Corn Syrup and Red Food Coloring...

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Fake blood is something I care about... If it's too purple, (like in the first SAW flick) I get a little pissed. If it's bright orange, like in the original DAWN OF THE DEAD, I laugh it off. It is an art! Too much blue, it looks purple, too much yellow you get orange... It may sound like kindergarten art class, but it is serious business.

And lighting is another thing you have to consider... You can make perfect blood, but under the wrong lighting it will light-up like a neon sign. Which is what I think happened in SAW... or, coloring adjusting in post.

...The digital age of filmmaking brings a whole new bag of tricks to the table (and most of them suck... CG monsters for example) but, I will say digital blood (if done right) is a cool effect... It allows you to do some really off-the-wall spatter stuff that would be too hard to do practically... and best of all, you control the color.