Oil Slick like film on top of my tea.

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Oct 10th 10 10:59 pm
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Re: Oil Slick like film on top of my tea.

by Kunkali » Oct 10th 10 10:59 pm

I notice it when I make homemade chai but I attribute it to oils in the spices i use

Oct 19th 10 12:18 pm
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Re: Oil Slick like film on top of my tea.

by denholma » Oct 19th 10 12:18 pm

I also have this problem - a very visible and very greasy looking film on top; it isn't uniform but kinda in circles like when you soak something very greasy in plain water with no detergent. I always assumed it was the tea - it is less in herbal tea but very visible in black tea. However, hard water makes sense - I live in Madison SD and the water here is horrible. Most people have built in water filters for their whole house and still filter their drinking water. We rent so we can't put in one of those but we have a Pure faucet filter. The water literally eats faucets so that if you don't have a filter for your whole house you have to replace all your faucets every 5-10 years. They just kinda crumble. And the water stains showers and baths a wonderful orange/brown color in a fairly short time too. So, not too surprising to me that it is the water even though we filter ours.

Nov 2nd 10 3:50 pm
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Re: Oil Slick like film on top of my tea.

by lovemytea » Nov 2nd 10 3:50 pm

There is something in the water, don't know what yet. When the water authority tested my water they said the hardness/softness of the water was fine and I don't have any of the other things that hard water causes. I only have the "oil slick" on top of my tea. We shouldn't have to filter our water or add lemon juice to our tea. I don't know about anyone else, but, I want to just brew my tea, put my sugar and milk in my cup and pour my tea over it and enjoy it. This is sooo frustrating, I now go to my mom's and get water from her every couple days to I don't have the oil on top of my tea and so I don't have to run my tea through a coffee filter on the way into my cup. I would love to know what it is in the water. Here it doesn't matter if it's black tea or green tea or the brand.

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Nov 5th 10 8:44 pm
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Re: Oil Slick like film on top of my tea.

by teaisme » Nov 5th 10 8:44 pm

lovemytea wrote:they said the hardness/softness of the water was fine
fine for other things but maybe not tea
the hardness of municiple water varies greatly from place to place and there is no standard allowable limit. Basically anything that is >180-200 mg/l will give you scale to some degree in pipes or things used to heat water. There are many places in US that have hardness greater then 800mg/l.

Usually when there is a oil slick on tea it seems due to excessive minerals. Unless you are using those paper cups you get in coffee shops, in that case I think it is the thin coating of polyethylene resin they use over the paper(the stuff that makes it non-recyclable almost everywhere).

I'm not 100% sure this is true, but one theory is that calcium will bond with the fatty acids from the tea oils, too much calcium leads to a oily precipitate forming (the oil slick). Also the hotter the water the more this seems to form (possibly due to higher extraction of fatty oils?).

Another post above throws bicarbonate ions into the equation too.
http://findarticles.com/p/articles/mi_m ... _14365029/

So....maybe you should consider...
1)a water softener
2)try a brita/pur/gravity filter (though I don't think this will be effective if your water is really hard)
3)buy bottled water

According to wiki...streams in Texas, New Mexico, Kansas, Arizona, and southern California have extremely hard water. Curious if you lived in that area.
I live in kentucky with hard water and have come across the oil slick issue too.

Jan 8th 13 5:53 pm
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Re: Oil Slick like film on top of my tea.

by erwo58 » Jan 8th 13 5:53 pm

In 1994, chemists from Imperial College did some very careful research. They sampled the scum from cups of tea made in different ways and with different types of water, and did detailed chemical analyses to find that a key component of the scum layer is calcium. The scum, or at least 15% of it, is calcium carbonate - the rest being a lot of complex organic chemicals. In other words, it is not oil.

The major finding from this ongoing research is that for the scum to form, the water needs to contain a lot of calcium ions (more prevalent in hard water areas), while the tea leaves supply the organic chemicals.

So the answer to your question is that the scum comes from the combination of the chemicals in the tea with those in the water. To reduce the scum you could use a water softener, add lemon (or any other acid)

Jan 9th 13 5:25 am
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Location: Washington DC

Re: Oil Slick like film on top of my tea.

by jcov » Jan 9th 13 5:25 am

Geesh! After reading some of the posts here I may never complain about my tap water ever again!

But jokes aside, I've live in the middle of old cities and in really small towns. Both have the same issue for different reasons... old rusty/moldy pipe lines, in the city they take forever to replace them because of how inconvenient it is for the people and in small towns usually they find out because its too late and it busts or someone complains.

My recommendation is either using a good filter AND being EXTREMELY diligent with the filter replacements as Chip mentioned at one point it is worse to have an old dirty filter than none at all. Or buy water. I know the two sound like more expenses but in the long run is worth it for the tea, but mostly your health. I might be digesting nasty stuff and find out years later.

Some people buy Coal pieces and have 'tubs' where they 'clean' the water and its more inexpensive at some extent. I'm not sure how effective this is, but I'm just throwing it out there in case you are interested.

Hope this helps and Happy steeping!


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Nov 10th 17 3:33 am
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Re: Oil Slick like film on top of my tea.

by john.b » Nov 10th 17 3:33 am

This reference on mineral content in bottled and municipal water sources was interesting (Comparison of the Mineral Content of Tap Water and Bottled Waters):


It's from 2001, so things could have changed for any particular bottle water or local municipal source over that time-frame, but it works well for detailed background.

Nov 10th 17 1:44 pm
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Location: Guangzhou

Re: Oil Slick like film on top of my tea.

by philiplee » Nov 10th 17 1:44 pm

The only time I've had an oily film on my brewed tea is by using comparatively poor quality tap water to brew the tea. This has happened in England, Guangzhou and Shanghai. Interestingly, I don't have this problem when I use my Scottish tap water (Glasgow) or bottled mineral water.

I would assume it's either something to do with the heavy chlorination and/or other minerals of the tap water in the locations I mentioned as it was noticeably strong when running the tap water. This tap water also noticeably leaves a lot of scum on taps and sinks with prolonged use. As for the tea I drink, Yiwu Gaoshan, it's the same tea wherever I go so it's not a variable.

I found some data of Scottish water online here:
http://www.scottishwater.co.uk/you-and- ... litysearch
http://www.scottishwater.co.uk/-/media/ ... .pdf?la=en

Funnily enough, searching for English water quality was too hard in comparison. I know Scots are spoiled with good water - tastes sweet and fresh straight from the tap. No need to buy bottled water when you got water that nice for 'free'. As for the chlorine, it's there but not clearly noticeable like in other locations I've lived in.