My solution looks like this: The basis is to assess, inter alia, the purity of the product. The Namely, depending on the purpose, have disastrous or beneficial effects on the desired results. Each percent less than 99% will thus lead to star deduction.
A price comparison, I will also draw for evaluation. If the substance is low, or there is the same product cheaper elsewhere?
Of particular importance, I find also product safety. If the powder is perfectly packaged, or you get the stuff already when opening the shipping carton trickled counter or -getropft? If the packaging is fit for the future, or it can be expected that the substance will have eaten in 5 years? Is -in particularly dangerous Stoffen- a parental attached? -Or To children's hands easily turn up the container?
I find so when the criteria mentioned defects, there are asterisks deduction.
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Tannin is fortunately conceivable harmless. Because that little bag, in which the powder is supplied was a bit dusty from the outside; therefore considers not close properly. Not only because I would have preferred a stable plastic container with a screw cap.
The powder is indicated with a purity of 95%. Now this is not the pinnacle of what is possible. One use for food purposes and excludes itself.
I think about that one summa sumarum certainly may deduct a star.
