i might want to try to work with porcelain clay, does this work in a alginate mold?
If not what clays would work?

You can't make a clay casting in an alginate mold. You need to make a plaster mold to make clay or slip castings.

allright, i 've read some older postings of randy and i guess plaster mold is the way to go. I use to do: vaseline and then slightly overlapping bandages in 3 layers for the pregnancy shell casts,with making it creamy in between layers, is that how i make the perfect mold to capture most detail or do you have additional tips ( i work with women who are pregnant) Any extra tips how to apply the bandages? Does it matter horizontal, vertical etc...And for those of you who worked with porcelain clay? do i put a release products in the mold before pressing the clay into it? I am sure my ? are boring for your profs , sorry,i am still waiting for a good pregnancy casting course somewhere someday. i was allready so used to the alginate. Thank you for all the suggestions coming in advance. lidia

First of all don't use vaseline. Use hair conditioner instead. Apply it and allow it to dry. It'll keep the plaster from sticking and won't add smears. Being water based it will also come off the model easilly and it won't corrupt your plaster mold.

Below is some info I sent to someone a few years ago. Some of the info may be of use to you:
Slip can be bought at most places that sell clay - pottery supplies. It comes as a powder or a premixed liquid. I'd suggest getting the liquid 5 gal. pail. It probably won't cost much more than $15. Like clay it comes in different types and cones (yes, they make porcelain slip). If, by the way, you find the slip doesn't work for you you can always use the plaster mold to press a very soft-wet clay into. As the clay/ slip starts to dry it will pull away from the plaster mold on it's own in the same way that slip will. Main difference is that slip will actually make a stronger casting as the final product.
One thing to remember is that clay and slip both shrink during drying and they shrink more when bisque fired. It may not be a great deal but it will be noticeable.
The little unfired castings you see in stores are called greenware. They're made using slip.
In order to make a slip casting you need a plaster mold. The plaster sucks water out of the slip causing it to build a shell against the plaster. Once you have an adequately thick shell (usually 10-30 min.) you pour out the remaining slip and allow the shell to start drying. The shell will shrink as it dries and separate from the mold on its own. When you remove it from the mold it'll have to be dry enough to support its own weight. There's lots of variables involved and might require a fair amount of experimenting to finally be successful. Considering what you're trying to do I'd expect you'll need your slip to be fairly thick to get a rather thick shell (casting). As it comes premixed will probably be sufficient. As you make castings the slip will get thicker as the plaster mold takes water out of it. The mold and the slip together are going to be quite heavy.
If your going to make a plaster lifecasting mold of someone I would suggest trying to do it as thin as possible (not more than1/4 in. thick). Rather than using just plaster bandages I would suggest dipping the bandages or gauze material in a thin plaster mix so it will be strong as well as thin and pick up the most detail. If you get it too thick the plaster will heat up and could cause some burns to your model.
The thicker the mold the better your results will likely be. Many of the ceramic casting molds are over 2" thick. This allows them to absorb a lot of water from the slip. A thick mold will make it possible to do 2 castings in a day. Try adding additional plaster to the initial thin mold as soon as possible. Before adding the plaster spray the mold with water. This'll help the new attach to the original plaster. Mixing white glue into the water before adding the plaster powder will also help it attach to the original plaster. When the mold is finished it needs to sit until it's completely dry. This could easily take over a week. You can speed that up by setting it near a heater or out in the sunlight.
If you make a one piece (front or back half) torso mold first you only need to lay it down (sorta like a bowl)on a table. Plug the ends where the neck, arms and legs go out with a thick wall of soft clay - this may require heavy objects to be used to help back it up. Fill the entire mold with slip as high as you can without it going over the edge. Don't stop pouring once you start if possible because it'll make a line. Keep an eye on it because as the plaster absorbs the water the level of the slip will go down. You need to keep filling it to keep the level up. After about a half hour you can remove one of the clay plugs and allow the liquid to be poured out. Get enough out so it doesn't pool in the bottom. I find that a cheap bristle brush works well to get it to move. It's sort of like pudding until it gets disturbed. Then it'll liquify and run freely.
Once the excess slip has been removed you let it sit to dry and shrink away from the mold. If necessary you can put it in a plastic bag and remove it from the mold a day later. This might actually be preferable for such a large piece. Considering how big the piece will be you'll almost certainly need some support for the shell after it's taken out. Something like old towels and a box. Freshly out of the mold the casting will probably be rather flimsy so it needs to be handled carefully. This softness can be beneficial too though. It can allow the casting to be deformed enough to get it out of the mold. If you should want to try your hand at doing something surreal this would be the time to do it. Any repairs or cleaning of seams s/b done soon after the casting comes out of the mold. Slip can be added directly to the casting to fill spots. If texturing of the skin gets smeared a wet sponge tapped on the surface will usually replace it.
If pubic hair is going to be something of a concern don't use petroleum jelly. You don't want it anywhere on the inside of the mold. It'll waterproof the area and keep the slip from forming. Instead use hair conditioner. There's a thick yellow cream type you can get at beauty shops in quart containers.It's fairly thick and resembles soft margarine in color and consistency. After the mold is done just wash it out before drying the plaster. Use the petroleum jelly at the mold seams where plaster is going to meet plaster.
There will be a problem with making a casting of a torso if there is any extension of arms. As the casting shrinks it'll want to pull in towards the center. The arms won't allow this and will cause the casting to crack. Cracks arent to difficult to patch while the slip is still wet. Just dab a little slip into them with a smal brush and push them together then texture the area with a sponge. Another solution would be to have the arms elevated so they point towards the center of the piece. In this way they should release without cracking.
You'll find there's lots of different ideas about how to do the process. You just have to try things and find what works for you. One other thing: If a casting doesn't work out you s/b able to reconstitute the slip by putting it in a bucket with water and letting it set. Before you reuse it though it's necessary to run it through a screen/ filter to remove any plaster that might have gotten into it. Plaster in a creamics piece will ruin it when it gets fired.

wow that is quite a bit of information, it is a completely new technique for me and will have to practise (again) on mini casts. I was wondering, do you have a website with photos of your work? I am allways very curious.
again thank you so much lidia www.lidiabranch.com