ratio of water and plaster of paris for sculpture
It's been a long time since I've used any sort of scale but if I remember right it's 100 water 70 plaster. Not quite half and half.
I'll give you my quick shortcut version. Pour water until it's about half the volume you want to end up with. Then sprinkle in plaster . Keep sprinkling until it suddenly 'slows down'. When you first start out, the plaster drops fast and then gets slower and slower as you go but there will come a point when it seems to hang on the surface before slowly sifting down into the water.
That's when you stop. Wait about 3 minutes then check to see how much water is standing on top. In a small pail, about a gallon size, there should be about a half inch of water standing on top. In a 5 gallon bucket, about 3/4".
Mix at least a speed of 1500 rpm, nice fast drill, with a paint mixer, for 3 minutes. Let stand 3 minutes, pour.
I've used things like a big spoon, when it's a small amount but you really have to keep it moving in order for each particle to become absorbed.
something to keep in mind with plaster is temperature, the colder the water, the longer to set, the warmer the water the faster - when I mix plaster I get messy I just pour luke warm water into a bucket and mix in plaster slowly by hand and keep mixing in more until it reaches the consistancy of puding, then pour into the mold right away - make sure after you pour your plaster into your mold, depending on size of project, small mold you can just tap around the outside with your hand to disturb it enough to bring any air pockets to the surface, larger pieces you may want to have on a table and have a friend help you shake the table a bit and take a stick and tap around the mold to release the air bubles - tap within reason,you don't want to kill your mold
BTW, if you use a few drops of dish washing liquid in a spray bottle of water, and use it like a mold release, before you pour your plaster, it will prevent bubbles from sticking the your mold surface.
is it possible to use a plaster of paris mould to cast cement? if so,are the principles of slipcasting applicable in casting cement?
Not the same principles for sure. There's no shrinkage in cement.
You can seal the plaster mold with a product called "One Step". You can get it from smooth-on.com. I'd used 5 or 6 coats to make sure.
Can a person make a mold of reborn baby legs, arms and head? would it be cheaper to use plaster instead of dragonskin or the cheapest silicone I will appreciate your comment. I am new at this.
HI SILICONEMAKER65. i did see a girl on youtube and she had lots of plaster moulds for making silicone dolls. she said she bought them as kits. you might find her on youtube. if i find her ill post the link on the forum. i would imagine they would take up lots of room and will be heavy they looked like ceramic plaster moulds large plaster blocks.
Yes, i have seen them. I wanted to make some smaller versions of them. It is hard to find molds on ebay or amazon. They are so heavy the shipping is outrageous.