This is my first instuctable and I appreciate your constructive criticism! :-)
Step 1: Supplies and getting started
* Resin - I like Quick Cast from Tap Plastics
* Mixing cups
* Modeling clay or carving wax - I used Roma Plastilina #3
* Carving tools and smoothing tool
* Goof Off or similar solvent based cleaner
* Duct tape
The modeling clay that I used is called Roma Plastilina #3. It is the second hardest one that they make, which is good for making a sharp well defined mold. To get started though it will probably require heating. Just cut a hunk off and break it into pieces. Then make a small foil tray to hold the pieces. Put it into a toaster oven on the lowest setting for about 15 minutes. This will make it soft enough to form it into the shape you want. I made a disk about 3 inches across and 3/4 of an inch thick. This will be your "canvas" to create on so make it smooth and flat. After you are satisfied put it into the freezer for a few minutes to harden it up.
Step 2: Transferring an Image
Start by printing an image that is the size that you want. If you are printing text or if you care about the orientation of your image you will have to "flip" the image horizontally. I did this in Photoshop but you could also use the free program called GIMP (www.gimp.org).
Now test the transferability of your ink by placing your image upside down onto another piece of paper and putting a few drops of Goof Off or similar cleaner onto the back of the image. Rub a pencil lightly over the saturated area. Lift off the top paper. If the image transferred great! If not you may have to use a ball point pen to color in the area of your image that you want transferred. Most inkjet printers work well, but mine is toner based and required this extra step.
Once you are satisfied with the ability to migrate your design do it onto your modeling clay. It doesn't have to be perfect it's just a guide for your carving.
Step 3: Carving the Clay Mold
Now smooth out the impression with a smoothing tool. It looks like a small soft eraser on a paintbrush. Try for a uniform depth and clean edges.
Step 4: Casting the Resin
Mix the resin according to the directions and pour into your mold. Don't pour it directly into the impression rather let it flow in by pouring onto a flat area.
Step 5: De-Molding
Step 6: Final Touches
Now you have your own Soap Stamp!