In case you were talking about the bluemats, my suscpicion on them is the are a high fired ceramic (vs. The stoneware that I am working with). I have a couple and if I remember they do not change color when saturated? There are some wine bottle waters that are terracota (lower firing than stoneware I think CRS) as well. Really only a technicality but the high fire ceramic dosent change color because although it is porous it doesn't (or is less prone to) adsorbing it. Or maybe I just went on a tangental journy by myself. Pipes work I like the clear one, cheapest of the bunch at 20 bucks (sticker price) walked out paying 110, the other 2 were 40 and 60.