Brew Cork Glass Cup Microwave Safety: What You Need to Know
By KeepCup® | Reusable Cups, Bottles & Bowls — Made for ... | Published: 2026-10-18
Category: Product Reviews
Wondering if your KeepCup Brew Cork Glass Cup is microwave safe? We break down the risks, the likely cause of damage, and when it's better to skip the microwave.
Quick Answer
The Brew Cork Glass Cup is not designed for microwave use. While the glass body alone might withstand brief heating, the cork band can dry out, crack, or loosen, and the cup may become too hot to handle safely.
Why the Cork Band Is the Main Concern
The cork band on the Brew Cork Glass Cup is a natural material. In a microwave, cork can lose moisture rapidly, leading to shrinkage, cracking, or a loose fit. Over time, this compromises the grip and the overall look of your cup.
Even if the glass doesn't break, the cork can become brittle or develop an unpleasant odor after repeated microwave exposure. KeepCup designs the cup for daily reuse with hot and cold drinks, but not for the direct, uneven heat of a microwave.
What About the Glass Body?
The glass used in the Brew Cork Glass Cup is borosilicate-like, which can handle hot liquids poured in, but it is not tempered for microwave use. Sudden temperature changes—like a cold cup going into a hot microwave—could cause thermal shock and cracking. The cork band also insulates the glass unevenly, creating hot spots.
A Safer Way to Heat Your Drink
If your coffee or tea has gone cold, the safest option is to pour it into a microwave-safe ceramic mug or heatproof glass measuring cup. Once the liquid is hot, transfer it back to your Brew Cork Glass Cup. This avoids any risk to the cup and keeps your drink at the right temperature.
Diagnosis: Is Your Brew Cork Glass Cup Microwave Safe?
- Symptom: You want to reheat a cold drink directly in your Brew Cork Glass Cup using a microwave.
- Likely Cause: The natural cork band can dry out, shrink, or crack from microwave heat. The glass body may experience thermal shock if heated unevenly.
- Corrective Action: Pour your drink into a microwave-safe ceramic or glass container to heat it. Then transfer the hot liquid back into the Brew Cork Glass Cup. This method protects both the cork and the glass.
- Stop Point: Do not place the Brew Cork Glass Cup in the microwave. If you need a reusable cup that is microwave-safe, look for a model without a cork band and with a microwave-safe label. Consider using your Brew Cork Glass Cup only for serving drinks, not for heating them.
Product Facts
- Brew Cork Glass Cup: The Brew Cork Glass Cup from KeepCup combines the clean taste of glass with the natural warmth of cork. The cork band is a natural insulator, but it is not designed to withstand the drying heat of a microwave, which can damage its texture and fit.
