Ok Its getting close to Halloween, and thats my favorite holiday to decorate for. I really like skeletons and such, but im really not into obtaining real bones (at least not my own) and the fake ones can cost a good bit. So I decided to make my own. Now this instructable will show you how to make the molds so you can make your own bones over and over. Im not going to show you how to make an entire skeleton, but with these steps you should be able to make the rest of the molds on your on.
By the way, this is my first Instructable so if you find it interesting, I would truely appreciate any comments.
Step 1: Gather Materials
Ok, theres not too much needed to make a mold.
~Object to make a mold from
~Mold compound - in our case we will use liquid latex
~Plaster cloth - used to make a frame for our latex mold
~A clean, Taclon brush. - used to "paint" on the latex. Dont use a regular paint brush. Ill explain later.
~Clay - used to make a base for the mold
~Plastic food wrap
Step 2: Preparing the Object to Be Casted
Ok, for this instructable, ill be using a jaw bone. You can use any thing. Iv even casted a human skull. Im going to show you how to do a simple cast. This will capture the detail on all the sides except the very bottom. The reason I do this is because it makes it so much easier when you remove the mold. Also, for this mold I used regular potters clay. However iv also used the modeling clay that doesn't dry out and It worked just fine. Its your preference.
First thing, take your clay and make a flat base, about an inch wider than the bone. Next build clay up around the bone until there are no gaps between the bone and the clay base you made.
The picture below was taken days after I made my mold, so the clay dried up and receded. You really dont want a gap because it causes problems when you go to de-mold.
Step 3: Apply the Latex
Simple enough, follow the directions on your latex container. The stuff I bought said to apply 6 coats. I applied 11 to be safe. The first 4 coats should be thin and cover every thing. the first few coats are the ones that capture the detail. Also be patient. Let each coat dry before adding another. Make sure you cover the top of your base also, and get into all of the crevices.
Here is a good tip. Don't use a regular paintbrush with the hair like bristles. Instead use the brushes that have the plastic bristles.
Step 4: Make a Frame for Your Mold
Again, we have to be patient. I know you want to pull the mold off and start pouring, but we cant just yet. The reason is because you have just made a floppy, unsupported mold. If you try to pour in a casting material, it'll just spill right out.
So after you have applied all of your layers of latex, and they have dried throughly, your going to wrap your mold in clear food warp. The frame itself will be made of plaster cloth, the clear wrap just makes the frame removal easy and clean.
Now you dont the warp or plaster cloth to be tight on the latex. The clear wrap should loosely hug the jaw, but the plaster cloth should kind of blanket the bone. In other words, the Cloth is going to harden, and if it curves around the bone, your not going to be able to get it off. It needs to be able to be pulled up without catching on any thing.
(ugg hard to explain but once you do it you'll under stand)
Step 5: Making Sure Every Thing Worked
Ok, now its time to see if your mold turned out ok. Gently pull off the cloth frame. If the bone kind of hangs in there (which mine did) gently pull the frame outwards until the bone releases. Note that some of the clear wrap may have became stuck in plaster cloth and is causing it to hang up. Just take your time and you'll get it out. If the frame becomes weak from working it, you can apply new layers of plaster cloth to the exterior of the frame.
Once you get the frame off, peel off the clear wrap. Then gently pull off the latex mold. Dont worry about stretching it out. Latex can be stretched pretty far if you put on enough coats.
Step 6: Actually Making a Cast
Now that you have your mold and mold frame made its time to start casting. First re-insert the mold into the mold frame. Make sure that the mold is open so that the casting material can fill in all of the areas. The latex tends to stick to itself a little, but can easily be pulled apart.
Now pour in your casting material. For this instructable I will be using plaster. One its cheap, two its easy to mix. Also plaster drys enough to be removed from the mold in about an hour. The downside with plaster is that it chips easy and does not hold up to moisture at all. After I make something I spray it with a weather resistant paint to prevent it from melting if it gets wet.
After the plaster has set up for an hour, peel off the mold just as you did off of the original. Below is the final product.
Step 7: Oh Yeah!
Sep 2, 2008. 10:50 AMDramatic Imagerysays:
If you dust the latex mold with talcum powder or regular baby powder, it will prevent the latex mold from sticking to itself.
I totally forgot something until "Dramatic Imagery" reminded me. Before you start coating your base model with the latex, you can coat it in a release agent that will help with keeping the mold from sticking to everything. You can buy some commercial stuff or do as he says and coat it with talcum or baby powder. Also, after you make you mold, coat the inside so when you make your cast they wont stick.