The first step is about pouring corn syrup into the cleaned glass jar. You need to realise that fake blood for the costumes is entirely different from the blood used for haunted house.
Corn syrup helps the blood stick to any surface, and eventually it stays on the walls of the house. You are required to pour no more than 6 oz. into the jar.
It is the time to add only 3-4 drops of red food colour to your syrup. You can add a little more if interested in intensifying the colour. But remember, any extra quantity may make your blood look totally fake.
Make sure the red food colour is completely mixed to the syrup. For this, turn the jar end over end but only in a methodical process.
Once the food colour is totally mixed, let the mixture settle in the jar. Now gauge the colour of your fake blood. If it does not look like original, you surely need to make a few moves.
One can darken the colour by adding a couple of drops of blue food colour. The blue shade offer a little more authentic hue. Remember, you need to add one drop at a time. After adding one, analyse the colour and add the second drop only if it is required. Again, make sure the food colour is totally mixed to the liquid.
Your fake blood is ready now. If you are not satisfied with its shade, add one more drop of each red and blue food colours. One the other hand, you can add a little water, if the colour is too dark.