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.
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.
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.
If 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
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 email@example.com for a postage quote)
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