Making a realistic-looking fake wound takes meticulous attention to detail, some serious sculpting skills, and, of course, lots and lots of fake blood. While you can buy stick-on cuts and bruises at any costume store, making a truly gruesome fake wound that will fool your friends takes a lot more effort.

Fortunately, effects artists and YouTube users Freakmo and Powdah have created an instructional video showing exactly how to make a realistic-looking knee wound. Using sculpting clay, silicone mixtures, paint, and other ingredients, they create a truly disgusting wound from scratch. Though the final product is gruesome, the step-by-step video is a fascinating illustration of the impressive amount of artistry and planning it takes to makes a fake wound. Check out the “Infected Knee Makeup” tutorial above.

[h/t Gizmodo]

Banner Image Credit: Freakmo, YouTube