Feb 10, 20225 min read

Minor: planning & making

I've decided on submitting a bronze Laputan robot for my minor. I will need to outsource the bronze casting process as AUB doesn't provide these facilities. I found that Castel Fine Art Foundry offers a 'free wax scheme' which involves them sending you 240g of wax to make a sculpture with. Once I've completed the wax sculpt I will send it back for them to cast in bronze for £125.

It can take the foundry up to 12 weeks to cast my sculpture in bronze and send it back to me. Which gives me two weeks to make my sculpture. I'm already cutting it close as I received the wax on the 8th Feb giving me up until the 21st. Our hand in is on the 20th May giving me just over 11 weeks to submit the finished piece.

There are a few ways you can go about bronze casting. All share the same principal steps of replacing wax with bronze which is known as the lost wax process, but depending on the size or complexity of the sculpture, the steps to this will also vary in complexity.

There are mainly 4 departments to the bronze casting process.

Mould Making

Image: 1

Mould making is the first step to bronze casting. A mould of the artwork is made consisting of two or more parts depending on the size and complexity of the art work. Large artworks will require a jacket mould making the skin of the mould silicon, meaning less parts are needed due to its flexibility. On the other hand smaller artworks will use a hard plaster or jesmonite mould which usually requires more than two parts.

Lost Wax

Image: 2

The lost wax process is the second most complex step to bronze casting, and the department that I find most interesting. The steps to this process will go into more detail later in this blog post but for now a brief overview.

With the mould made of the original artwork a hollow wax shell is casted from it. Wax channels and a pour spout for the molten bronze to flow through are attached. The wax sculpture is then dipped into a vat of liquid ceramic and then sand, repeated until the shell is half an inch in thickness. The top of the wax pour spout is kept exposed. Finally the wax inside its shell is melted away leaving just the ceramic shell.

Metal Work

Image: 3

Molten bronze at 1800 F is poured into the ceramic shell and left to cool. The shell is then broken away using hammers, chisels and sand blasting. Any seam lines, locaters, imperfections and channels are grinded, tig welded, chiselled or filed away leaving no trace of them being there. Once the bronze artwork is all that's left its ready for a patina.

Patination

Image: 4. phot I took

Metal patinas are made through chemical reactions. In college I use ammonia and salt on copper and brass to achieve this blue patina. I found that foundry's use a more controlled method of applying patinas. They start by heating up the bronze sculpture in the areas that the patina will be applied. Then adding the chemical with a brush instantly making a patina. This is repeated until the desired effect is reached. To protect the patina and bronze surface itself a thin layer of clear wax is applied at the end.

I have to complete the sculpture and send it off in two weeks, so I'm aiming for the most efficient way to sculpt the completed Laputan robot. But I also want to learn as much as I can about the lost wax process.

I'm giving myself two options

Option 1: sculpt a large scale robot (500mm) Length by (300mm) Width. Then begin the lost wax process but finishing and sending off at the point of having a 240g hollow wax shell of the Laputan robot. Admittedly this is a lengthy process and for a beginner like myself probably not possible in two weeks.

But by doing this will the amount of practical learning I'll be giving myself be worth it? Or will I just be putting myself through unnecessary stress by taking too much on in such little time.

Afterall, my two week deadline is compulsory! if I leave it any longer I'm at risk of not receiving it back in time for submission.

However, there are steps I can take to speed the process up like finding an existing STL file of a Laputan Robot and 3D printing it large scale on the Delta Wasp 3MT or Nylon printer. Replacing the sculpting time with printing time which will be much faster.

But this will cost more money and I'm already paying £125 for the bronze casting.

Option 2: Simply sculpt the Laputan robot from the 240g of wax and send it off. Giving myself no practical experience in the lost wax process. but possibly avoiding any unforeseen complication that could jeopardise the mission completely...

Before I decide I want to run through all the necessary steps for option 1.

Option 1: The lost wax process

Steps

1. Sculpt the art work out of a wax based clay and cut it up into parts such as head, body, arms and legs.

2. For each part make a hard mould using plaster. The complexity of the body part will dictate the complexity of the mould. Some body parts may require a several part mould others may only require a two part mould.

This is best done by planting the body part into a bed of clay and brushing on a thin coat of plaster to get the details, then working up in plaster thickness making each section of the mould about 5 inches in depth.

Image: 5

3. Remove the sculpt from the mould and clean up any left over clay.

4. Reassemble the mould and pour liquid wax into it and straight away pour the liquid wax back out of the mould so you're left with a thin wax shell. Repeat this process until the wax shell is around 2 - 3mm in thickness.

Image: 6

5. De-mould each body part and piece the figure back together. This is done by gently heating a metal sculpting tool and running it over the seam lines essentially welding the wax shell together.

Image: 7

6. Cut a small square out of the main body and pour a mixture of sand and plaster inside giving the wax shell a solid core. Once the mixture has cured weld the wax square back into place. This is what reduces the amount of bronze used. Only the wax shell is replaced with bronze and the core remains a solid rock.

Image: 8

It is at this point that the hollow wax shell is complete and ready for sending off to Castel Fine Art Foundry. But now knowing the full extent of this process and comparing it to the time I have, it's without a doubt that option 2 is the one I should go for.

I have achieved an efficient amount of research into the lost wax process and understand the amount of skill and experience it would take for an individual to sculpt a large piece of artwork and cast a hollow wax shell from it in two weeks.

I am not that individual and my theoretical research into the lost wax process will have to suffice.