Once the slip has been thoroughly sieved and mixed, it has to be left for several hours (or preferably overnight, to allow any air bubbles to rise to the surface. If there are any bubbles in the slip they can cause tiny pin holes on the surface of faces and bodies which are a nightmre to deal with.
All of my tiny porcelain dolls start out as a few thimblefuls of slip. Porcelain slip for miniature dollmaking is specially formulated and available in a range of flesh tones as well as white and other colours, which I use for different toys.
I'm currently casting a range of toy dolls, including ballerinas, vintage china dolls and other assorted microdolls. The complete casting batch will be carried out over several weeks, and will also contain toy porcelain animals, marotte heads, Punch & Judy puppets, nursery rhyme and fairy tale characters.... all the toys I create in porcelain.
Before I start, I prepare the work area, spreading newspaper to soak up any spills. Because tiny doll moulds 'set up' so quickly, it is only possible to cast a few at a time. From pouring the slip to releasing the mould takes around 10-15 minutes, depending on the air temperature, humidity, how dry the moulds are etc, so if I try to do too many at once, I run out of time to get them all open. For this reason I usually cast up to 5 at a time.
First, I always check inside each mould and remove any dust or dried porcelain slip with a soft brush. The inside of the moulds are easily damaged and any marks will transfer to the casting. The mould below is for one of our most popular toy dolls and it's possible to see the head/torso, arms and legs outlined in the plaster.
Once checked, the moulds are tightly re-banded to prevent any seepage of the liquid slip between the seams.
The pour holes are tiny, so the only way to ensure that the porcelain slip gets all the the way inside the mould without drying out halfway down, is to use a syringe. I insert the tip of the syringe inside the mould and very slowly and carefully fill each cavity
Just before I begin filling the first mould, I set a timer for the amount of time I judge will be required for the casting to set up. This varies according to several factors and is where over 25 years of experience comes into its own! When the moulds are poured they are left undisturbed until the timer goes off. During this time, water is absorbed from the slip by the porous plaster and the slip changes from liquid to solid becoming leather-hard greenware.
Now I have to move quickly. If I leave the greenware in the moulds for even a few minutes too long they will dry out too much and crumble when they're handled. The castings must be just dry enough to easily release from the mould, but not too dry that they're unworkable.
Again, many years of experience will tell me whether the mould will release and open easily. Trying to open the mould too early will result in the casting ripping apart. Perfect greenware should release smoothly with every piece intact.
Once the mould is open, I gently remove the castings, one at a time, starting with the smallest, most delicate pieces first, usually the arms. Using a scalpel blade, I trim off the excess formed by the pour holes, and make stringing holes with another of my favourite tools. As soon as the greenware leaves the damp mould, both the air and the heat of my hands accelerate the drying process so I have to work quickly, while still handling the soft, malleable pieces very carefully. If the greenware is compressed, distorted or otherwise damaged at this stage it will be ruined. Porcelain has a 'memory' and will revert to its damaged state even when attempts are made to restore the original shape.
If I have misjudged the time, or there is any delay in opening the mould, this is the point at which the tops of tiny arms will break off, or cracks appear in bodies so this part of the proceedings is always a little tense. If the phone or doorbell rings I can't abandon my task, which is why I always give an all-points warning to everyone in the house that I'm doing a casting session and can't be disturbed UNDER ANY CIRCUMSTANCES, short of a life and death situation.
Today's session involved making stringing holes in the limbs and the bodies but other dolls might require the excision of tiny eye sockets, provision for articulated heads or other modifications to the basic structure. The prepared pieces are then placed on a board to air dry thoroughly, usually over several days.
Next week.... soft firing and soft cleaning.