Newmodeller's advice would be the best for ease, speed and safety.

Please let me interject here that those bandage strips of plaster are much safer than regular plaster, because of the thinness of the cast.  Regular plaster has to be applied much more thickly (and more slowly), and thick applications WILL BURN the skin.  People have been known to attempt to make a hand or foot cast by immersing the hand/foot in a container of plaster.  By the time the plaster was heating up and they realized their mistake, the hand/foot was actually being COOKED by the plaster, and by the time they got the plaster off (usually at a hospital), the hand/foot was severely damaged and much of the skin (the whole thing, not just the top surface) came off with the plaster.  I saw a stomach-turning photo once.

I would certainly use petroleum jelly for a face, but I would use thin plastic on the rest of the body.  Hair and plaster do not mix!  Thin dry cleaning bags are ideal, as are those very thin, cheap plastic painting tarps.  Tape to form to the body.

About Newmodeller's suggestion to do only half of a limb at a time:  you don't have to do that (it's much more difficult than it sounds).  Invest in a small (5"/120mm) pair of Lister nurse's bandage scissors with the protective tip on the bottom blade (bottom scissors in this photo: www.indigo.com/.../gphtools/bandage-scissors.jpg) from a place that sells medical supplies.  They're not overly expensive, and much cheaper than a visit to a doctor for suturing a gash).

I would cover that part of the limb, such as the forearm, with only three layers of the bandage, let it set just until firm, then cut it near where the edges of your armor would be.  (For a real life mold, you would only make one cut as soon as the plaster was stiff enough to hold its shape, flex open enough to remove the body, and then put back together more more strips of bandage.)  Try to make your cuts as even and as smooth as possible.  Then cover your pieces with more layers of bandage and fold more strips along the raw edges to add strength.  Five or six layers should be enough.  Be careful to watch for warping as it sets.

I would not use a claustrophobic person as a model for a torso mold.  We won't go into just how I know this.     

VERY IMPORTANT NOTE:  When making a torso mold, if your model suddenly begins to panic about being encased, CUT THE MOLD OFF IMMEDIATELY!  Just because it doesn't make sense to you doesn't mean ANYTHING.  GET IT OFF!!!

Tape the plastic over the torso, going higher up the neck than the bandage will be, and well into the armpits and off the shoulders.  Tie up or cover all hair very well.  Build up your initial three layers, let set, then cut the form where appropriate to remove from the model.  For body armor, I am assuming you would want to do this under the arms.  Set on a firm surface like a table or board, and add more layers until if feels strong enough.  Larger pieces may require more layers.

To make a smooth form, you will want to cut the bandage into pieces, usually not longer than 12"/30cm for large areas (torso) or half that for limbs.  Try to avoid folds or pleats.  The moist bandage will stretch a bit, so take advantage of this as needed.

This plaster sets up quite quickly, so have a container of tepid water right beside you and your model.  Dip the piece of bandage into the water for a couple of seconds, then lift and let the excess water drip off, and apply.

When beginning to use the plaster bandage, notice that one side is mostly plaster (usually inside the roll) and the other is mostly gauze.  Apply with the plaster side up, and smooth firmly.  You want to work the softened plaster well into the gauze and all preceding layers, or your mold won't be strong.  If layers of your dry mold start coming apart, you will recognize that you failed to do this.  :shock:

Strengthen all raw edges (trim first with scissors if needed) by applying a strip of bandage all along the edges at the armpits, lower edge, neck, etc. 

Assuming that you will be using only PM as the casting material, you will need to waterproof the mold with acrylic paint, inside and out, before you use it.  One or two good coats should be sufficient, and don't miss any edges.

TIPS: 

Cold water slows down the setting time of plaster.  Hot water speeds it up.  Tepid water is probably best for most uses.

Don't pour excess plaster, plaster water (from bandages), plaster dust or chips down your drains.  PLASTER WILL HARDEN UNDER WATER!  Use a plastic dishpan or bucket, and let any debris harden at the bottom overnight, then dump the water part of it onto the ground (relatively alkaline, so don't put near your acid-loving plants), and scrape up the debris at the bottom and put in the trash.

Plaster must cure before sealing or use.  Curing is a chemical action, not a drying action.  You can't speed things up by putting it in the oven.  Even after it's cured, moisture will gradually be working through and leaving the plaster.  This isn't too much of an issue with thin molds like this, but can take several weeks with thick molds made from liquid plaster.  When the plaster feels 'warm' as in room temperature, it is ready to waterproof.  If it feels cool and clammy, it still needs to sit.  Placing it in front of a fan may help.

Once plaster hardens, you can't reuse it.  Don't try to use leftover chunks, chips or dust in a fresh batch.  It won't work, and will severely weaken the new batch.

For body armor, I would use the outside of the mold.  The slight difference in size due to the thickness of the plaster might be useful for padding the inside of the armor so it will be more comfortable for the wearer.  Be careful to try your armor pieces before you need to wear it for a long time:  look for high spots or rough edges that will rub against your skin.  Gluing any soft material inside the armor where it touches skin will make it much more comfortable (just like masks).

Be sure to paint the inside of your armor to protect it against moisture, and do it very thoroughly, as body moisture and oils are well known to destroy masks, etc.

I hope you post some photos when you're finished!

Sue

You're in Las Vegas?  Nevada?  There are tons of medical supply places there.  Just look in the Yellow Pages under Medical Equipment & Supplies and call around.  There used to be a place on Industrial, between Charleston and Sahara, right near the Bell Trans Limo yard.

The last time I bought a box of plaster bandages, I got them through my vet, and paid $54 for a dozen rolls. 

Sue

Sue is absolutely right, please be very careful, plaster is a chemical reaction (somewhat similar to cement in that it doesn't need air to dry and harden)  as such it is exothermic.  Even modrock feels odd as it drys.  If you have a craft store nearby try and get some from there.

Could you scavenge / borrrow a shop dummy from a local store?  It would be much safer to cast plaster over this than yourself/a friend.

With a dummy you could also experiment with sand casting using plaster.
Best of luck,
Charlotte

I couple of years ago, I read something where someone (don't you just love the details?) made a mask form from several layers of heavy-duty aluminum foil.  You would need something to support it fairly accurately, but what?

All I can think of is pantyhose filled with sawdust... 

Sue

I do have a dress form actually and it isn't nearly accurate enough.  It's also an inch too big in the bust, and with the armour I'm making, and unconformity in the size would be disasterous.  I'm thinking of either diluting the plaster and setting it into bandages or just keeping it so thin I can tear it off without hurting myself should something go wrong (it would also keep the heat down and allow for a quicker dry time).  And I'll be doing alot of spot tests to make sure the plaster won't cause problems.  If it does I'm going to cast the molds out of paper mache and make the positives out of plaster.

That's pretty much exactly what I was going to do.  Except the Paper Mache would be applied to the inside for accurate size. 8)