Removing tannin stains from mugs

One of the problems that comes with having a serious tea habit like mine is tea tends to leave tannin stains on the mugs I use. Some mugs are worse for this than others (the T2 mug with lid and infuser set I use at work is terrible for this, going deep brown inside about the length of a week; also the mugs I got from Effin Birds are pretty bad for it as well) but generally anything you use to drink tea on a regular basis is going to get tannin stains. This is particularly a problem if you tend to forget about your cup of tea and let it get cold.

Now, normally tannin stains will come off with a bit of hot water, dish-washing detergent and scrubbing, but the thing about scrubbing is over time it damages the glaze on the inside of the mug, and it makes it harder to remove the staining. Dishwashers don't do much of a job at removing the stains either. However, I have discovered one thing which works like magic to remove tannin staining, without damaging the interior glaze of the mug, or requiring a lot of effort when you're low on spoons.

It's grated bar soap, or soap flakes, if you can find them. Soap flakes are sometimes sold in the laundry aisle of supermarkets, as special care for woollen items, but it's been a long time since I last saw them (it was the "Lux" brand at the time). What I tend to use is the tail ends of bars of ordinary old bar soap, grated up on a standard cheese grater. It's best to use some kind of protection over your nose and mouth when doing the grating, since soap dust tends to make people sneeze. Put the grated soap into a lidded container (again, soap dust is a sneeze hazard, you will need the lid).

When you need to clean a mug or teacup with tannin stains, put two teaspoons of grated soap into the bottom of the mug, and fill to the top with boiling water. Stir to dissolve the soap, and then leave it to grow cold and solidify. The soap jelly tends to contract as it solidifies, so you may want to top up with some more boiling water as this happens. Once the soap jelly has solidified, tip it out, and you'll find most of the tannin comes out with the jelly, and the rest can be wiped off easily with a dishcloth and some hot water. I tend to use the jelly as a detergent for whatever dishes we have handy at the time and do a small load whenever I'm cleaning a mug (and I'll start the mugs going when I'm getting my first cups of tea for the day).

This mainly works by the application of a long soaking time (you're leaving it to sit for long enough to cool down from boiling to cold, after all), but also because bar soap has a different chemical composition to detergents. This also means grated bar soap or soap jelly is very effective for cleaning things like stainless steel (if you have a stainless steel sink, you'll notice it comes up a bit more shiny after you've done a load of dishes with soap jelly as the surfactant). I tend to use this to clean my glass teapots as well - they have stainless steel infusion baskets of a very fine wire mesh, which can get very clogged with tannin particles - in that case, put two or three teaspoons of grated soap or soap flakes into the infusion basket, fill the teapot with boiling water, leave to cool, and you'll be able to clean most of the tannin off in no time and restore the infusion basket to "just like new" condition. Same thing works for a wire-mesh tea-strainer that's become clogged, although in that case you will need to give it a bit of a scrub with an old toothbrush or something similar to remove the tannin build-up from the mesh.

I find this a very low-spoons method of cleaning things, and I enjoy the near-magical transformation of my mugs from dingy brown to shining white again.