Glycerine or corn syrup-based fake blood works well when the blood needs to be drippy and applied to the skin, but if you want blood spatter on clothing or objects that holds up, diluted acrylic paint is a better alternative. Acrylic paint dries permanently on fabric, and it won't fade or wipe off. You can apply it as spatter that doesn't become soaked in or you can use it for a blood-soaked look that keeps its appearance when dry.
Mix about 1/4 cup of acrylic paint with 1/4 cup of water in a container and stir continuously until it's well-blended.
Add a tiny amount of blue and green to the red paint and stir until it's completely mixed. You don't want the fake blood to be bright red, but rather a reddish-purplish brown. Adjust the pigment if necessary.
Pour about 1 tbsp at a time into the container to dilute it further to your desired consistency. If you want a splattered look, make it a little thicker than real blood; for a blood-soaked look, make it thinner.
Dip a paint brush into the fake blood and flick your wrist toward the item you want to bloody to give it a spattered look. Use a sponge to apply the fake blood for more of a soaked look.
Use a colour photo still from a horror film as a guide when mixing the blood colour. You can combine acrylic paint and a glycerine or corn syrup-based fake blood for a non-drying blood that's more viscous than diluted acrylic alone and more opaque than syrup blood.
Do not get acrylic paint in your mouth or eyes.