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Lost Wax Casting Technique

1.     Introduction

When I started thinking about possible subjects for this project many ideas came to me about possible areas of interest. My mind went back two years ago when I started experimenting with making things using different materials and techniques. It always proves to be a real challenge to actually “make” something that you have been thinking about and to choose the right materials and techniques to give shape to the original idea. I had then sketched a few things and made some wax models. I then took the models to a lost wax casting technician. The purpose of the casting technique is to convert model pieces into metal ones. I was quite fascinated with the end product. The casting procedure that had taken place behind closed doors had transformed the original sketch to something quite different and tangible. Since then I have used it quite a few times and it seemed like a good idea to investigate it further. I have realized that is a very convenient technique and that is widely used by artists and designers for both small and large scale pieces. Despite the fact that it is a technique that it is to a great extend man operated and involves the presence of technicians, it is not expensive and has satisfactory results.

What I intend to do for my primary research is to contact  people that are related to the lost wax casting technique; that is makers, technicians, designers and artists.  From the technicians, I will request demonstrations in order for me to observe the technique stage by stage and see how things really work.  I will also prepare some questionnaires for them to answer.  I want to see and have a firsthand experience of the technique, to learn how many stages this process consists of, investigate and understand them one by one. I plan to record each stage with the use of videos and photographs. Out of these demonstrations I intend to learn about the technical knowledge that this technique requires, the tools and the machines that are used. I want to learn about the different types of metals, their characteristics, their melting temperatures and which ones are the most popular and easy to work with.  Also, I want to learn about the making of small or large scale pieces and the amount of time it takes for a piece to get ready. Moreover, it is very important to know if that process is indeed capable for mass production. Another important aspect that I would to look into is why do people choose to use it and what are its advantages or disadvantages compared to other techniques.  

2.     Primary Research Document

The aim of this research and investigation is to learn the facts around the lost wax casting technique.  The methods that I used in order to collect data for my primary research were questionnaires, interviews and observation of the technique. Both casting technicians’ and designers that use this technique were interviewed and given questionnaires.

In order to gather information about the technical procedure I contacted a number of makers and technicians. I was given the chance to visit a workshop watch them work and also participate in the process. The lost wax casting is a technique that converts models and prototypes into metal pieces. This conversion/ transformation is not an easy thing. The piece in order to be completed has to go through many different and complex stages. In the beginning, the whole process was demonstrated and each stage was thoroughly explained.  As the process was repeated, I had the chance to observe and record each stage.  

There are six stages in the process. The production of the mould, the wax stage, the investment, the wax removal- kiln firing stage, the casting stage and finally the finishing of the piece. During the first stage, a mould is created from the prototype piece. The mould is usually made out of rubber or plaster. In the second stage, the mould is filled with wax with the help of a wax injection machine (Image 1). The wax injection machine is used for its precision for a large number of jewellery casting processes. After that, in the investment stage all the wax models are attached onto ‘trees’ that group them together (Image 2).                 

Image 1                                                                 Image 2

Then the trees are placed into cups (image 3) and altogether into a machine that fills the cups and covers the wax models with ceramic mixture. The investment material that is used is ceramic cell, which is ideal for small scale designs. Ceramic shell makes the mould heat resistant. The cups are then left to cool. Then the wax removal – kiln firing stage takes place, which is commonly referred as the de waxing process. The cups are placed into the kiln. The wax softens, becomes liquid and evacuates the mould from drains that are made for that purpose, leaving a negative cavity into the ceramic shell. The metal is heated (image 4) and poured into the ceramic shell.

Image 3                                               Image 4

The ceramic shell is left to cool (image 5) and after that it is removed (image 6). Finally the metal pieces are placed into the finishing liquid that makes them shiny.

Image 5                                                                  Image 6

Each workshop can work with different types of metals. The most common ones are silver, which is also the most popular one, gold, brass and copper. During the melting process, a 5% of alloy is added to the metals. According to the type of metal, different alloy is required. Alloy is a very important element that gives balance to the metal. It is responsible for the way the final result is going to look. The melting temperature for each metal is different. Silver melts on 961°, gold on 1063°, brass on 930° and copper on 1084°.

The uses of the lost wax casting technique are several. With the right equipment, a variety of scales can be achieved. Few grams small jewellery pieces to ten tons massive sculptures can be made. Also it is a technique capable for mass production. A great number of pieces can be produced at the same time.

As far as the current issues are concerned, the casting technique has many advantages but in my opinion some very important disadvantages. One disadvantage that I immediately noticed even before the demonstration started was that it is a process with many different stages and each stage requires a lot of time, work, equipment (such as the kiln, the wax injection machine, the machine with the liquid finishing etc) and many technicians to work on. That means that a particular piece may require many hours, maybe days in order to get completed.  Also because many technicians are needed the technique becomes more expensive. For some reason this was not the case in Greece. Most of the workshops were family groups and maybe that kept the cost down. Another disadvantage is that due to the fact that a rubber mould is used as a template for the wax, each wax model has to be observed thoroughly because it is possible for some abnormalities to occur. So if someone uses this technique for mass production it has to bear in mind that a great amount of time will be lost in the examination of each model individually. The advantages of the casting technique are that it is capable for a range of scales, that is capable for mass manufacture and as far as the cost is concerned, it is considered a rather average cost technique.

In order to have a complete primary research on the casting technique, I also met and interviewed Joanna Cave, a jewellery designer, who uses this technique in her own work. The questions I asked her were why she decided to use this technique, which techniques could she use instead and why she chose not to use them. According to her, lost wax casting technique is ideal for her work because her designs are small and are reproduced in large quantities. The other techniques that she could use instead are laser cut and water jet, but compared with lost wax casting, there are much more expensive.

 Critical Analysis of Primary Research

After reading some books and visiting websites related with the lost wax casting process, I realised that although the technique follows some specific patterns, there are many variations on the materials and processes from one foundry to another.

For example in the first stage, where the mould making process takes place, some foundries don’t make moulds out of plaster or rubber but instead they scan the prototype, save it as a computer file and construct a precision mould of perfect copies. (http://www.kaparos.com/index.php/en/casting/precision-casting)

Another example of the small variations from one foundry to another is that in the workshop that I visited there was no reference to other materials alternative of wax. Wax was referred as the most suitable material but in my secondary research I found out about other less expensive ones, such as animal fat.

Whilst wax in not the only material that can be used to create suitable copies from a reproduction mould, the material’s inherent working characteristics (readily melted, mouldable, made malleable and plastic etc), and the ease by which waxes can be blended and modified to provide the user with an optimum product; means that wax products are obvious choice for producing detailed combustible patterns for casting. (Cozza, 1997 p.33)

Whilst clearly not classed as a wax product, certain animal fats closely mimic the properties of the waxes. Suitable animal fats can be used either as an alternative to wax entirely, or as an inexpensive means of ‘bulking out’ a wax based blend. (Cozza, 1997 p.33)

When the technique was demonstrated to me, during the investment stage, that I had, the ceramic shell was applied onto the wax model to make the mould heat resistant. What I wasn’t told was that ceramic cell is not the only material that can be used.

There are a variety of different refractory grids and binders available to the founder for constructing investment moulds. These refractory/ binder combinations or ‘systems’ can be variously selected for general foundry use, or for very specific casting applications. The compositions of individual refractory and binder components can vary greatly from system to system; as can application techniques, the appropriate method of kiln, wax evacuation, and the manner in which the mould is prepared for pouring. Furthermore individual founders often develop their own idiosyncratic variations of investment preparation and application method, in this respect it is not unusual to observe the same refractory material being used in quite different ways.(Cozza, 1997 p.49)

It seems that each system has its individual characteristics. Ceramic shell is perfect for small scale models but when it comes to larger ones it is not the preferable material. Plaster and grog is a traditional investment that can be used instead. Plaster and grog is less expensive and easier to prepare.

The investment material is less expensive and easier to prepare than other systems; however, moulds of this type can be prone to damage and breakdown during kiln firing and casting. (Cozza, 1997 p.58)

As far as the advantages and the disadvantages are concerned, in the interview I had with the technician, he told me that the lost wax casting is a time consuming process, but it is precise, has very satisfactory results and it is economical. He did not mention any alternative techniques. In my secondary research, I found out about an alternative process, sand casting that is cheaper from lost wax casting.

Whilst lost wax casting is a superlative process for reproducing highly detailed surfaces and intricate pattern forms, the premium material and labour cost associated with this casting technique can make its use prohibitively expensive, especially when working on a large scale. Many monumental sculptured are composed of simple forms and textures, and these designs can often equally well produced by an efficient and economically viable alternative to lost wax casting – sand piece moulding. (Cozza, 1997 p.107)

Learning about the lost wax technique and being able to participate in the procedure has been a worthwhile experience. I would like to have the chance to learn more about large scale pieces and similar techniques such as sand casting.

3.     Bibliography

Books

Brooks, N. (2005) Mould making and casting. Wiltshire: the Crowood Press.

Cozza, E. (1997) Art founding process and practice. London: Arte Nero Publishing

Website

Kaparos Foundry [Online]. [Accessed 10 April 2012]. Available from World Wide Web: http://www.kaparos.com/index.php/en/

4.     Appendix

                           Interview with lost wax casting technician

Moraitidis Grigorios, Goldsmith’s workshop, 18, Ermou Street, Athens 10563 Greece

What is the aim of the lost wax casting technique?

Lost wax casting technique converts an artist’s sculpture or model into metal.

What type of clients do you usually have?

Most of our clients are jewellery designers since this technique is perfect for small designs that need to be made in large quantities. Sculptors are also a very large group of clients for the lost wax casting technique but because our workshop is small, our equipment is better for smaller designs rather than big sculptures.

How many stages does this process have? What happens in each stage?

The process has six stages. The first stage is the production of the mould out of the prototype piece, where we usually use plaster or rubber. Then it is the wax stage, where the mould is filled with wax with the help of the wax injection machine. Then the investment stage takes place. In this stage we use a ceramic mixture that makes the mould heat resistant. The investment system that we use is ceramic shell because it is perfect for the casting of small scales. Because the jewellery designs that we have are usually small but large in number, we attach them onto ‘trees’ that group them together. Then the wax removal - kiln firing stage takes place. This stage is commonly referred to as the waxing process. There the wax softens, becomes fluid and evacuates the mould from the drains that are made. After that it is the casting stage. In this stage the melting and pouring of the metal takes place. The final stage has to do with the finishing of the pieces. The pieces are placed into a liquid that makes them shinier.

What metals do you use in your workshop and why?

The metals that we use are silver, gold, brass and copper. The reason why we only use these metals is because most of our clients are jewellery designers and look for a traditional result. A 5% alloy is added into the metals when they melt. According to the type of metal, different alloy is required. Alloy is a very important element that gives balance to the metal. It is responsible for many things such as the finish of the metal, or the pouring characteristics. The most popular metal in our workshop is silver.

What is the melting temperature for each metal?

The melting temperature for each metal is different. Silver melts on 961°, gold on 1063°, brass on 930° and copper on 1084°.

What are the current issues of this technique?

First of all this technique has lots of different stages, which means that a piece needs many hours to be completed. When we have lot of work, a piece might even need days. Secondly many technicians are required for this process, thus it becomes more expensive.

What is the possibility of scales?

With the right equipment, for example a very big kiln, the possibility of scales is massive, from a few grams to ten tons.

Is the process capable for mass production?

Yes, it is. The smaller the size of the wax model, the more pieces can be attached into the ‘trees’ that group them together, which means that we can make many metal pieces at the same time. 

                              Interview with Jewellery Designer

Joanna Cave, 64 Omirou Street, Athens, 10672, Greece

Why did you choose to use this technique?

The pieces that I design are small and are reproduced in large quantities. I therefore think that the lost wax casting technique is ideal for my work. I do the prototypes and the rest of the work is done by the technicians. The other reason why I have chosen that technique is because, compared to other methods of production, like laser cut or water jet, casting proves to be less expensive.  

5.     Images

Image 1

(Melissanthi Panagiotopoulou, Plastic mould with the wax model inside, 2/4/2012)

Image 2

(Melissanthi Panagiotopoulou, Wax models attached onto trees that group them together, 2/4/2012)

Image 3

(Melissanthi Panagiotopoulou, The cups where the wax models are placed, 2/4/2012)

Image 4

(Melissanthi Panagiotopoulou, Melting of metal, 2/4/2012)

Image 5 

(Melissanthi Panagiotopoulou, Cups left to cool, 2/4/2012)

Image 6

(Melissanthi Panagiotopoulou, The ceramic shell is removed, 2/4/2012)