I have a little confession to make: I love stage blood.
I feel guilty saying that, as if enjoying blood and gore is something only serial killers should do. I didn't have a traumatic childhood. I like puppies and kittens, the color purple, and unicorns. But I am the first one to volunteer when someone needs a gaping wound or to bleed to death on stage. I've never had a formal class; instead I have just picked up techniques over time.
As luck would have it, An Appeal to the Woman of the House required both a scar and blood!
To make the scar, I used a product called 3rd Degree. It is a 2 part silicone product sold by Alcone. I love it because it's easy to use, doesn't require a mold, and blends with the skin easily.
You'll also need wax paper, vinyl gloves (NOT latex), plastic utensils, makeup for color, and makeup brushes.
Mark two different utensils to use as scoops for each part - DON'T use the same one for both jars! Mix with a third utensil. Combining them activates the silicone and it begins to cure. You can also add makeup to match skin tone at this point. I used pressed powder.
Next create the shapes. Use wax paper, draw a shape with sharpie, and flip over (sharpie runs). For dimention, I made two parts, the top was a "skin" layer with a cut in it, and the bottom I used a little red and purple cream makeup from a bruise wheel to give that raw look under the skin. I made mine quite thin, especially at the edges. Cover with another piece of wax paper to smooth the surface. Allow to cure for about 10 minutes
Once cured, mix a tiny bit more silicone to use as an adhesive for the two layers. Peel up the skin layer, trim the cut a bit more until it shows enough of the raw layer. Spread a thin amout of wet silicone on the red raw layer and place the cut skin on top. Wait 10 minutes again. Peal up and trim the straggling ends.
When all is done you should have a pretty good (well, gross good) looking scar! I used Pros-aide as an adhesive to the skin. The scars are reusable, but make a few extra just in case. Add some blood - I used the Ben Nye Thick Blood for this one because it was a wound that was sitting for a while.
If you are a member of USITT, I have a complete power point presentation on how to make a more complex bleeding wound in their Costume Comission Poster Session Archive.