A glass bottle from soulbottles has four materials you can name without looking anything up: sand, clay, steel and the sap of a rubber tree. That is a short list for a product that sits in a kitchen for ten years, and every item on it has a history longer than plastic’s.
Here is what the maker says about each, one part at a time.
The glass
The body is quartz sand, melted and blown in what the maker calls “an old glassblowing town in Thuringia.” The 600 ml bottle stands 25.5 cm tall and weighs 525 g. That weight is the cost of glass, and it is the main reason to choose the steel version of the same bottle instead. The maker’s own advice is blunt: glass if you want it taste-neutral, transparent and made in Germany; steel if you want it breakproof and light.
The stopper
The swing-top closure is the part to read about. The glass is rarely the question; the lid is. Here the stopper is porcelain. The maker’s help center describes it as “a silicate-ceramic material made from natural raw materials” (the German original: “silicatkeramischen Werkstoff auf Basis natürlicher Rohstoffe”).
The maker’s blog walks through how it is made. A mix of clay, loam and water is pressed into shape while wet, then dried for several hours and put in a kiln to harden. After that comes the logo, printed by hand on each stopper, then a glaze, then a second firing. According to the blog, the second firing is at over 1,000 degrees, which hardens the porcelain and makes it watertight. The closing wire is stainless steel, drawn and bent in a workshop in southern Germany.
Porcelain is a good choice for a stopper, and a kiln-fired one is hard to mistake for anything else. It is the part of this bottle I would hand to a skeptic first.
The seal
A porcelain knob cannot seal against glass by itself, so something soft has to sit between them. In most bottles that is silicone. Here it is natural rubber and chalk. The maker puts it this way, in German: “Naturgummi und Naturkreide, das ist alles”. Natural rubber and natural chalk, that’s all.
The latex is tapped from rubber trees in Sri Lanka. The maker says that in making the seal in Germany it uses no petrochemical-based chemicals and no plasticizers, and that since June 2018 all of its seals are made from Fair Rubber certified rubber.
This is the difference that matters most for our list. Almost every other bottle we have examined seals with silicone, a synthetic that we count as a small named part, which is why those bottles are Bronze. This one’s seal comes off a tree. We still rate it Bronze, for the reasons below, but it is the nearest thing to the top of the scale in the category.
The ink
The pattern on the glass is a ceramic screen print. The maker says it is fired on at temperatures of up to 700 degrees and that it resists acids, alkalis and scratches. Up to 500 dishwasher cycles, it says, will not harm it. That is a claim about the maker’s own testing, and I would take it as a maker’s claim. But the mechanism is sound: ink that is glass powder melted into the surface cannot peel the way a sticker does.
The same page carries a caveat. The bottles with silver or gold print are, in the maker’s words, “not quite as sturdy.” We have not been able to find out what those prints are made of, so we only rate the classic-color editions.
What is still open
Three things stop this bottle from being better than Bronze, and we’ve asked soulbottles about all three.
One is the logo on the stopper. The blog describes a printed logo that is glazed and fired, which points to ceramic. Nobody has said so outright. A straight answer moves the bottle to Silver.
Another is the gold and silver editions, as above.
The last is the shipping box. If it is paper and nothing else, the bottle would be Gold.
There is also a practical limit. According to the maker’s FAQ, soulbottles currently ships within the EU only to Germany, Austria and France. If you live elsewhere, this bottle is a reference point more than a purchase.
The short version
If you want to know what a bottle with nothing synthetic in it looks like, this is the closest we have found: sand, clay, steel and tree sap, assembled in one country. The materials are old ones, and each was chosen for what it does, not for what it replaces. That is a better design principle than most of what is sold as sustainable. We keep the full list on the water bottles page.