How to Make a Fake Scar
To make a fake scar, start by mixing equal parts gelatin and hot water in a bowl. You may also want to add a 1/4 teaspoon of glycerin to the mixture so it doesn't dry out too quickly. Next, using a popsicle stick, draw a scar onto your skin with the gelatin mixture. Once the gelatin dries, you can leave the scar as is, or you can go over it with makeup to make it look more intense and realistic. Finally, apply a makeup setting spray over your fake scar so it stays in place.
Gather your supplies. This simple scar imitation can be accomplished without much preparation and in a relatively short amount of time. The only ingredients you will need are liquid collodion and scar colored makeup, both of which can be found at most costume, drug, or department stores. Collodion is a liquid compound that is highly adhesive and frequently used in medicine or special effects makeup. Test your ingredients. Collodion is a component that can be harsh on the skin, so you should test a small area before making your main application. This way you can be sure you do not have a negative reaction. You should also test the color of the makeup as well. Try a little bit on the location you intend to use it. Your natural skin color might offset the makeup color, making it look less authentic. Clean the soon to be "scarred" area. When your body is clean, FX makeup bonds better to your skin, creating a better seal between you and the adhesive. A baby wipe, or mild soap and warm water, will prep your skin for your new scar. Wait until you skin is completely dry before applying your collodion. Imagine your scar pattern. You may need to use a mirror if you will be applying the makeup to your face, but looking at the part of your body you will be applying your scar effects to, image the scar pattern you desire. For more complicated scar patterns, you may want to use an eyebrow pencil to faintly sketch out the pattern before hand. You might consider hash-mark patterns, jagged lines, or menacing x shaped scars for your look. Apply the liquid collodion in layers. As the collodion dries, it will draw your skin together and provide the appearance of a scar. For a more pronounced effect, you can use multiple applications. You should allow each application to dry before adding another layer of collodion. Applying the liquid collodion to areas where you have tight skin could diminish the effect. Add color with makeup. Depending on your skin tone the color you use to tint your fake scar tissue will vary greatly. Your makeup can be applied over top or underneath your collodion scar. Underneath applications of makeup will require you to put on the makeup before your liquid collodion, first allowing the makeup to dry completely, if necessary. Remove your scar when finished. Before trying to remove the scar, you should take a baby wipe and remove any makeup from your prosthetic scar. You should be able to peel off the your false scar without too much trouble with your fingers. If you are having difficulty removing your scar tissue, apply a prosthetic makeup remover, like Super Solve  or Isopropyl Myristate. Ensure you have all the necessary items. The gelatin itself that you will need is a cost effective and easy to use substance, and when applied correctly, can give the appearance of scars, wounds, or burns to your skin. To make your gelatin scar, you'll need: Gelatin applicator (popsicle stick/makeup spatula) Glycerin Gelatin (or ready-made gelatin) Hot water Makeup (scar color) Mixing cup Outline your new lines. You should have a firm idea of where your new lines of your scars will run on your body. Gelatin is very friendly when it comes to removal, so you don't have to worry about pain if you apply it to an area with hair. For more artistic scar patterns, gently drawing guide lines with an eyebrow pencil can be very helpful. You might consider hash-mark patterns, jagged lines, or menacing x shaped scars for your look. Ready your canvas. Whether this is your face or your arm, a clean and dry surface is best for applying your fake scar. A baby wipe works wonders, but if you don't have that available, a mild soap and warm water will do the job just as well. Prepare your gelatin. The simplest ratio you can use for mixing up your gelatin scar solution is 1 part gelatin to 1 part hot water in your mixing cup. The problem with this sort of ratio is that the gelatin can get dried out and shrink, putting you at risk for losing your prosthetic scar. Many FX makeup artists recommend adding some glycerin to prevent your scar from drying out too fast. Add ¼ teaspoon glycerin to your 1:1 gelatin/hot water mixture. Stir your gelatin mixture thoroughly, otherwise you might have bubbles form in the mixture and spoil the effect. Be prepared to move quickly after preparing your gelatin; gelatin solidifies very quickly. Heat up water for ready-made FX gelatin. In your mixing cup, bring enough water to surround and heat your gelatin to a piping-hot temperature. Ready made gelatin usually comes in a bottle, which you have to heat to liquefy. Once it is liquid and at a safe temperature , you can apply it to your body. It's always best to test gelatin heated this way on a safe part of your body, like on your hand or forearm, before applying a large quantity of it to your body. Apply your gelatin mixture. Using your gelatin applicator, move the gelatin over the surface of your skin in the fashion that imitates the kind of scar you want to have. Due to the fact that your gelatin will not be malleable for long, you will need to apply your scar to your body fast. If you are trying to create a scar effect over a large portion of your body, or if you are trying to create an intricate scar pattern, you may need to prepare your gelatin in several batches. While your gelatin is in the final stages of setting, you can tap it gently to create a puckered effect. Stain your scar to scare. Now that your gelatin scar is fully set, add some makeup to your scar to make it look more realistic. Foundation or concealer are great for blending the edges of the false scar, but a dash of something more livid can make your scar look like a fresh wound. Seal your makeup, if necessary. If you plan on an exciting night out, or if you're the type that can't keep your hands off yourself, you might want to consider using a setting spray to keep your makeup on your gelatin. A smear caused by an accidental gesture will leave your look less than believable. Remove when finished. Gelatin applied directly to the skin can be removed easily by peeling it off. Any stubborn bits can be loosened with warm water and a mild soap. This will ensure that all makeup and gelatin have been removed. Collect the necessary items. Many professionals, including theatre companies, often use a special kind of wax, called nose wax or scar wax, to give the appearance of a cut or wound when needed. The following supplies can be found at most costume shops or online costume supply providers: Makeup (scar color) Nose wax/scar wax Spirit gum Spirit gum remover Wax applicator (Popsicle stick, palette knife, etc.) Clean your face. Any oil, dirt, or grime on your face can make your wax bond imperfectly to your face. To prevent your scar wax from peeling off or coming loose over the course of your activities, use mild soap and water to make sure the place you will be applying your wax scar is clean. Check for allergies. Be sure that you verify the ingredients used in your scar-making products to prevent an allergic reaction. If you have sensitive skin, you should test a small amount of your products somewhere on your body before applying your scar. Avoid scarring areas that move. Movement of your body causes your skin to bunch and fold, which will put stress on your scar makeup while you are in costume. Bony areas, like the nose, chin, cheekbones, and forehead, are more likely to keep still and leave your scar looking pristine. Apply your adhesive. Some scar wax may be sticky enough, and the part of your body stationary enough, that you won't need to add adhesive to keep it stuck. Even if you don't think your scar is in danger of being knocked loose, using a little spirit gum to the back of your scar will help keep it in place for a few hours, in most cases. Apply your adhesive to the area of your body the scar will cover, leaving it slightly tacky. Take a small amount of wax initially. Depending on the brand you have purchased, there may be some small differences in wax consistency, but scar wax is often thick, much like a putty. It can be sold in tubes, which can be squeezed to dispense your wax, or tubs, which you will have to scrape/scoop with your applicator. Professionals often break off a small piece of wax to work with at first, adding more as necessary. As this kind of wax can be quite sticky, you may want to cover your applicator and fingers with a little mineral oil to make the process more efficient. Vaseline will also keep the wax from sticking to your fingers. Warm the wax. At room temperature, your wax will likely be stiff and inflexible. You can make the wax more pliable and easier to shape by kneading it with your hands, warming it in the process. You should do this until the wax is soft, but not so much that the wax loses its ability to hold shape. Create the rough dimensions. Now that your warmed up wax is ready to go, form it into the general shape of the scar you wish it to become. A long, thin scar can be made by rolling your wax into the shape of a thick thread. Start by smoothing the entire scar on your body into a neutral line on top of your adhesive. You can give the scar texture and depth by building up your wax-line, or by using precision tools. Blend your scar for flourish. Even the most convincing shaped wax might not be believable if you don't blend your new disfigurement with its surrounding skin. Liquid foundation is a good option to fill in seams between your wax and face, but you should at least use some makeup to give it the appearance of your complexion. Revert to your normal self. Apply your spirit gum (or other adhesive solvent) to the area around your scar and allow it to sit for a short while. When your scar begins to feel loose, you can peel it from your face, cleaning any residue leftover with either warm water and mild soap, or a baby wipe. 
Gather your supplies. Test your ingredients. Clean the soon to be "scarred" area. Imagine your scar pattern. Apply the liquid collodion in layers. Add color with makeup. Remove your scar when finished. Ensure you have all the necessary items. Outline your new lines. Ready your canvas. Prepare your gelatin. Heat up water for ready-made FX gelatin. Apply your gelatin mixture. Stain your scar to scare. Seal your makeup, if necessary. Remove when finished. Collect the necessary items. Clean your face. Check for allergies. Avoid scarring areas that move. Apply your adhesive. Take a small amount of wax initially. Warm the wax. Create the rough dimensions. Blend your scar for flourish. Revert to your normal self. 