Casting With Delft Clay (White Bronze Anvil Pendant)

Intro: Casting With Delft Clay (White Bronze Anvil Pendant)

Delft clay casting is just one of many methods to cast metal objects. Delft clay casting has some drawbacks but is arguably the most accessible casting medium for those who are just starting out.

STEP 1: Create Your Form

One of major drawbacks to using Delft clay, or other casting sands, is that you can't cast an object with undercuts in a typical two part mold. luckily for me, I wanted to cast an anvil which doesn't have any undercuts from the side. The blue anvil about was hand carved out of medium density carving wax. The material of the model being cast is important because it's going to have to withstand a considerable amount of pressure. let's say that your favorite carving or sculpting medium is something soft like very soft wax or marshmallow, then before you proceed to the next step you would need to cast a hard resin version of it first. Once you have a tough object that you think is worth casting, then you may proceed to the next step.

STEP 2: Gather Your Supplies

Before getting ready to cast, you should have a casting frame. You can buy casting kits that come with tiny aluminum frames. My project wouldn't fit, so I decided to build my own. For this project, I didn't have my welder handy so I had to build one out of wood. However you decide to make it, it needs to be two flat forms that can somehow lock together. In my case, the locking mechanism was just some bent steel that kept the two pieces from shifting. Before creating the mold please save yourself some trouble later and put down a tarp or some plastic. Delft clay is just a pain to clean up, especially if you step in it. Delft clay is also reusable so being able to save as much of it as possible would be ideal because delft clay is expensive.

STEP 3: First Half of the Mold

Take one frame and pack it with the delft clay. I don't just mean fill the frame, I mean take something like a mallet and pound it until you basically have a solid brick within the frame that can hold its shape. The frame should be overflowing with with compacted clay, take a straight edge and cut the clay level with the frame. Once you have leveled clay, take your model and press it into the clay in such a way that you could later pull it out without disturbing the clay. The biggest part of the model should be toward where the pour point of the frame to allow for a cleaner pour.

STEP 4: Second Half of the Mold

Once you have the model in the first frame, you need to cover it in powder. The powder endures that the two halves won't stick together. The finer the powder the better, though in a pinch you can use all sorts of powder. In this instance, I didn't have any talcum powder, though I did have a charcoal block that I scraped over the first frame. With the powder applied, lock in the second frame over the first, and pack more clay into it before leveling it.

STEP 5: Remove the Form and Carve Channel

Carefully pry the two halves apart and carefully remove the model. With a sharp craft knife, carve a channel for the metal to travel from the opening of the frame to the cavity. Do this so that both halves match up and create an unobstructed funnel into the cavity.

STEP 6: Create Vent Holes and Connect Them to the Form

In order to prevent air pockets from forming in the final product you will need to carve vents. Take a sharpened dowel or a straw and poke several holes into one of the mold halves. Angle the holes so that the ultimately point upwards. This will keep the metal from all pouring out of the vents. with the holes places, carve tiny chanels from the model cavity to the vents so that the air can escape.

STEP 7: Put the Mold Together

This step is pretty self explanatory. Put the two halves together to that everything matches up and locks together.

STEP 8: Melt and Pour the Metal

Once again, pretty self explanatory. Put on all of your safety gear, set up your metal melting apparatus of choice and melt the metal. Be sure to add borax or some other flux to the metal to keep it clean and flowing consistently. Once everything is liquid then pour the metal into the channel and pray to your diety of choice that it worked. If you use far more metal than you need to, like I did, then some might come out of the vents. While a bit of spillage is a bit dangerous and a pain to remove, it doesn't mean that the rest of the cast didn't fill completely.

STEP 9: Remove the Solid Product

Once everything has cooled down, pry the two halves apart and remove the product. The product at this stage will be pretty ugly with flashing and vent spouts poking out from every direction. The next stage is removing all of that and clean up the form. You will notice that some of the clay in the two mold halves has turned black. Remove the blackened clay before reusing the clay because it will dilute the clay overall and make it less cohesive.

STEP 10: Cleaning Up the Product

Cut off all of the flashing, grind everything flush, and polish up the product. I realized that I didn't design a finding in the wax model, so I ground one out of the sprue metal that was attached instead of just cutting it right off.

STEP 11: Final Touches

I wanted to make the white bronze look more like weathered steel so I oxydized it. I also gave it a couple coats of renaissance wax so that the oxides won't rub off onto clothing and skin when it's worn. Thanks for reading!

Comments

[bdanielpa2019]

Hi. I'm pretty new to delft clay casting. I make my models out of sculpey clay.
2 problems I'm having:
1: sometimes the clay sticks to the model in the fine details (small letters, curves, etc)
2: takes SEVERAL attempts to get a good pour to fill the mold. I'm making several air holes and a pretty good size pour gate/channel.
Any advice? Thanks

[Armeria Garcia]

I don’t know about your
access to supplies, or the level of detail in your projects, but I might have
some ideas. One would be to make a silicone mold of the project first, and cast
it in either wax or plastic before moving to the delft clay. I did that with a
project before because the original model was far too weak and sticky for the delft clay. The
other alternative would be to put a very thin layer of glossy paint or varnish
over the model. I don’t use sculpey clay, so I don’t know about its surface
texture or how sand sticks to it. The other thing to be sure of is that the
sand is adequately tamped down before pressing the model in.


For the pours, I don’t know
what you are casting with, but once again I might have some ideas. Adequate heat
for your metal is probably most important, it needs to not only be molten, but hot
enough to make it to the bottom of the mold. Another thing that might help is
flux. I use borax for just about everything, but for whatever you are casting
it might not be right. Along with that, is skimming the top of the molten metal
to make sure that nothing is getting in the way or blocking the flow of metal.


Hopefully this helps. Thanks
for your question.

[bdanielpa2019]

Hi Armeria

Thanks for the reply
Here's some more info:
I'm casting mostly in .925 silver. Sometimes brass

I've been using MAPP gas canister by itself. It seems to take a long time to melt the silver. Maybe not getting hot enough? I know I don't have much time to pour as some of the silver cools in the crucible during the pour (and I always heat the pour channel of the crucible and keep the heat on during the pour) I also use borax a couple of time during each melt.

I tried Acetylene/oxy but it leaves a thick black layer on top. I'm thinking of trying propane/oxy.

I always make silicone mold of my model, but if I need a new model I use the sculpey clay. Can I melt the same kind of wax you used to make the anvil? would I melt it into the silicone Mold?

[Armeria Garcia]

Oxy/propane would probably help. In the instructable, I used oxy/acetylene, but now I just throw the crucible in the forge.

Personally i wouldn't try to melt the blue wax in the instructable unless you have the proper equipment. I don't have said equipment, so all of my attempts to do so have been mediocre at best. A two part resin would probably be best, and hold up to the sand a bit better.

Hope that helps!

[ninthRing]

An excellent tutorial on casting with Delft clay. It's fascinating to realise just how little has changed, with some techniques virtually identical to those used by artisans during the Bronze Age.

I'm a sculptor who has had some artworks cast in bronze, though admittedly with limited personal experience in making the negative moulds (with the hard work usually done by the foundry). Mostly so that they can set the standards they want & streamline production. (I reckon it's also so they don't have to spend too much time 'round artists.)

I just thought that I'd point out there's an important factor that you need to consider when casting with metals - they expand when hot and contract when cold (& each metal/alloy has it's own unique properties).

Comprehension of this is essential for two parts of the process:

Firstly when calculating the volume of metal that you're going to need for both the item you're casting and the pour channel / sprues, etc. Any mistakes at this stage could prove to be very expensive if you're using precious/semi-precious metals - compounded when upscaling your production to an industrial scale (imagine 10, 20, 100 little anvils getting cast in a huge pour.)

You also have to take the shrinkage of the metal into account when making the pouring channel [seen as a wide cone shape in your casting, here] & sprues. The industrial technique that I'm familiar with uses solid wax rods for sprues (they melt away during the pour, leaving channels in the sand for the molten metal to travel along & for any air to escape) and a cup shaped reservoir (of somewhat redundant metal) at the top. All of which works excellently to prevent cavities forming in your product.

[jshelton8]

Hello, I've been looking around different ways of making rings, charms etc.

Could the mould also be made from plaster Paris with a wax model and melted out in an oven before pouring say pewter?

[DaMidas]

Instead of white bronze, can I use aluminum that I melted down from soda cans?

[Armeria Garcia]

Aluminum should work just fine. Good luck!

[DaMidas]

Thank you.

[Gorilla22]

Instead of delft clay, could I use play-dough? It packs and can harden if you leave it for long enough. (I don't want to buy delft clay.)

[Armeria Garcia]

I would seriously advise you to not pour molten metal onto play dough. The point of using sand or other casting investments is that they can withstand lots of heat. Play dough, on the other hand, is made with flour which would most likely not fair well against something like molten bronze or silver. If you look through the comments, somebody provided a link to buy petrobond which is essentially the same as delft clay but much less expensive. Hopefully this helps. Thanks for the comment.

[kkinney]

Pardon my ignorace, but you apply powder to keep your mold material from sticking together. Why is that a bad thing?
Wouldn't it reduce the amount of flashing you need to remove?

[Armeria Garcia]

If the two halves of the mold stick together, then it will rip itself apart when you try to remove the wax model from the two halves. Unlike other casting media, you aren't supposed to burn out your wax model before casting. Flashing, in the case of sand casting, is a fairly common occurrence and is usually easier to cleanup than the metal in the vents. Hopefully this clears up that aspect of the casting. Thanks for the comment.

[ArcticShip]

A newbie question. Where did you get the white bronze?

[Armeria Garcia]

https://www.riogrande.com/Product/casters-white-bronze-chunks/706013

I hope that this helps!

[heimerdinger]

Really great instructable. :)

You're right though, delft clay is a little pricey (for my budget at least). Can you recommend anything cheaper?

[Armeria Garcia]

You should try looking into green sand recipes online. Most of them are much cheaper per volume than delft clay. The only downside being that you will have to mix it yourself and search for the right components. Some recipes are as simple as kitty litter (bentonite clay), fine sand and water. I hope that this helps. Thanks for the Comment.

[heimerdinger]

It's helpful, thanks for the tip :)

[lazemaple]

I tried green sand recipes, couldn't get the same detail Petrobond for sale here and well worth someone else doing all the mixing

http://shop.petrobondforsale.com/Mulled-Petrobond_c2.htm

[lazemaple]

Petrobond its virtually the same as delft clay - I've worked with both. 10 pounds for $30 I believe I paid http://shop.petrobondforsale.com