For Claymation figures, the easiest way to create blood is to make downward grooves into your material and then use bright red paint or an indelible marker to animate your blood. You might be able to experiment with liquid materials, but be warned that, depending on your character’s pose, the liquid may bleed too quickly between frames to be captured correctly on film.
A wonderful way to create a Claymation “spurting” effect is to take several different lengths of wire and cover them with red clay. You can place these into the figure’s wound, and alternate the wires between each frame in order to vary the lengths of each spray. During the post-production phase of your project, add a bit of motion blur in order to create a less disjointed look, and voila! You have created a mortal injury.
If you would like to experiment with more realistic liquids, it might be fun to examine the possibilities of Karo syrup. Use several different shades of food coloring to determine what works best for the style of your particular film.
Materials such as K-Y jelly, Vaseline and hair gel can also be dyed and are more viscous than other liquids. You can use a straw to gently coax movement from your “blood”, and also use these products to replicate other jellied unmentionables.
If it becomes necessary to display interior organs, you may want to use a pasta press to create pink or reddish-brown intestines. If you do not own a pasta press (and do not want to purchase one), you can use the palms of your hands to quickly roll spare clay into long, circular rows which can then be shaped to your liking. This is an excellent way to use old clay scraps of various colors, and will save you money on supplies!
Do not underestimate the power of food. When it comes to internal organs, nothing can be quite as organically effective as using skinned grapes, pudding, mashed bananas and even fruit roll-ups! These items can be manipulated to no end in terms of color, consistency, and purpose.
A great effect can be had with the liberal use of toothpaste. Again, this is a material which can be dyed to suit your tastes. An advantage of toothpaste is that there are many different types to choose from. You can select a traditional thick, white paste or opt for a more translucent, tinted gel. The possibilities are endless.
If your character must meet an untimely demise, knowing how to get the most mileage from your effects will create a scene that sparks conversation (and controversy!) for some time to come.