How would you make it look like someone is stabbed in the face with fake blood and a Retractabe knife?

Answer 1

A retractable knife may be too heavy for this special effect. As a lighter weight alternative, find a toy soft plastic or rubber knife. Use scissors to cut the tip off as much as you want to make it seem like the knife is stuck into the face. Cut a piece of thin cardboard into an irregular shape and hot glue the toy knife onto the cardboard. Paint or use markers to color the cardboard the color of blood. Use a rolled piece of adhesive surgical tape or Duct Tape, or double sided tape to attach the cardboard to the face. (You might also use make up putty for this). Use fake blood generously to help conceal the cardboard and to ooze from the wound.

To make your own fake blood, here are some methods depending on the type of blood you need (use amounts/proportions according to eye). In this case you probably want to use the fresh blood like would be coming from capillaries in skin of the face:

Fresh or spurting blood from arteries or flowing from capillaries (like when you cut your finger) is bright red because it has its hemoglobin carrying lots of oxygen in it and that makes it more red. Make it by mixing red food coloring in white (clear) corn syrup.

Old pooled blood gets thicker and darker. Make it by mixing the red food coloring in the corn syrup and then add chocolate syrup.

Older blood that is spattered or not pooled is a little thinner than pooled and thickened blood, so make that mixture as above with the chocolate syrup and then add a little water to thin it.

Fresh flowing blood from veins has less oxygen than arterial blood and it is also carrying some wastes from the body's cells that make it darker. But, it is not blue like is often incorrectly indicated, even sometimes in school. It is darker red but it is a "cooler" shade of red, and that can be made using some blue in the mix. Make it like the pooled blood with food coloring, corn syrup, chocolate syrup and then a small amount of liquid detergent (like dish washing liquid) that is a blue color just to get a glossy darker dirty red.

But, when you add the detergent, you can't use it for blood to come out of your mouth, so instead of the detergent, when you want to have the blood come from your mouth or be on your face, use honey. So what you'll have in your mouth is corn syrup, honey, food coloring and chocolate syrup.

To make alien blood that is green or blue, just substitute the green or blue food colorings for the red.