In linking a subordinate clause and a main clause, a relative pronoun functions similarly to a subordinating conjunction. Unlike a conjunction, however, a relative pronoun does not simply mark the subordinate (relative) clause, but also plays the role of a noun within that clause.
The main ingredient in most vodkas is some kind of grain, such as wheat, corn or rye. Potatoes are another common base ingredient for vodka, according to About.com.
Users claim it is the starch from the potatoes (vodka is made from potatoes) that stiffens the fabric. To make vodka spray starch you simply mix one part vodka to two parts water (I ued 1/3 cup vodka and 2/3 cup water).