In addition, the costume designer needed to be able to wash the blood completely out of the costumes between performances, the set designer wanted to prevent staining the set, and (since there was a possibility of splashing the audience) we needed to be able to assure audience members that their clothes would not be ruined. This pretty much meant no red food coloring could be in the recipe either.
Furthermore, the blood would have to be visible on both light and dark surfaces and work in several different delivery devices, including air cannons, pneumatic squibs, squeeze bulbs, blood bags and a trick knife. (For a truly excellent pneumatic squib, see Crosius' phenomenal Instructible here: http://www.instructables.com/id/Pneumatic-Squib-Tutorial/)
After experimenting with several formulas I came up with this one, which met all of the needs listed above very well, and only costs about $13.00 a gallon. Compared to some commercial blood at $60.00 a gallon or more, this is quite a bargain. If you need buckets of blood for any reason, give this a try.
Step 1: Gather Your Ingredients and Tools
Four 28 oz. bottles of orange or red ultra-concentrated dish detergent (the red frequently contains bleach - do not use any detergent with bleach)
One small bottle of ultra-concentrated Dawn dish detergent (blue)
1.5 cups of creamy sugar-free peanut butter (regular will also work)
One 16 oz. bottle of washable red poster paint
Blue washable poster paint
Black washable poster paint
Sugar-free chocolate syrup
Large pot or mixing bowl
Gallon-sized jug or pitcher
Strainer or cheesecloth