Glazed Mugs Safety

[Dina]

My friend just told me that the lemon in her tea causes the glaze of her mug to peel off.

Is it safe to eat and drink from glazed ceramics? 

[Mark C.]

More info is needed.

[Dina]

To expand a bit on Mark's comment...  I would say: "It depends..."

 

For the specific piece you described - if the "glaze" is peeling off, then I would have to assume that particular piece is NOT food-safe - for the simple reason that I would not want to ingest the material that's peeling.  (I would also question whether it is actually a fired glaze that's peeling off - or some sort of paint or other coating that was applied after the piece was fired.)

 

For ceramics in general, there are several factors that can affect whether a finished piece is "food safe":  Clay body composition, glaze ingredients; how it was fired, and even the current condition of the piece, all can make it "safe" or "un-safe". 

 

One would have to know at-least the first two factors I mentioned, to even guess whether a piece is safe. Even manufacturers who label their clay and glazes as "dinnerware safe" state that "Tableware producers must test all finished ware to establish dinnerware status, due to possible variations in firing temperature and contamination."

Thank you for this explanation. I have also heard that some glazes contain lead which I understand is unsafe...

[oldlady]

dina, where do you live?  we have members from all over the world.  if you are in the USA, you would have a hard time finding lead in any glaze you want to use or make today.  if you have very old bottled glazes, check them for content if it is printed on the label.

 

it is true that lead was used in glaze for centuries and is sometimes in glazes made in other countries even today.  not everyone who ate their food all those years ago died from lead poisoning but it was a serious danger to the potters and decorators who used it in the raw state.  that is the primary reason it was regulated out of common use.

 

where are you getting your information?  it seems you need a reliable instructor or some current, accurate data.

[Tim T]

Oldlady, I'd say that (almost) nobody died from eating their food off lead glazed wares. A well formulated and properly fired lead glaze does not leach lead, which is why it is still used in many production potteries in the world for dinnerware etc without any harm. With studio potters, I think it fair to say that many (most?) don't have the skills to ensure the glaze is safe.

As you say, the main risk of lead poisoning was to the person applying the glaze, which in the days of Wedgewood etc use lead ore. Safety legislation was first created in the UK, and eventually the US caught up despite the ceramics industry saying it would be forced out of business due to the expense of not killing it's staff. Yes, many lead free glazes have been developed, but the biggest contrbution was in using lead bisilicate, which is a frit that almost eliminates the absorption of lead into the body.