plaster cast



Now I am pulling a plaster cast of the figure. Through a long mess of trial and error I came up with this method last fall. The results are very strong and light weight, but it does take awhile and it is fussy work. Each side of the mold must be done separately then fitted and joined together. I am working on an easier method, but so far this is the method that is the most reliable.

<It is always fun to see something that didn’t work out.
The bottom image is of a 1/4 life size figure that I tried an experiment with that didn’t work. I slurried hydrocal plaster into the mold, let it cure for a bit, then shot the mold full of expanding foam- thinking I could bypass a lot of the painstaking process I came up with for successful plaster casting last fall. 
The experiment ended as most do, with a lot of broken junk and a mess of cleanup- but more ideas of how it could work out eventually. I’ll keep on playing around and see if I can come up with something.
If you look closely at the bottom image, you can see that the mold allowed a lot of plaster to jump through-
although the mold seams perfectly, I needed to put connection bolt
holes around the figure (or maybe I just needed to tighten them up more- I hope that is it, as itis too late to put more holes in; the holes occur where the four squares of board are- the board keeps the bolts from collapsing the foam mother mold).>

Materials: hydrocal plaster, plaster bandages (dickblick sells a big box for cheap), popsical sticks, aluminum armature wire in various gages, scissors, plaster files, mold release, 5/16 allthread in 24″ and some smaller sections (for internal support/basing), water bucket, rinse bucket, wet plaster bucket, plaster bandage bucket.



Step One: prep mold with toothbrush and water to clean it out, dry it, then a quick spray of mold release if you have it. I like to pre-cut different sizes of plasterbandage: one inch strips and 2.5 inch strips work well.

Step Two: mix hydrocal with water and dabble a thin layer over entire figure making sure to cover all undercuts and etc. Put extra in the face and hands and tap the mold to release air bubbles- nose, ears, and fingers tend to trap bubbles. Keep the mold edges clean of plaster- ie the blue outline around the white figure. Start from one end of the figure and work your way to the other end (ie from head to foot) working quickly so that you don’t put wet plaster over a thickening/curing area- this sometimes leads to a double register of the mold, as the wet plaster slips between the mold and the hard plaster.

Step Three:  Another thin layer of hydrocal.

Step Four: Wet sections of plaster bandage and fold x 3 layers, then apply along entire edge of figure.
note: Step five should be done along with step four- the plaster may become too dry, and you want this layer to adhere strongly to itself.

Step Five: wet a double layer of bandage and apply evenly through figure- make sure to press out all air pockets and keep from stretching the material out. At this point I also add Aluminum wire to narrow areas such as the neck, wrists and ankles. Steel wires will rust and discolor the casting, while Al is non-ferrous.

note: the first five steps take a few hours- I recommend taking a break here or after step six. Step Seven is a long process that takes some experimentation and patience.

Step Six: repeat steps four/five giving special attention to stress areas such as the neck, arms, legs, hands, and feet. Make sure things aren’t getting too thick or the mold won’t fit back together.

Step Seven: Popsicle sticks- plaster cast them into place as supports for the feet and legs, across and up the torso, within the neck, and through the shoulder and arms. Some may be wedded entirely to the figure, but also leave some attached only at each end so it “floats” above the plaster- there is space behind it. this gives the expanding foam something to lock around later.

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