Hi, I decided to make my molds for my porcelain bjd again. In my previous molds I used dish soup to prevent the plaster from stick to the super sculpey. I saw that the dish soup made a lot of tiny bubbles in my molds and when I pour the porcelain the parts comes out really poor. I think of use Vaseline instead of the dish soup in my next molds but I not sure if it will work. Do you know if it will work? Thanks, Romi
vaseline is not the best because it can create a film inside your plaster mold that is hard to remove . This film interferes with the way the moisture is drawn away from the porcelain during casting. This results in porcelain castings that stick to the mold. Try applying the soapy release in very thin layers, waiting 4 minutes in between each layer so that the soap can be absorbed into the plaster without becoming thick and slimy. Coat the plaster with a total of 3 or 4 thin layers of soap. I use a brand called Murphey Oil Soap, it works really well, I don't know if this is available to you. If you decide to use vaseline, you should clean your plaster mold with isopropyl alcohol before casting in porcelain.
Post by EarthShine Doll on Jul 6, 2016 22:10:59 GMT -8
What I have read and discovered also through different attempts is that plaster will "curdle" if your soap release hasn't dried sufficiently. I had previously used Dawn soap, and would pour my plaster as soon as I had painted the soap on. My molds would be horrible and crumbly. oops! So try slowly painting the soap over your piece, try not to swoosh around and make too many bubbles and suds. Let it dry for a few minutes and do another layer. Let it dry more while you prepare you plaster. Getting your plaster right can be tricky. You don't want to pour it while it's still too watery or it will start to dissolve your soap and you'll get poor quality. I've had the best results waiting until it's around the thickness of a thin yogurt before I pour it into my molds. on another note- I've heard you can even use WD40 for a mold release. I've never tried it, but might be a good option, it's water soluble, unlike Vaseline.
The grey primer is used to seal the sculpture (usually made from paper clay) and to help even out the surface of the sculpture. The primer may also help the sculpture release from the mold. You would still want to use soap on the plaster parts when making a 2 part mold. Is this the product you are thinking of? www.mr-hobby.com/en/itemDetail.php?iId=241
I think this type of primer is used when people want to have a resin casting made for their doll. You don't need this primer when making a doll for a plaster mold. You can achieve high level of smoothness without primer if you are using sculpey or paper clay you can sand the surface (wear respirator) I never use a primer, it is not necessary.
Hi, I made some of my molds with thin layers of dish soup and it came out much better than the last time. I would like to ask how can I make molds for small hands with separate fingers? I want the Hands molds to save most of the details and in the previous times I made molds for hands with separate fingers the hand lost its shape and the fingers came out broken...
Hi ayamish it is difficult to make a mold with separate fingers because of undercuts and fragility. My advice is to sculpt them with a little bit of clay (or whatever you are using for your first sculpt) in between the fingers, once you make the mold and cast the hands you simply trim the extra porcelain from between the fingers with a sharp blade. Hands take a long time, even with a mold. You can sculpt quite a bit of detail, fingernails, wrinkles, lines into the hands and the detail will be picked up by the plaster mold. Also I find it helpful to spray my plaster mold with white vinegar prior to casting, this seems to prevent the castings from sticking to the mold and the release better with fewer incidents of cracking and breaking. Good luck!
Hi, I finally finished my plaster molds, They came out much better than the last time, But I have a question about the drying time of the plaster. Most of my molds are already dried (I made them few weeks ago) but I rinsed them in water today, how long it will take them to dry after that? And I wanted to know if you have any tips for working with porcelain and for sanding the parts after taking them out from the molds (in my previous molds the parts came out broken). Thanks, Romi
Post by EarthShine Doll on Aug 23, 2016 22:11:02 GMT -8
Congrats on your new molds! Oh my gosh they are so time consuming! Drying time will vary depending on your location, how wet the molds got, how thick the molds are, and what kind of air flow you have. You can definitely help the process along though. You can set them in front of a fan to help evaporate all the moisture. If they still feel cold to the touch they are still wet. I've had new molds sitting in front of a fan for a couple days and were dry...so you don't have to wait too long. Just make sure they aren't cold when you touch them.
My tip for working with porcelain is this: be patient with yourself and take time to experiment and learn. Don't rush when pouring the slip, and especially don't rush removing them from the molds.
The parts can break for a number of reasons- poured too thin, rushed the removal, a possible undercut the piece is getting stuck on...just experiment with different thicknesses and drying times to find what works best for you. Fingers always seem to break, for me anyways! It's an easy fix though, a little fresh slip and you can "glue" the parts back together.
I've tried a few different cleaning methods, and I found that adding detail, removing seams, fixing blemishes is best done in the leather hard stage. Lots of slips you can clean and smooth with a little soft brush and water. I let them get bone dry and then I sand them as smooth as I can get them while the porcelain is soft and unfired. It's like sanding chalk. You definitely should do this in a safe place and wear a mask so you don't breath the dust in.(It's super bad for your lungs.) Then I soft fire, wet sand more and more. Don't rush this part either...take the time to get in all the little nooks and crannies with whatever tool works best. (I use sponges, super fine sand paper, paint brushes, everything really, I have a tool bucket, haha!) This is just my method, every artist does it a little different, find what works best for you! sooo....then let the pieces dry, then bisque fire! easy peasy, right?
Sorry, this turned into a book, hope it helps some! Post some pics of your progress(if you want!)