. Zinc, lead, beryllium etc. which can occur in unknown bronzes can kill you either instantly or eventually! Also don't breath too much CO, not very healthy in the long run either.

Share this post


Link to post
Share on other sites

Thanks for infos Jeroen,

 

I will continue to try, sooner or later I will get. This work is very frustrating :angry:

Share this post


Link to post
Share on other sites
Thanks for infos Jeroen,

 

I will continue to try, sooner or later I will get. This work is very frustrating :angry:

Heh, patience! :) I've been doing this for four years continiously, and still have plenty of failures (doing it fully the bronze age way makes it infinately harder). B.t.w. if you just want the product, go for casting sand (bindol). That's really easy to work with, and gives brilliant results. See the early medieval fibulae f.e. here, which I cast in casting sand.

Share this post


Link to post
Share on other sites

I just did a cast in silver last night, got a piece that needs to go out soon, so no time to order Satin Cast... so what I ended up doing was a very thin wash of plaster of paris, followed by a solid bed of satanite, on the piece to be cast (and sprues, and cup, etc). Then I put that into my flask with plain plaster around it, did the burnout, and used the tuna-can steam casting technique and got a nearly perfect piece. A little messy where my wax was very thin (under 1 mm) and it is clear that the satanite moved a little when the wax got hot (in the future, a full drying day before investing is ideal, I think) but for a "need it now" casting, it wasn't half bad, and I'll use it in my piece.

 

Pictures tonight, maybe.

Share this post


Link to post
Share on other sites

Chris if you need it I always have 100lbs of investment here. I could send you down a couple lbs. There is a good jewelry supply store near you that stocks it in 25lb boxes in Silver Spring. Thats often where I buy my 100lb barrels

 

Todays insanity is glass casting..... I had a burned out mold from another project (skull pommels!)so we broke up a bunch of glass rod and have it firing in the kiln. If it turns out I'll post a thread on the process. I've never heard of anyone vacumm assisting glass casting before, but I cant imagine it hasnt been done!

 

I'd have to agree that 99% of casting failures are mold related. If the mold is clean and hot enough (but not too hot!) stuff usually turns out.

Share this post


Link to post
Share on other sites

A 34 pound box of SatinCast is on my shopping list, but where is this place in Silver Spring?

Share this post


Link to post
Share on other sites
Get rid of the iron crucible,spend the $15 for a real crucible.also you can read the info on this link,it is 6 parts and may give you more insight. flux is your friend when casting most non ferrous metals.

 

Casting Basics

 

 

I just wanted to point out that that is an awesome tutorial for simple steam casting. The same tutorial can be found here with pictures displayed on the pages, care of Don Norris and Joe Hildreth.

 

Joe has a bunch of useful information up on his site about casting and machine tools.

 

-Joe Green

Share this post


Link to post
Share on other sites

I finally understood the problem :lol: the bronze gush outside the mold because they were not sufficiently burned. In recent experiments I inserted the moulds in my forge (used for hours) for an entire night. The moulds now working perfectly, no more gush, poured is perfect!

After a few months finally the most big problem is solved ... now remain 2 other problems: rounded edges (but now not always) and dark surface <_<

 

IMG_0017.jpg IMG_0019.jpg

 

For the rounded edges now the results are much better because the moulds not develop more gas but it is difficult to get well. The next time I try as suggested by Archie Zietman but i am thinking of made a simple vacuum machine, it's possible? someone has done? -0.9 bar are sufficiently?

 

The dark surface is a strange effect, first with the same material mould the bronze was clean, now is dark.

Share this post


Link to post
Share on other sites

I am building a vacuum casting machine right now.

 

I have all of the flanges made, and the pump is in my garage, I just have to weld it all together.

 

I will put together a tutorial.

 

Mike Lambiase

Share this post


Link to post
Share on other sites

Cool, Mike

 

Where did you find the pump? I've wondered about the difficulty of building a vacuum casting system for some time.

 

I'd love to see the pictures.

 

Josh

 

I am building a vacuum casting machine right now.

 

I have all of the flanges made, and the pump is in my garage, I just have to weld it all together.

 

I will put together a tutorial.

 

Mike Lambiase

Share this post


Link to post
Share on other sites

I am useing an HVAC repairmans pump.

 

all of them pull close to a perfect vacuum, so you just have to get one that moves the most cfm for your money.

 

or you can run tandem pumps and eveacuate the combined cfm.

 

The pump I have right now moves 6 cfm. I dont know if that will be enough, but the other casting machines I have seen (smaller comercial units) can move as little as 3 cfm.

 

I am building it so that I can have a bubble on one side to vacuum the investment, and stabilize handle material, and a 5 1\2" x 10" casting chamber on the other side.

 

I am waiting on a few more parts, so I can determine the dimentions of the machine before i start putting it together.

 

I think I have thrown down just under $400 in parts so far.

 

I need to be able to stabilize some horn for an order I am working on, so this machine is first thing on my list.

 

Mike Lambiase

Share this post


Link to post
Share on other sites
I am building a vacuum casting machine right now.

 

I have all of the flanges made, and the pump is in my garage, I just have to weld it all together.

 

I will put together a tutorial.

 

Mike Lambiase

 

Great Mike,

your next tutorial will be very useful for me.

Thanks

Share this post


Link to post
Share on other sites

I started making a simply vacuum machine for bronze casting: a section of pipe with 2 openings (vacuum and pressure gauge).

Now I have to build a perforated flask.

What do you think about this?Can work?Soon I hope to finish this and try it

 

IMG_0085.jpg IMG_0088.jpg

Share this post


Link to post
Share on other sites

This looks similar in design to the casting chamber part of what I am going to be building.

 

I am waiting on a peice of 5.5" pipe from one of my friends that works in a pipe shop.

 

I have everything else ready to put together.

 

My tutorial is coming....

 

Mike Lambiase

Share this post


Link to post
Share on other sites

Well, finally my vacuum machine is over :rolleyes:

I tried it yesterday and the maximum vacuum is -0.92 bar, reached in a few seconds.

Now I have made a new model and test it ... i hope this time is good!!

What do you think of it? I have never seen a vacuum machine and I built this just by looking at some photographs.

 

IMG_0090.jpg IMG_0093.jpg IMG_0094.jpg

 

IMG_0095.jpg IMG_0096.jpg

 

IMG_0097.jpg

Share this post


Link to post
Share on other sites

Hi guys,

I am very happy, finally I managed to get a good result.

The vacuum machine it's good! this is my first encouraging result.

All the old problems have disappeared (no more rounded edges), now remains only one problem, my sand investement is crumbly and collapses in the corners whit vacuum machine.

I believe that with a professional investement I solve this problem

 

However I believe to be on track

 

thanks at all for the support :lol:

 

IMG_0171.jpg IMG_0170.jpg

 

IMG_0166.jpg IMG_0165.jpg

 

IMG_0164.jpg

Share this post


Link to post
Share on other sites

After a long wait between wrongs and experiments the big day finally arrived!

This is my last result, every detail has been copied by the new professional investement and the vacuum machine is perfect!

The Thor hammer is perfectly clean exit from the mould.

Now finally I can making bronze guards for my daggers and knives.

 

Thank guys for the valuable information. :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

 

IMG_0179.jpg IMG_0178.jpg IMG_0176.jpg

 

IMG_0175.jpg

Share this post


Link to post
Share on other sites

Watching you make this journey has been a great learning experience. There is no substitute for making one's own mistakes, but seeing an honest account of another's trial and error is the next best thing. Thank you for documenting your experience so well, and sharing all of your setbacks, as well as your triumphs.

 

I admire your ingenuity, as well as your determination. Congratulations!!

 

Luke

Share this post


Link to post
Share on other sites
Watching you make this journey has been a great learning experience. There is no substitute for making one's own mistakes, but seeing an honest account of another's trial and error is the next best thing. Thank you for documenting your experience so well, and sharing all of your setbacks, as well as your triumphs.

 

I admire your ingenuity, as well as your determination. Congratulations!!

 

Luke

 

 

Thank you very much Luke,

I am very glad of your words.

This was a great experience for me and...more fatigue more happiness :lol:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...