Storm clouds in my cup

I've no idea really but I guess it's what it's made of perhaps. What a pity because I doubt if it was cheap.

Is it still shiny? I have a similar problem with a very pretty NT cup which belonged to my late Mum. Examining it recently I noticed that it has very much lost its glaze - especially in the bottom. It is therefore quite porous and I would assume that this is why it absorbs liquids and stains so easily.

I bought DH a couple of quirky mugs from John Lewis; they are bone china and weren't cheap by any means (£12.50 each) but both stain, not as bad as yours though! Very annoying.
A drop of bleach in a mugful of water does clean them .

Perhaps your mug missed the the glazing process?

This is a question I've often pondered, yet never got an answer.

My other half's mugs don't seem happy unless coated with stains. We bleach. Then almost as we're watching, light staining appears again.

I have a fab Le Creuset mug which is highly robust and never allows the tea to stain.

Mine is heavy duty, hubby's is bone china. Maybe the latter stains easier than my builder's mug due to its delicateness.

I have loads of mugs of different sorts including bone China and Le Creuset and never get this - but I do have a water filter... is this why?

Try a Steradent tablet. It works but I don't know how long the mug will stay stain free.

I wonder if bleach damages the glaze? Then the more you bleach the worse it gets

Here's what happens.

Stains occur due to seepage of moisture through very small (and sometimes invisible to the naked eye) cracks in the glaze often referred to as crazing, crackle or pin holes.

Moisture combined with organic matter: tea, coffee, oil, fat, food and dust evolves into a bacteria that typically is brown or black in colour present between the glazed craze lines or in the clay body under the glaze. Scrubbing the surface is a cosmetic fix only.

Bacteria stains are more likely to occur on earthenware or stoneware type pottery due to the ceramic higher porosity level allowing the moisture to penetrate deeper and stay wet creating a perfect environment for bacteria to flourish. High fire ceramic such as porcelain, which has almost no porosity is less likely to stain but still will.

Crazing and crackles are a network of lines or cracks in the fired glazed surface. They usually occur at the end of the kiln firing process when the outside surface cools before the clay body under the glaze cools. Crazing can also happen during the vessel's life time due to rapid temperature changes: day and night, hot and cold water.


Do not use bleach or chlorine. Bleach or chlorine may remove the surface stains but also can damage the ceramic item more. You can use OXY cleaners for mild staining but anything that black, I’d bin too as the bacteria is too deep in the crazing and will continue to multiply.

Early, you’re a star! I just knew one of us out there would have an answer. Thank you so much.
I have suggested to the NT that before their buyers make an order they do a trial run on the expensive mugs and cups in their own homes.
My memento purchase has been very disappointing and tedious.
Thank you for all the information you’ve shared.

I think with the convenience of tea bags most of us use mugs more often than the teapot, mine tends to come out when we have guests but I remember (when young!) being told not to scour the inside of the teapot as the staining improved the flavour of the tea. Another old wives tale hits the dust

You are welcome Nonogran.

Bear in mind is that a lot of “quality” mugs are bone china. I’m thinking of the beautiful ones you can buy from Dunoon, for example. NT’s may be the same.

Bone china is usually thinner and the glaze is smoother than porcelain china but the glaze is not as durable as porcelain china since it is softer and more porous.

Yes this has happened with me with bone China mugs I bought in Waitrose. I have 6 different pattern ones all made in UK and not China. 2 have terrible staining that will not come off even with bleach or lemon juice. I’ll have a go with oxyclean as Early suggests. At the moment I hardly use them as the brown staining is very off putting.

Early

Here's what happens.

Stains occur due to seepage of moisture through very small (and sometimes invisible to the naked eye) cracks in the glaze often referred to as crazing, crackle or pin holes.

Moisture combined with organic matter: tea, coffee, oil, fat, food and dust evolves into a bacteria that typically is brown or black in colour present between the glazed craze lines or in the clay body under the glaze. Scrubbing the surface is a cosmetic fix only.

Bacteria stains are more likely to occur on earthenware or stoneware type pottery due to the ceramic higher porosity level allowing the moisture to penetrate deeper and stay wet creating a perfect environment for bacteria to flourish. High fire ceramic such as porcelain, which has almost no porosity is less likely to stain but still will.

Crazing and crackles are a network of lines or cracks in the fired glazed surface. They usually occur at the end of the kiln firing process when the outside surface cools before the clay body under the glaze cools. Crazing can also happen during the vessel's life time due to rapid temperature changes: day and night, hot and cold water.


Do not use bleach or chlorine. Bleach or chlorine may remove the surface stains but also can damage the ceramic item more. You can use OXY cleaners for mild staining but anything that black, I’d bin too as the bacteria is too deep in the crazing and will continue to multiply.

Wow…??????????????

Thanks Early. ???That will stop DH saying it’s my fault for not finishing my drinks. I’ve binned a lot of mugs in despair because of staining.
Currently I have 15 mugs. 6 from Home Bargains, 6 from a French Supermarket, a sloth mug from Dunelm for GD and two of those that change colour when you add hot liquid.
The only one that’s stained is one of those from HB and that’s only round the bottom. I won’t use bleach on it any more though.

I've never used bleach. Wouldn't. A simple, wet the vessel and then gently massage with a touch of table salt. Has always worked well for me. Takes all of two minutes

Its all in the glaze!

My Herdy and DisneyWorld mugs stain rotten - I use either steradent or sterilising liquid to clean them now and then. My Modern Toss one and my cheapy Little Miss ones don’t!

Early where did you learn that? Are you a potter?

My DH drinks black tea, and his expensive mug always has tea stains after use. I just use a scourer.

I say to him ‘Whatever do your insides look like?’

I buy the sterilising tablets used for babies bottles, much kinder than bleach, hot water goes into each mug ( we only have 2 that stain) then half a tablet and within minutes they are clean.
Mine usually stain if I forget to put them into the Dishwasher and hand wash them instead.

Kim19 yeesssss! I ‘ve just tried your salt tip and it’s done the trick. Thank you.

Namsnanny

Early where did you learn that? Are you a potter?

No Namsnanny. An interest in ceramics both antique and modern and the scientific processes involved in it. The Great British Pottery Throwdown is a favourite, especially Raku firing week and what happens to the glazes in that process.