The Egyptian Sphinx I moulded in a three part mould two years ago had lots of mould lines that needed trimming which took ages to do, and even though quite pleased with them at that time,i decided to attempt a one part mould and lever it out the best that I could. Hoping to create a clean casting with no need for trimming.
So I fudged around and found my old pattern.
How I reduced the size using cheap plaster it cracked after use but I only needed it once.
I decided to reduce the stone plinth it stood on by the width of my sellotape because I felt it would lessen the angle I needed to pull the casting free of my one piece mould. A mould box made of leggo bricks soon formed the needed shape and depth needed to reduce the size of that plinth. Winding sellotape around from the bottom edge of the pattern I then stood it in the box,and filled the box with Plaster of Paris up to the top where the tape formed a neat line. So no need to mess about with clay,or expensive rubber to make this what I like to call an odd side. An Engineering term used in heavy industry within the field work of Foundries. When this was hard I encased the whole Pattern in silicon rubber by hand. This was prepared with my method of adding cornflower and oil to the silicone. Which is mixed together by well oiled hands. A few minutes work and the job was done and dusted.
My new mould with the reduction made to its height of course the pattern had been removed.
Now I needed to be able to flex the mould pulling the rubber away from the castings that I plan on making.So I started slicing off rubber from around the mould this would aid getting it to flex enough to lever and drag out a complete casting,and then flex back into shape .
So another good reduction was eventually complete.
The flimsy mould had a wash and it was time to cast the first one up. I sat it in that plastic tub which was just perfect for the supporting job.
10 Pennies worth of Plaster of Paris was poured into the mould and worked in with a brush to lessen the chance of air bubbles in the casting. A few seconds work and it was left as you see it to harden off.
20 Minutes later the first casting popped out nicely as planned. A bit of slight damage, but I only need four and a half thousand year old ruins anyway.
My hobby work on my Sphinx all worked out rather well. This is a cool way of making my own props for Sci-Fi & Fantasy story`s. To help set perhaps a spell binding scene.
Having left a fully cast up mould overnight it was sort of hard work getting it out. Normally 20 minutes after filling I remove the hard casting. So I foregot, but things are learn`t by mistakes of this kind. To make sure others do no have a head snapped off, I cut folded and twisted some wire to strengthen the head.
I will of course use the damaged one head and all.
USING WET WATER
No it is not a wind up. OK?
I have used wet water for the first time on the actual mould before pouring!
Wet Water contains just a few drops of washing up soap in a large plastic washing up bowl of yes you guessed it,water,and the rubber mould was simply dipped into this. I then used a brush to make sure all the tiny places where air bubbles tend to get trapped are full wet coated. The wet water is then poured out,and the mould held upside down so the water can drip out. While still wet the mould was cast up. Breaking up the surface area with wet water helps with the flow of the Plaster of Paris pour and cuts down on trapped air while casting up.
Nice of you to pop in. Please do call again. I am in most days. BB