So I finally had a chance to taste the syrups on waffles and I think I need to heat them up to help the sugar sands precipitate out. The maple syrup had a mineral flavor, sort of like those vitamins your mother used to give you as a kid. The birch syrup had a fruity flavor, however the initial overwhelming flavor was metallic. The interior of the machine was plastic and enamel so I know it wasn't from that. Although the birch syrup seems more acid than maple and can probably pick up metal ions more easily.