Lost wax casting?

[Kisu]

Having seen a number of knives recently (particularly Zeubest's "Christmas Knives") with cast fittings does anyone have any information on the process?Have done a search on the internet and can't find any practical help (without spending a fortune).

One other question - has anyone got any experience of working with siver clay? Is this a practical way of 'casting' fittings??

Any advice / information gratefully received.

[MushiSushi]

I can describe the process here briefly, but you would be best getting yourself a book like "Jewellery and Silversmithing Techniques" by Carles Codina, or something similar.

it is exactly as it sounds: Sculpt what you want to create in a sculpting wax, you then make a mould of it from a high temperature moulding material making sure you have created pour and breather holes. you then bake the mould to remove the wax and then pour in the molten silver, etc. let it cool and then break out the silver casting.

[Kane]

Googled and found these :-

http://www.ray-vin.com/casting/lostwax/lostwax1.shtml

http://www.borsheimarts.com/lessons/casting.htm

Google for "lost wax casting"

Kane

[Zeubest]

Kisu, I'm glad that my knives can be a part of your motivation.

Lost wax technique is very old and very simple. But, as any technique, there's some basis you'd better follow.

1) Wax

First, you'll have to make you wax :) The wax I use is the same used by dental technicians. I's a medium/hard wax, that can be heated for "adding" and carved for "removal"... You can find jewelers wax, very hard, made for carving in. The harder the wax is, better the details are (you can use candle wax, but you'll experience problems to make small details).

The material I use for wax is simple :

http://perso.wanadoo.fr/007/lames/cire/outils.jpg
A small alcohol lamp, used to heat spatulas, heated spatulas to make wax drops to build my fittings. :D
You can find this kind of materials on ebay.

Before building wax, I first " paint" my balde and my handle with a liquid to avoid the wax to stick to it (you can ask to a dental technician for it, ou use soap to wash the dish).
http://perso.wanadoo.fr/007/lames/cire/cire1.jpg

When my wax is ready
http://perso.wanadoo.fr/007/lames/cire/cire4.jpg

To transform this wax into metal, we now need to pour a refractory material around, then heat it to remove wax before pouring metal in this mold.
To pour the refractory, we use a rubber base with a cone in the middle, and a cylinder (inox)

I remove carelully my wax , and mount it on a wax "tree", on top of the rubber cone :
http://perso.wanadoo.fr/007/lames/cire/cire5.jpg
The main branch will bring metal to my fittings, the small branches, going from fittings to bottom are used to let hot air out of the mold, and to cool thick parts.

Check position in the cylinder , then pour it
http://perso.wanadoo.fr/007/lames/cire/cylindre.jpg

You can use, as casting investment, dental investment, jewelry investment, refractory plaster, even refractory concrete used to build barbecues ! Of course, special investments are giving the best surface results. Before pouring you can "paint" the wax with investment using a soft brush, to help it going in precise parts. During the pouring process, hit the side of the cylinder to help bubbles coming out.

Then, it goes in the furnace (electric furnace, home made (http://www.forgefr.com/forums/viewtopic.php?t=2408&start=0), you have a member of this forum that has made a nice one)
2 hours at 250°C, to let wax out, then up to 750°C to let investment "expand", then beck to the required temp according to your metal (550° for bronze).
The heating process depends on your investment material.

When this heating process is dont you can pour your metal.
To pour the metal , I use a spring machine I made (http://www.forgefr.com/forums/viewtopic.php?t=3434&start=0) :
http://perso.wanadoo.fr/007/lames/cire/coulee.jpg
When the temp of the cylinder is correct (550° here), I heat my metal, when the metal is almost ready, I take my cylinder from the furnace (on the right) to put it in the spring machine, and when the metal is liquid, i release the spring, it centrifugates the metal in the cylinder.
Cylinder cooling :
http://perso.wanadoo.fr/007/lames/cire/cylindre2.jpg

When cold, I remove the investment and cut the parts from the tree :
http://perso.wanadoo.fr/007/lames/cire/metal1.jpg
It's rough metal..I use a dremel to clean and adjust it :
http://perso.wanadoo.fr/007/lames/cire/metal2.jpg
Then polish it :
http://perso.wanadoo.fr/007/lames/cire/metal3.jpg
http://perso.wanadoo.fr/007/lames/cire/metal4.jpg
I can't help kidding: notice that the dragon wears a watch... :)

After that, process as usual :)

After this post was copied to the tutorial fourm, I added the following comments for kisu.
I copy it here :

Dear Kisu I've made it for you : :)

http://perso.wanadoo.fr/007/lames/cire/cireperdue.jpg

1 - Make Your Wax
2 - Make a "tree"
3 - Pour investment (shake the cylinder gently, hit it with a spatula)
4 - In furnace, let the wax out, then heat according to your investment and metal
5 - Pour your metal
6 - Approximative metal trajectory
7 - Let it cool (as Wayne said, I generally drop my cylinder in water after 1 or two minits, it removes quite all investment)
8 - Then you have your tree with parts to cut ( for "soft" metals, you can cut it using cutting pliers)
9 - Clean, adjust and polish... :)

Think of pouring metal as if you were pouring water : avoid places where bubbles can be kept (even if investment is a bit porous to gaz).

Consider too that metal will retract a bit while cooling, so, if you have thick parts add small branches to help it cool before incoming metal. If incoming metal is cool before your thick parts, you can have a porous metal at the junction points.

Also take care not to add too much boric acid while heating your metal, or you'll find it in your parts.

:)

[MushiSushi]

that's a very good tutorial Monsieur Zeu.

The parting agent is called Scopas parting agent, can be bought through Tiranti, but where to get it in Mombasa, I have no idea :D. ... believe it or not, you can actually use KY gel, paint it on and let it dry, then to release, just wet it again for a few minutes in the sink, this rehydrates the gel and you can remove the sculpt.


did anyone notice the socket on the wall inside the smelting area? hmmm

[Kisu]

Zeubest,

You are a star that is just what I needed - many thanks.

This is a great tutorial and might be better in that section??

Can you get away without centrifuging the molten metal?? If not, I will have to get my wife to try and translate from the link that you gave:D

Thanks again.

Kisu

[Kisu]

Googled and found these :-

http://www.ray-vin.com/casting/lostwax/lostwax1.shtml

http://www.borsheimarts.com/lessons/casting.htm

Google for "lost wax casting"

Kane

Thanks for these kane - the first one was particularly useful.

Cheers

[Zeubest]

Can you get away without centrifuging the molten metal??

You can, but you need big metal in to your parts, and big metal outs. It's less precise technique.
Vaccum techniques work well, but's harder to build something able to handle big cylinders..I'm building a machine to do it, should be working in january, I hope.

In Africa, it's done this way for traditionnal art (in French):
http://www.la-borne.com/fifta/

I've explained the way I do, but there's a lot of others (you can't centrifugate a 3 meters high bronze horse !) specially for bronze and aluminium :
http://www.backyardmetalcasting.com/


did anyone notice the socket on the wall inside the smelting area? hmmm
:) But , on the picture, you can't see the fat user watching carefully what's going on while heating, or the electrical differential 30 milliAmp on it. :D

[Wayne D]

When cold, I remove the investment and cut the parts from the tree :


This is the same method I use when making jewellery - If you use Casting/ Dental/ Jewellery investment, a tip given to me by the Master Jeweller who taught me ; when the metal has been cast wait until the mould has cooled enough that when you spit on the end metal 'button', it goes toffee coloured, then very carefully keeping the ends pointed away from you, slowly put the mold into a metal bucket of water (slide it in at an angle of about 45 degrees), the heated mold will react with the water and froth/ bubble as it cools which then causes it to break down and removes most of it from your casting .

This method can be used on very fine and delicate cast pieces to ensure that it's easy to remove from the mold without damaging them