In competition, it's not uncommon to see Plaster of Paris in its commercial form. You should be familiar with how that behaves, too, because event supervisors may give you Plaster of Paris instead of "uncooked" gypsum powder.T-B wrote:The powder to use is Gypsum, not Plaster of Paris. Yes, chemically the same, but one has been cooked and the other not. That my account for why your results are not the same as you've seen posted.When dealing with certain powders, I seemed to have trouble determining whether the Plaster of Paris bubbles. Specific resources tell me otherwise; it could be our version, however I am uncertain. Does the Plaster of Paris bubble/sizzle?
Another thing my partner and I noticed in this event last year is that there are certain peripheral properties not of the powders themselves, but of their most easily accessible forms, that can- in a pinch- be used to identify them. For example, vitamin C powder samples were often crushed vitamin C tablets, which might have a slight pink, orange, yellow, or green tint and a citrus scent, simply because that's how the tablets were marketed. The supervisors figured it was close enough to white that it didn't matter. Similarly, Plaster of Paris samples sometimes contained traces of the fibers that it normally has in it for structural purposes. These things aren't really the most important things to know- not least because they're not always present- but it can be a good idea to be aware that if you see fibers, it's probably Plaster of Paris, and if you see a pink/orange/yellow/green tint or smell something citrusy, it's probably vitamin C. There are probably other examples, too, but those are the ones I can think of at the moment.