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22 Dec 2019

Zoku Glasscore tea infuser: is this the ultimate travel mug for tea fans?

This insulated travel bottle lets you brew tea on the go; we try it out to see if it's a good buy

Zoku's Glasscore insulated flask allows you to make your favourite loose leaf herbal tea and take it on your travels, letting it infuse on the move.

It has a glass inner bottle and plastic outer, and a stainless steel infuser that you can remove before drinking.

As well as tea, you can use the Zoku Glasscore bottle to infuse hot or cold water with other flavours such as herbs or sliced fruit.

At £30, it could be a good last-minute festive gift for the tea fanatic in your life, but does it do the job well?

We tried it out to bring you our first look verdict.

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Zoku Glasscore tea infusing flask: vital stats

  • Double-walled flask - inner glass and outer BPA-free plastic
  • 450ml capacity
  • Removable steel infuser

The Zoku has a borosilicate glass inner bottle, which is resistant to staining and shouldn't taint your drinks with unwanted flavours.

It can fit around 450ml of liquid. That's a little smaller than your average water bottle, but would be a substantial mug of tea (we're talking Sports Direct mug proportions, rather than a dainty teacup).

The air pocket between the inner and outer layers helps to insulate your drink, while also preventing it from scalding your hands and guarding against bumps and scrapes.

There's also a handy carry strap, and the bottle has a smooth edge for comfortable sipping and a silicone seal to cushion the screwtop lid.

Unusually, the base also unscrews and you can completely remove the glass inner bottle for cleaning. Zoku says this also helps to stabilise and protect the inner bottle.

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Zoku tea flask trial: what we liked, and what we didn't

We thought the Zoku seemed solidly built, smart and sturdy. It had a quality feel and has clearly been thoughtfully designed.

The outer bottle warms up a little once filled with hot water and tea, but it was still comfortable to hold and drink from. It's quite fun watching your tea infuse, and you can shake it up a bit to get things going.

You'll need to fill it quite full though, as the infuser sits quite high in the bottle.

Filling and emptying the infuser can be fiddly

The tea infuser is quite narrow, and it took us a while to get the hang of taking it apart and filling it with tea. It's too small to fit a teaspoon in, and some tea leaves inevitably spilled over the worktop.

You'll need to slice any fruit, such as lemon or cucumber, quite small to fit in it too.

Once you've drunk your tea, the sodden, expanded tea leaves are even tougher to clean out. It took quite a few sharp taps to get the leaves to emerge, and we were worried about damaging the infuser.

Drink with or without the infuser in place

You can leave the infuser in place as you travel, for a longer brew time. With tea, we found this left our drink tasting bitter and over-brewed, but it worked fine for things like lemon slices.

A built-in filter means you can drink through the infuser without getting pestered by rogue tea leaves, which is handy. But we liked that you can also remove it if you don't want to leave it infusing.

It's best to do this before you head out the door though, as otherwise you'll need to dispose of the soggy tea leaves and find somewhere to stash the infuser.

It also wasn't clear you could do this from the sparse instructions included in the box, so we had to do a tentative test run to check it wouldn't leak everywhere.

Too hot to trot?

The tea flask's double wall does a good job of retaining heat.

While this is arguably a good thing, if you're used to your tea gradually cooling in a traditional mug, it's worth being aware that your tea will stay piping hot. It can be quite easy to burn your tongue, especially if you're having black, green or herbal tea without milk.

We found our tea was still scalding hot after an hour or so. It can be hard to gauge the temperature without taking a sip, so you might want to leave the lid off for a bit before drinking, or add a little cool water before you go if you want to drink it en-route.

On the bright side, if you're keen to keep your drink hot for longer, Zoku's Glasscore flask could be just the ticket on a chilly day.

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Zoku Glasscore tea flask: should you buy it?

It can be a little fiddly, but if you're a keen tea drinker, or you're looking for the perfect present for someone who is, we think this stylish flask is a good bet.

It's spillproof, feels robust and we thought it was pleasant to use and drink from. The double-wall insulation means it's quite large, but you can easily carry it by the handle if needed.

If you aren't so fussed about the infuser, check our reviews of popular reusable coffee cups and travel mugs, and reusable water bottles - including some insulated options.