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LocknLock Story

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LocknLock Story

1. What is the material of LocknLock glass tableware?

It is commonly known that “glass” has a very low degree of heat tolerance and is easily breakable; however, there are various types of glass. “Heat resistant glass” is a glass type that is strong in a thermal shock as it contains Silicic acid (SiO₂) and Boracic acid (B₂O₃).

This “Heat resistant glass” is what LOCK&LOCK uses for the material of glass tableware. (*Except products that do not need thermal contact such as fermentation containers) Heat resistant glass goes through a specialized process that supplements the general glass’ weakness. Therefore, it becomes able to withstand high temperatures. Thanks to such feature, it is closely connected to our daily life through various channels including feeding bottles, beakers or bottom glass of microwave. It is also exceedingly popular for a kitchen tableware material.

There is a high possibility to be exposed to heat in the kitchen. It is also more than frequent for tableware to be exposed to use of refrigerator and microwave.Heat resistant glass of LOCK&LOCK is the only fair choice of consumers that has greatly considered the usage environment of kitchenware that is frequently exposed to temperature change.

Heat resistant glass tableware manufactured and distributed by LOCK&LOCK is a safety guaranteed product that has obtained KS Certificate (KS L2424) for Heat Resistant Glass Tableware for Oven and Boiling Water from Korean Standards Association (KSA). It can be used in various environments such as 400℃ of oven, microwave and freezer. It will not break even if you put very hot food you just finished cooking inside. It can be cleaned in boiling water, dishwasher, dish dryer and steam sterilizer.

2. Strong features of LocknLock Heat resistant glass tableware

① Safety that everyone can use

Heat resistant glass has a very low risk of breaking or fragment spreading when there is no deliberate impact given. Both base materials and manufacturing process cause a great cost. However, LOCK&LOCK persists in heat resistant glass usage in order to create a safe kitchen environment where everyone can safely use our products.

② Lightness that lifts a burden on your wrist

Heat resistant glass is at least 10% lighter than tempered glass that has strengthened and thickened the general glass, reducing the weight off of housewives’ wrist.

③ Long-lasting Transparency

General glass often shows efflorescence, a phenomenon that turns murky as it contacts with air when stored for a long time. Heat resistant glass, however, has a low risk of efflorescence when in contact with air as there is a low ratio of sodium oxide. It keeps its transparency for a long time.

Our existing general glass - Nucleation phenomenon - LOCK&LOCK Glass

④ Suitable for Microwave Use

Tempered glass heats up very easily as it absorbs electromagnetic waves more than Heat resistant glass does. On the other hand, Heat resistant glass has a low permittivity, which allows the tableware to be less hot but warms up food better when used in the microwave. This is why bottom glass inside the microwave is made of heat resistant glass.

⑤ Can be used in the oven

Heat resistant glass is made of borosilicate glass that has a strong heat resistance, therefore, holds a great thermal stability. Not only it can be used as an oven cooking container, it can be put in the dishwasher and also be cleaned in boiling water.

3. Heat resistant glass Q&A

① What is the difference between Heat resistant glass & Tempered glass?

“Heat resistant glass” and “Tempered glass” are main special glasses that you can easily see in your daily life and also that are commonly used in tableware. Their features are as different as their manufacturing process.

Features by glass material

Classification Heat resistant glass Tempered glass General glass
Definition Glass that is strong in thermal shock Glass that is strong in physical shock The most commonly used glass such as plate glass or bottle glass
Main ingredients Main ingredients Silicic acid, Boracic acid Silicic acid, Sodium bicarbonate, Lime (Soda lime glass Silicic acid, Sodium bicarbonate, Lime (Soda lime glass
Oven usage X X
Microwave usage X


Strong thermal stability is the feature of Heat resistant glass gained from the addition of the silicic acid and boracic acid. Therefore, it can definitely be used in the microwave, dishwasher, or an oven with a high temperature.

Tempered glass is strong against physical shock as a great compressive stress is created on the surface through a rapid cooling of manufacturing process. It hardly breaks even it if is dropped or falls.

② Why is Heat resistant glass expensive?

Heat resistant glass not only uses costly base material (borosilicate) but also goes through a very complicated manufacturing process, decreasing production efficiency.

③ How do we check the Heat resistant glass materials?

If you are purchasing glass tableware for microwave or oven usage, check the following phrase in the product information.

Heat resistant glass OR
Borosilicate glass

Can be used in the oven OR
Oven Safe