Double wall glass cups are easy to spot: the coffee seems to float in the middle of the glass, with a clear gap around it. They look great in photos, but how are they to live with every day? Here is what they do well, where they fall short, and who they suit.
What "double wall" means
A double wall cup is two thin glass cups, one inside the other, sealed together at the rim with a layer of air between them. That air gap is what makes the coffee look like it floats, and it is also what changes how the cup feels in your hand.
The pros
- You see your coffee. Clear walls show the color of a pour-over, the crema-like foam of a latte, or the layers of a Vietnamese iced coffee before you stir.
- Cooler to the touch. The air gap slows heat moving to the outside, so the outer wall feels much cooler than a single-wall glass filled with hot coffee.
- Drinks stay at temperature a little longer. The same air gap helps hot coffee stay warm and iced coffee stay cold a bit longer than in a single thin glass. It is not a thermos, but it helps.
- Less sweating with iced drinks. Because the outer wall stays closer to room temperature, you get much less condensation dripping onto the table.
- Light to hold. Two thin walls usually weigh less than a thick ceramic mug.
The cons
- More fragile than a mug. Thin walls chip and crack more easily if knocked against a tap or another cup.
- A failed seal cannot be fixed. If the outer wall cracks, water can get into the gap between the walls. If you ever see water or fog between the walls, it is time to replace the cup.
- Hand wash is usually recommended. Many double wall cups, including ours, are best washed by hand.
- Avoid sudden temperature shocks. Pouring boiling water straight onto ice in the cup, or moving it from very hot to very cold, is hard on the glass.
- It holds less than it looks. The inner cup is smaller than the outside suggests, so check the capacity, not the size.
- Not for the microwave, as a rule. Unless the maker says it is microwave safe, reheat coffee another way.
Double wall glass vs other cups
| Double wall glass | Single wall glass | Ceramic mug | |
|---|---|---|---|
| See the coffee | Yes, and it looks like it floats | Yes | No |
| Outside with hot coffee | Cooler to the touch | Hot | Warm; the handle stays cool |
| Condensation with iced coffee | Very little | A lot | Some |
| Durability | Fragile | Fragile | Sturdy, can chip |
| Best for | Iced and layered drinks, pour-over you want to look at | Iced drinks on a coaster | Everyday hot coffee, big servings |
Who double wall cups suit
A good fit if you: love iced coffee, make layered drinks like Vietnamese iced coffee or a latte, like to see your pour-over, and do not mind washing by hand.
Maybe not if you: put everything in the dishwasher, reheat coffee in the microwave, want a 16 oz mug, or have a busy kitchen where cups get knocked around.
Our double wall glass cup
Our double wall glass coffee cup holds 300 ml (10 oz) and has a handle, so you can carry it from the counter to the table. A few things to know:
- It fits one phin brew plus ice, or a latte with frothed milk.
- For pour-over, 300 ml is a comfortable single mug. Our table of how much coffee per cup has the 10 oz row.
- Hand wash is recommended. Avoid sudden temperature shocks, such as pouring boiling water straight onto ice in the cup.
- You can choose one cup, a pair (Cup for Two), or a set with our handheld milk frother for Vietnamese salt coffee.
- If it arrives broken, send us a photo within 7 days of delivery and we will send a replacement or a refund.
How to make iced coffee in a double wall cup (safely)
- Brew your coffee hot into an empty server, or into a separate cup.
- Fill the double wall cup with ice.
- Pour the brewed coffee over the ice. It is no longer straight off the boil, which is gentler on the glass.
The full method and ratio are in our iced pour-over recipe.
Care tips that make them last
- Wash by hand with warm water, mild soap and a soft sponge.
- Do not knock them against the tap or stack them tightly.
- Let a hot cup cool a little before rinsing it with cold water.
- Set it on a coaster rather than straight on stone or metal counters.
More on cleaning glass, including coffee stains and cloudy spots, in how to clean a pour-over dripper and glass server.
Common questions
Do double wall glasses keep coffee hot?
A little longer than a single-wall glass, and the outside stays cooler to hold. They are not insulated like a vacuum thermos.
Why is there water between the walls of my cup?
The seal or the outer wall has cracked and let water in. It cannot be repaired, so it is time to replace the cup.
Are double wall glass cups good for iced coffee?
Yes. They sweat much less than a single glass. Pour coffee that has cooled a little over the ice, rather than boiling water straight onto ice.
The short answer
If you like to see your coffee and drink a lot of iced or layered drinks, double wall glass is a joy every day. Treat it like good glassware, wash it by hand, and it will last. Looking for a gift? See our pour-over coffee gift ideas.
Let it drip.
— Tran Vu Doan, Phin & Clay
