It thins out the color so you can airbrush it onto your cake. It also works good if you need to color a small area on your cake that you cant airbrush. Just add a little color to a small amount of vodka and brush it on. The alcohol evaporates and you cant taste or smell it on the cake.
I used it on some roses I made that I still couldn't get to look any good. Thats when this came to mind,
Sorry this may be uncalled for but, I couldn't resist.....
If all fails, and you can't get it to look right,
Drink it.. 
Just had to say it. I don't mean to offend anyone!!!
People like to use vodka or everclear (which is a grain alcohol) becuase of the high alcohol content. That means that the area coated with the luster dust or color/vodka mixture will dry very quickly because the alcohol evaporates quickly. There should be no fear of getting "drunk" from having used a vodka/dust/color mixture on a cake. BUT, if using vodka is an issue, you can always usea clear extract--vanilla or lemon extract. Just don't use water.
If you just need color for an airbrush, you can just use airbrush colors. But, If you want to airbrush a luster dust, it needs to mixed into a very liquidy mixture with an alcohol based product.
I have noticed that when I airbrush it runs some. Would mixing vodka with my help with this problem. Thanks
No. If your airbrush color is running, it is because you are applying it too heavy in those areas or you are holding the gun too close to the cake.
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