Tag Archives: bronze

Not Just Castings – how lost wax casting works and more

At the beginning of 2016 I undertook a placement with Just Castings in Hatton Garden. This was part of the two week intensive Advanced Diploma in Creative Jewellery Making (see previous blog entry about how great this was) which I had completed the previous summer.

Their premises have since moved to a spangly new home next door at 19 Cross Street, where their knowledgeable and patient team can answer all of your silly questions (as they still answer mine on a regular basis) about their services. These services go far beyond just casting to CAD design, 3D printing, plating and finishing. However, the moulding and casting process will remain forever the most fascinating to me.

I was privileged to spend two days learning the mould making and casting processes. I gained an overview of the CAD, 3D printing, finishing and plating, which can be done there behind the scenes, whilst two of my own wax pieces took their own journey into silver and brass.

I returned for two afternoons of finishing these pieces. This involved de-sprueing – the sprue is the entry point for the metal into the piece (before my placement I called this a spout) and polishing a silver ring, also finishing and rose-gold plating a brick bead for a necklace with Chris and Adrian at the studios just down the street. There was a  professional setter working away in the same studio, so I got to take a peek at this fiddly precise work too.

My illustration of the casting process, complete with spelling mistake and bunnies which were cast from pasta shapes.

I took a lovely little refresher tour with Theo recently, for a helpful reminder of the time I spent learning the ways of JC.  The process used is called lost wax casting. Lost wax casting is an ancient technique, but this centrifugal, mechanical process is the most accurate way of achieving intricate results. This modern way of casting has its roots in dentistry. To my delight I discovered gold tooth caps on the casting trees whilst on my placement – it’s nice when traditions are upheld. Items can be brought in three different ways to be transformed into a range of metals, but at some stage they need to be a wax. You could bring in a hand-carved wax piece, a model or master to have a mould made to then make waxes or a 3D design, which can be printed or milled from sheet wax.

It’s a positive to negative to positive process. The mould making stage is to create waxes from existing objects or multiples from the same original wax and allows for more types of items to be cast. These moulds are custom made to the size of the piece from a latex mixture.

Bespoke cold moulds setting in their frames

Once these are set and the piece from within is expertly cut out by hand, the moulds are ready to make waxes using the vacuum wax injector. The hot wax cools into shape in the rubber mould and the wax is removed and another can then be made in the same way shortly after.

Wax made using a cold mould

These waxes are then skillfully arranged on specific trees in accordance to their requirements, which metal, how delicate the piece is etc. Cast in place pieces (a technique where stones can be cast within a wax piece) go separately, as they need to be in a different oven set to a different temperature. The trees go into flasks, the holes of the metal flasks are taped up and the investment (a type of plaster, made up in the vacuum mixing machine) is mixed and poured into the canisters with the wax trees inside, then left to set. The next step is for the canisters to go into the de-waxing chamber for the majority of the wax to be steamed away. This leaves just a film of wax on the impression that will eventually be filled with metal, before going into the oven overnight to melt away the remaining wax and strengthen the investment plaster. There are three ovens running on 24 hour cycles, to allow for processes like casting in place and also so that all of the casting eggs are not in one hot basket.

Vasco creating wax trees

Once out of the oven, the canister full of negative impressions left by the wax goes into one of three casting machines. The largest being the vacuum centrifugal machine. This will spin the canister while a crucible will dispense the required molten metal into the voids to reach the hollows of the end of each branch of the tree.

 


Centrifugal casting machine

Back in the day I am told this was done by sling shot, so a traditional caster would be super strong from swinging their castings around their head, pretty cool stuff!

These are then cleaned with a high-pressure washer (this part reminds me of the opening credits of The Simpsons when Homer is at work) to clean off the investment plaster.

The metal tree, free from its canister and most of the plaster then goes into acid to get cleaner and get rid of any oxidisation.

Metal tree fresh from the canister

Pieces are then cut down from the trees and prepared for collection.

Wax giraffe and metal giraffe made from a pasta piece using a cold mould and lost wax casting process

This is where the process usually stops on the casting side of Just Castings, but as you will recall, they don’t do just casting! For me I take whatever silly thing I have decided to turn into metal this time and pop off to try and make it wearable (sometimes returning to get something plated), but there is still a whole separate underground grotto of finishing down the street. If decide you would like your pieces finishing, polishing, plating or stones setting these guys have got you covered there too.

Adrian finishing a ring in the workshop

So give casting a try, it’s magical, but don’t take it lightly that even if your brother ain’t that heavy you may want an estimate before you get him cast in platinum. For a really enlightening look at their processes, Just Casting have this lovely video ,and there is a handy FAQ’s section on the website too. But if in doubt just ask, they are a delight, see:

Lil Adams is the London Jewellery School Sundays Studio Manager. Lil studied Fine Art in Leeds and lived in Melbourne before travelling about and settling in London. She now works at the British Architectural Library and enjoys making jewellery with found and natural objects and is shamelessly addicted to casting (as you can see!)


Fancy giving wax carving a try? We have some classes at the London Jewellery School and online at Jewellery School Online as well as a starter kit available.

In London

We have lots of wax carving classes at the London Jewellery School for beginners and advanced learners including an evening taster class, a five-week evening class and day classes so do check out our courses and available dates on our website.

 

 

 

Online courses

We have a FREE wax carved ring making online course with tutor Sophie Arnott. You will learn to apply your designs to your wax piece, remove excess wax and create a full 3D design of your choosing. Following that, Sophie will show you how to file your wax piece into shape, remove any file marks and sand and refine the piece ready for casting. You will also learn how to create a ring to size and some recommendations on casters to use.

beginners-wax-carving-rebecca-steiner-jewellery-school-onlineIf you enjoy that course then consider our more comprehensive beginners wax carving online course which covers ring making, pendant making. The course launches on 26th March 2018 and is currently available at a pre-sale price of 50% off. CLICK HERE FOR 50% OFF – VALID UNTIL 26TH MARCH 2018 ONLY

 

 

 

Kits

At the London Jewellery School we are also selling wax carving toolkits which have everything you need to get started! The cost is £100 and includes UK postage (for postage outside the UK please email us at info@londonjewelleryschool.co.uk for a postage quote)

Click here to see what you get in the kit and to purchase

We also have a set of three wax ring blanks for sale for £12.99 plus postage, perfect if you want to get started with rings straight away!

 

All prices are correct at time of blog publication but please note that they are subject to change

 

 

 

 

More to metal than silver and gold

One of our Jewellery Design and Business Diploma students recently had a wax carved ring cast and plated in a variety of metals and when we looked at the results a number of the London Jewellery School staff agreed that the version plated in black rhodium was particularly striking.

This, of course, got us thinking. For jewellery metal, we often think about just two main metals, gold and silver, and two main colours “yellow” and “white”. So for our latest inspirations post here are some pieces in different metals.

Black rhodium

rhodium jewellery

A black rhodium finish can bring out the facets of a geometric piece such as with this black rhodium-plated Silver Jagged Knuckle Ring by Lynn Ban…

 

black rhodium jewellery

Or provide a striking contract to stones as in this pink sapphire and silver ring from Gabriel Kabirski

 

Brass

brass jewellery

Brass is often used as a base metal to plate but you could leave it to shine on its own as with this fun ring from September Room on Etsy

Bronze

Bronze jewellery

Bronze is a very ancient metal alloy – think back to your history lessons. It is much harder than copper and is great for texture and patination Much harder than copper. This cuff by Ute Decker shows off the interesting effects that can be achieved.

 

Coloured gold

rose gold jewellery

And of course gold doesn’t have to be yellow. Rose gold is becoming increasingly popular. It brings a lot of warmth to a piece and is summery metal because it looks great against a light tan. Feather cuff by Blue Fly

 

coloured gold jewellery

Or if pink is not your colour how about green gold. This is another ancient alloy, known as electrum, a naturally-occurring alloy of silver and gold. 18K green gold, such as in this ring by Brien Thomas, is about 75% gold and 25% silver.

If you are making jewellery in metals other than standard silver or gold why not let us know by sharing a link below

In the jewellery workshop: Metal clay metal types

As subscribers to our blog or newsletter you will no doubt be aware of the existence of silver clay. However, do you know about the other metal clays that are available? Metal clay tutor and artist Anna Campbell gives you the rundown of the main metal clays on the market.

Silver and gold metal clays have been obtainable since the 1990s but other metal clays are now on the scene, giving you the opportunity to give different looks to your metal clay work. Here is some information about what is available.

precious metal clay

Pieces made by Anna Campbell from PMC silver clay

Silver

Silver clay is a putty like substance made up of silver particles, a binder and some water. It can be rolled, textured and worked in a similar way to ceramic clays. Once it is dried it can be fired with a butane torch or in a kiln. The resulting piece is 999 fine silver and of hallmark quality.

The two main manufacturers of silver clay are Aida (Art Clay) and Mitsubishi (PMC). I have used both clay types and tend to buy whichever is cheaper at the time! I don’t have a particular preference.

Silver clay is available in different forms – lump clay, syringe, paste and paper.

PMC sterling silver package

Sterling silver

Sterling silver is also known as 925. This means that there are 925 particles of silver to 75 particles of copper. British metal clay artist Lisa Cain and colleagues at the Mid Cornwall School of Jewellery experimented with mixing PMC silver clay and copper clay to make sterling silver clay and did so successfully, having pieces tested at the assay office and hallmarked 925. They subsequently also successfully did this with art clay. Videos demonstrating how to make your own sterling silver clay can be found here for PMC and here for Art Clay.

However, since this experimentation, sterling silver clay has been manufactured by PMC and is available to buy.

Sterling silver is stronger that fine silver so is perfect for making rings or other pieces that need more strength. You can also roll it out a little thinner because it maintains its strength and is a little stronger in the greenware stage (when dry but before firing) although still take care when you’re filing. It carves and engraves well. However, it does have to be kiln fired, torch firing is not sufficient. And the kiln firing is in two parts, the second being in activated carbon.

For those that are selling their metal clay pieces, sterling silver clay is an attractive option as customers know what it is and are confident buying hallmarked sterling silver. However the need for a kiln can put people off.

 

copper precious metal clay

Art Clay Copper

Copper

Copper clay is available from a number of manufacturers, for a full list see here. Art Clay Copper (at the time of writing) is the most simple of the clays to fire as it can be torch or kiln fired. Copper clay is an affordable option although not everyone likes to wear copper jewellery. However, it could be a good option for making larger pieces like bracelets.

 

precious metal clay bronze

Goldie bronze clay

Bronze

I have enjoyed experimenting recently with bronze clay. I have been using Goldie Bronze. It is also very affordable and comes in many different colours. It arrives in powder form and is easy to make up into clay with ordinary tap water. This allows you to mix up the amount you need when you need it. I have been mixing Goldie Bronze hard and Goldie Bronze soft in equal parts to make my clay. Hard is great for making bangles and rings whereas soft is easier to carve and texture so a mix of both has, in my opinion, given me the best of both worlds. Firing Goldie Bronze does also have to be done in a two part schedule in the kiln in activated coconut carbon and, if you do it right, it works. In the UK you can purchase Goldie Bronze from Pajed.

Other bronze clays are available and I am looking forward to having a play with Bronz clay which I believe carves very well.

 

precious metal clay class

Silver clay and keum boo class sample

Gold

At the time of writing 3g of Art Clay gold is £259.95! Youch! It may not surprise you to know that I have not tried using it! However, there are other ways of adding gold to metal clay. I have had success with accent gold for silver which is 24 carat gold that you can paint onto fired on unfired silver clay. It is still costly, £82.95 for 1 gram, but a little does go a long way as you are only painting a layer onto the surface of the clay.

You can also use keum boo, a gold foil that is adhered to fired silver clay. You can learn how to do this on our one day intermediate metal clay class.

 Stainless steel

American metal clay artist Hadar Jacobson has her own range of metal clays featuring bronze and copper. She has created steel clay in quick fire and pearl grey. These clays also need to be kiln fired. See her website for more information (and some amazing inspiration pieces).

 Final thoughts

The original fine silver clay is still the most reliable to fire. However, it is among the more expensive of the metal clays to work with so doing some experimenting with other metal clays could prove worthwhile, particularly if you have a design for a larger piece in mind. I really wanted to make a chunky bracelet in metal clay and am currently doing so in Goldie Bronze. The cost of the same amount of clay in silver would have been prohibitive.

You do need to fire the majority of metal clays in a kiln (with the exception of art clay copper) but you may be able to find a kiln firing service in your area if you don’t have one.

The final thing to note is that you do need separate tools for working with the different metals. Contamination from one type of clay to another can result in the piece not firing correctly and all your work is wasted. My main set of tools is for silver clay (as I started working in it I have more tools for silver!). I have a box of tools, texture sheets, clay roller etc that have just been used for bronze clay. Make sure you mark your tools clearly. In practice it hasn’t meant buying too many duplicate tools and I think the opportunity to try other metals has made the added investment worthwhile.

For a more in depth run down of the different brands of clay on the market see this excellent article from Metal Clay Academy

If you’ve been inspired to try a silver clay class why not join us for a day? The following classes are in silver clay

Beginners metal clay class

Intermediate metal clay class – in this class you get the chance to add gold to your silver clay in one of the projects

Would you like to try working with paper clay? Enrol on our silver paper clay class

Like to try to make something in copper clay? Try our silver and copper clay class