How its done
Of course it all starts with an idea, an inspiration or a commission and I will then work from a photograph or a sketch. Once that's out of the way, the fun part begins - trying to get that idea into a workable form in either Plasticine or modelling clay. That is the hard part. It can take me weeks to get what I want out of the modelling medium and very often I scrap what I have done and start all over again. The end result has to be exactly what I want to produce and completely "tidied up". The casting resin will reproduce ANYTHING that I put on the model, fingerprints included, so if it shouldn't be there I have to make sure it isn't (I don't worry too much about the fingerprints)
Once I have the model, the next stage is to create a silicon rubber mould of that model. That isn't difficult in itself but it is an expensive material so I don't want to use more than is necessary and since I don't start with any "standard" size in mind, it can be tricky finding a box or container that I can use to make the mould. Supermarkets are a great source of these. The box can be cardboard or plastic, just as long as it is COMPLETELY watertight and holds the rubber till it sets and can then be removed without damaging the rubber mould. The liquid rubber will find its way out through the smallest of holes.
Once it has set, the mould needs to be taken out of the container and then the Plasticine model extracted. It is important to make sure that ALL the model has been removed. I use a red clay to make this easier as it shows up well against the white silicon rubber. The mould then has to "prove". You can use it immediately, but if you leave it for a few days, you can use the mould longer and get more castings from it.
OK now comes the moment of truth. Have I created a good mould, with no unwanted air bubbles? Have I extracted all the Plasticine? Only one way to find out - cast it.
First I have to decide the material I want to use for the casting. If I just use the resin, I will get a rather nice opaque, pinkish cast. Nice but not what most people want. Let's say I want to cast the sculpture in bronze resin.
This is a two part process. First I mix some finely powdered bronze (it's call Sinctered bronze) with some resin. The secret is to put as much bronze powder into the resin as you think it will hold (about 50%+ by weight). The reason is that you want to have a good bronze surface in your finished product so you can patinate it. HOWEVER, bronze powder is very expensive so you need to use as little as possible. The way around this dilemma is to just coat the mould with a thinnish layer of bronze rather than filling it completely with the bronze mixture. So at this stage I add the resin catalyst to the resin/bronze mixture (which will start it setting hard and warm) and I start applying the bronze layer. You have about 15 minutes or so for this process before the resin becomes too hard to work. Again, you have to make sure that you get the bronze mixture into every little nook and crevice and that it is thick enough on the sides. The bottom of the mould will normally have a plentiful layer through gravity but the sides can be tricky to do. When I am happy with it I let it set.
When it is set and cool, the rest of the mould can be filled with a cheaper resin mixture. I like to use a mixture of resin and slate powder if I am casting bronze or brass. I gives a nice weighty feel to the sculpture and helps to hide any small areas where the metal mixture didn't get to (each piece is unique). Then I let that set solid and leave for 12 hours at least.
Now carefully remove the final sculpture from the mould. It will be a dull brown object, which (hopefully) perfectly copies the original clay model. What I want to do now is to expose the bronze surface.
Using wire wool, I carefully rub down every element of the sculpture's surface. Because the resin is softer than the bronze, the result is that the soft resin is rubbed away leaving a pure bronze surface. Once I have reached that stage and have blown off any iron wool filings, I can "age" the piece by painting a special chemical onto the surface which reacts with the copper in the bronze or brass and turns the sculpture green wherever I paint the chemical. I repeat this until I have the desired effect. I could just sell them as cleaned bronze objects and they would weather naturally over time but this method speeds up that process. The bronze can be highly polished if required and lacquered to keep it from ageing.
And that's it. Not very difficult if you make sure each step is done properly but it does take time. From start to finish if you have created the original clay model (which can take weeks sometimes), each casting will take a full day to a week to get to the finished product. It's a bit quicker using marble or slate as there is no ageing needed and a bit longer if I use two materials such as bronze and marble in the same sculpture.
It's why the garden centres and on line auction sites are full of cheap, mass produced, "reconstituted stone" (concrete) pieces which generally have no individual flare or artistic merit.
I strongly believe people deserve better than that and that the extra cost is worth paying for a unique and individual sculpture.