Getting inside my head

Now that the plaster is dry I can break the mould out from the shutters.

 

I'd placed the brain form onto a bed of clay to stop ant plaster seeping underneath.  I removed this clay first and discarded it (all the clay will be cleaned and recycled) and then I carefully removed the modelled clay as I will need this later for calculating my glass requirements.

I then spent as much time as needed to make sure the mould was very clean as any particles of clay remnants will be found by the glass and be very noticeable.

In the picture above you can see the main mould and also the plaster plug that will help to create the hollow.  The pictures below show that some damage was suffered when removing the clay; the plug suffered a crack on the stem and the some plaster crumbled from the frontal lobe area.  

I created a new plug however this time I made the stem thicker so that I can carve it to shape and size.  I have also incorporated a section to create an infill for the lost frontal lobe area.  Both parts have had wired inserted for strength and also to assist with suspending the plug at the casting stage.

Now to work out how much glass I will need. To do this I will use the water displacement method. I have a sizeable lump of clay and should use a larger measuring jug however I've only a 1L jug to hand so I will split the clay into two lumps and carry out two measurements. 

I use a measuring jug and fill to the 500ml line and, one at a time, I place the clay into the jug.  This displaces the water causing its volume to increase.  I note the new levels - 800ml and 750ml.  I then deduct the original water level (500ml) from each reading (800-500=300) (750-500=250) and add the two figures (300+250) to get my overall clay volume = 550ml.  This means when I come to the stage of prepping my glass I will fill a jug with 500ml of water and add as much glass as it takes to displace the water to 1050ml (500ml water + 550ml of clay)