What on earth is this filmy substance in my tea/mugs ?

[wherehaveallthegoodfolkgone]

Hello all,
Hoping someone can shed light on this frustrating problem. I live in a house where for the past 15 years, whenever I make a cup of tea, there's always an oily looking film floating on the top. No dishwasher. Tried scrubbing and extra rinse of cups. It's so embarrassing when I've got guests. This revolting photo is of my black instant coffee! It's all on the sides of the cups too.
Thanks for any info

I get that on black tea in extremely hard water areas?

It’s from hard water, goes away with a water filter

It’s limescale residue. I live in a very hard water area and get it all the time, although it’s worse the longer you leave the drink to brew in my experience.

Thanks all. Yes I live in a hard water area but thought the Harvey's water filter "so clear" was filtering the water. Evidently not!

Baboutheocelot what water filter do you use?

Are you using a kettle? Have you descaled it recently?

Hardwater + kettle not descaled.

I know my hot water tap filter needs replacing if I start seeing that.

You need to descale your kettle and change your filter

Edit: filters don't last forever

I find it not as bad if the milk goes in first (v hard water area) but no help if you drink it black!

Thanks all, can't remember when I last changed the filter. Will do it. Wasn't using a kettle but a small gas stove stainless steel pot, which interestingly is now whitish inside.

It's only limescale.
For info never re-boil any leftover water, as limescale precipitates out of solution at 60°c.
I used to work for a water company giving advice on this every day.

A Brita filter, I could tell when the cartridge needed replacing because we would get the scum on top of the tea again.

I use a Brita filter kettle, change the filter monthly and never have scum on top of my tea and I live in a very hard water area.

It’s limescale from hard water. Throw a tsp of citric acid in next time you boil it. Once boiled, chuck the water, rinse it fully, then refill. Will be sparkling clean.

It's likely to be a build up of limescale in your kettle.
Descale your kettle and when filling the kettle with water, use filtered water to fill up the kettle. I use a Brita water jug to fill my kettle.
You're much less likely to see this film in drinks then.

its hard water scum.

stares blankly in Scottish

My brita filters last about 2.5-3 weeks before the limescale film starts appearing.
and I use the limescale special ones
water is very hard where I am mind

Limescale from the Kettle. Likely brewed for too long as well. 4 mins brewing time is perfect (for tea)

Please can you explain this more someone who's really tired?

@healthybychristmas the limescale is in a dissolved state in cold water but when you take the temperature above 60°c it solidifies.

Limescale. You don't notice it in white tea. Harmless.

I used to have a small wire thingy which I kept in the kettle to attract the limescale. I had to clean it or change it frequently but it seemed to do the trick.

😀

I had a Scottish housemate at uni who actually screamed and dropped the kettle the first time she took a proper look at the element