My wife is involved with pottery. Last week, someone came into the pottery school where she works looking for clay wine goblets that are unglazed on the inside. He claimed that the unglazed pottery removes (or in some way alters) the tannin in wine. I've never heard of this, but one of the other pottery teachers who has been at it for many years seemed quite well aware of what he was talking about. However, she is not especially knowledgable about wine, so I didn't get much of an explanation.

Has anyone else ever heard about this? If so, can you explain?
Original Post
From the info in tannic bastard's research, it sounds as though they are basically talking about fining (removing certain particulates) with clay. But this article refers to raw, un-fired clay.

As a sometime potter myself, I wouldn't drink wine (or water or anything else) from an unglazed clay container. The clay adds a distinct earthy flavor. I'd much rather taste the wine itself.

The other drawbacks would be the thick rim and the shape of the bowl, which definitely impact the perception of the wine. Bring on the crystal stemware for me.

Cheers!
Gloria
quote:
The other drawback would be the thick rim and the shape of the bowl, which definitely impact the perception of the wine

I think you'd rather think in terms of a decanter or a funnel, depending on how fast-acting the binding process might be.

Rather than dumping an overly tannic wine, it might be interesting to see if it could be made more palatable.

We need more info, or else a controlled test. Got any lab rats on the forum? If not, we'll just use houmans.
Ok, here comes the chemistry lesson.

Clays are aluminosilicates. Think of it as sandwich (double, triple, quadrupl or more decker sandwich). Bread slices are silicate layers, mayo is aluminum oxide layer. They are bonded together. (spread mayo on your bread and try to take it ALL off, virtually impossible).

Ok, now the sandwich filling (meat) are usually ions (sodium, potassium, calcium, magnesium even other metals, lots of research being done in using clays to bind (heavy) metals like lead, cadmium, etc..)
These don't come out easily (mayo keeps it sticky), but if you pull on the side, it slips out. The clay can actually (in the fining process) affect the type of ions (electrolyte) in the wine, but will not had more (must maintain electrical charge balance)

Now, clays actually swell in water (put your bread in water, never mind consistency, but it gets bigger)

Back to the sandwich. If the spacing between your slices of bread is wider, you can slip in stuff without taking the sandwich apart (slip in a pickle slice).
This is how tannins get small ions or molecules get into the clay.

Tannins are fairly large molecules, and would not fit in between the clay layer (like trying to put a whole turkey in between two slices of bread).

Back to the fact that clays swell in water, and become sticky mushy (like wet bread).
Throw dry pieces of bread on the turkey, nothing happens. Throw slices of bread that soak in water, you can probably build up a good layer of soggy bread on the turkey.
That's what fining is. The clay stick to the tannins, and has the clay is precipatating/depositing in the bottom, it drags along the tannins.

Why some tannins stay in the wine, throw wet bread on a quail, throw wet bread on the turkey. Pick but poultry up and shake lightly a bit. Probably all the bread (even wet) on the quail fell off. still some left on the turkey.
The clay just doesn't well enough on the smaller tannin molecules to pull all of them out of solution.

To make things even more confusing, different types of clays behave differently (different types of bread are more stiff like rye, vs. white bread), and are different size (small bread bun, to a whole pumpernickel loaf).


Sorry about the sandwich analogy, but I'm having lunch.


To wrap things up. Fired clay, actually binds (forms chemical bonds) between the small clay powder to form a whole solid mass, your goblet.

As for the earthyness, those are probably minerals leaching out. The goblet would not have any appreciable effect on the tannins levels except for the small amount that might be adsorbed on the surface of the fired clay. (unglazed fired clay surface to use an analogy, would be a piece of toast. Even wet, meat wouldn't stick much to the surface).


Hopes this helps. I've tried to dumb it down as much as possible. Not CHEM 101, more like CHEM 001
carried,

No one ever said I was a good student, and CHEM 001 was not one of my stronger courses. I got a little lost in the story with the turkeys and the quails, and the wet bread and all.

So let me see if I got it straight...

I can use wet clay to bond with tannins, with some success, but I might not like the sludge at the bottom of my wine glass. Or I could use fired clay and I might as well be toasting my turkey sandwich, but the tannin will stay.

The only thing we didn't discuss is the gluten content of bread which can make it stretch like an elastic or bounce like a rubber ball. Can you slip a turkey between two slabs of gluten? A topic for another day...
My wife made 2 ceramic wine glasses as prototypes for me to try out. Both are glazed nicely on the outside and about 1/2 inch down from the top on the inside. The shapes are a bit different, but both look like an oversize champagne flute. Just one is flared more (reminds me of a glass used for grappa or single malt scotch) than the other. I think a burgundy shaped bowl would be preferable.

I need to find a really tannic wine in my cellar to test its flavour in the ceramic container versus glass.
Since I last posted here, I was given two ceramic 'wine cups' made by Barbara Taylor of Earth Works Pottery. She apparently has been making these for many years, and I must admit her wine cups look much more refined than those my wife made for me. The ones from Barbara Taylor are shaped very similar to the stemless bordeaux glasses made by Riedel, and they look quite refined. The ones that my wife made for me look more like pottery than actual glassware.

Last weekend, we had some guests at our house and used the occasion to road test the ceramic wine cups made by Barbara Taylor. (We chose these to try out because I had several of them which allowed all of us to participate.) The comparison was to Schott Zweisel bordeaux glassware.

The wine used was 2003 Taja Reserva, which is blend of Mourvèdre, Cabernet Sauvignon, Tempranillo and Merlot. I discovered that this wine isn't really tannic, but I would describe it as a bit gamy and a little sour. At first I didn't find any difference, but then after about 10-15 minutes, I thought that some of the sourness, and perhaps some tartness/acidity as well, settled down and the wine tasted smoother out of the wine cup versus the glass.

Although I was not able to assess the effect on tannin, I do think that the unglazed ceramic was doing something to the taste of the wine - and the impact seemed somewhat positive. In any case, I don't agree with the rating (WS90) that the Taja was given - I'd give it something closer to 87. So perhaps ceramic cups might be a way of smoothing out those mediocre mid-80's Bordeaux wines that sometimes taste so sour.

Any conclusions seem unwarranted on just this one trial, so we'll try it again.
quote:
Originally posted by on the wine:
The wine used was 2003 Taja Reserva, which is blend of Mourvèdre, Cabernet Sauvignon, Tempranillo and Merlot. I discovered that this wine isn't really tannic, but I would describe it as a bit gamy and a little sour. At first I didn't find any difference, but then after about 10-15 minutes, I thought that some of the sourness, and perhaps some tartness/acidity as well, settled down and the wine tasted smoother out of the wine cup versus the glass.

Although I was not able to assess the effect on tannin, I do think that the unglazed ceramic was doing something to the taste of the wine - and the impact seemed somewhat positive. In any case, I don't agree with the rating (WS90) that the Taja was given - I'd give it something closer to 87. So perhaps ceramic cups might be a way of smoothing out those mediocre mid-80's Bordeaux wines that sometimes taste so sour.


That's kind of interesting. So would the 87 be coming from the Schott Zweisel or the ceramic cup?
My wife is infected with the pottery bug and we have loads of all types at home, including drinking vessels both glazed and unglazed. We tried the unglazed once and didn't like the texture or the slight flavor imparted to the wine.
quote:
Originally posted by WEc:
quote:
Originally posted by on the wine:
The wine used was 2003 Taja Reserva, which is blend of Mourvèdre, Cabernet Sauvignon, Tempranillo and Merlot. I discovered that this wine isn't really tannic, but I would describe it as a bit gamy and a little sour. At first I didn't find any difference, but then after about 10-15 minutes, I thought that some of the sourness, and perhaps some tartness/acidity as well, settled down and the wine tasted smoother out of the wine cup versus the glass.

Although I was not able to assess the effect on tannin, I do think that the unglazed ceramic was doing something to the taste of the wine - and the impact seemed somewhat positive. In any case, I don't agree with the rating (WS90) that the Taja was given - I'd give it something closer to 87. So perhaps ceramic cups might be a way of smoothing out those mediocre mid-80's Bordeaux wines that sometimes taste so sour.


That's kind of interesting. So would the 87 be coming from the Schott Zweisel or the ceramic cup?
The 87 applies to glass stems. The ceramic cups don't really change the rating much.
quote:
Originally posted by ND:
My wife is infected with the pottery bug and we have loads of all types at home, including drinking vessels both glazed and unglazed. We tried the unglazed once and didn't like the texture or the slight flavor imparted to the wine.
I was also afraid that the ceramic might somehow impart a "flavour" to the wine, but I didn't find that, at least with the wine cups made by Barbara Taylor which seemed to have a very fine smooth grain. The cups made by my wife have a slightly rougher grain, but I don't know that this should translate into an effect on flavour.

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