In order to replicate this experiment, I would need to know additional information such as the four different samples that they used (because I could have choosen metal, carbboard and many other sample materials that they didn't use and would get different results. Also I would also need to know the amount of vinegar to pour because this can caute a major change. Lastly, they might want to tell where to sit the samples while they dry for 30 minutes because if they are sitting in room temp. or by a light source makes a difference too.
