How to Remove Sticky Glasses

Sometimes glass cups stick together if you stack one on top of the other. This often happens because glass expands when washed with hot water, then contracts when it cools. If you want to unscrew glassware, read on for methods of gently twisting, heating, and lubricating the cups!

Table of Contents

Heat use

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Understand how glass reacts to heat. Often glass cups stick together when you stack one on top of the other immediately after washing. Glass expands when heated and contracts when it cools, and this is enough for the cups to stick together in some cases. ^{[1] X Research Source} Don’t worry: you can use this phenomenon to separate cups.

To avoid this problem in the future, you should be careful when stacking cups on top of each other. Wait for the glass to cool first. If you wash the cup with cold water, it’s fine.

Heat the cup outside. This method is risky, so you need to be very careful. The outer cup shrinks around the inner cup, so you need to expand it to loosen the inner cup. Gently heat the outer cup by turning on the hot water to run down for about 1 minute. Luckily, the cup will come loose. If not, you might consider cooling the cup inside by pouring cold water in. ^{[2] X Research Source}

Avoid using ice or boiling water. A sudden change in temperature can cause one of the cups to break and is very dangerous. ^{[3] X Research Source} The glass cup is inherently compressible, so the situation is more risky.

Use force

Try to twist or slope the cups to come apart. A random beaker is rarely perfectly round, so the top cup can only “clip” in two points with the cup below. If the cup moves when it is tilted, it means you are lucky, and it will be much easier to separate the cup

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Be gentle. Remember not to use excessive force. If you twist too hard, you could break one or both of the cups. If the cups come loose all of a sudden, they may slip or fall out of your hand.

Make sure to hold the cups tightly. Dry the cup and hands before removing the cup. If you lose your hand, the cup may fall and shatter!

Consider smashing one of the cups. If you just can’t get the two cups out, perhaps the solution of breaking one cup will keep you from losing both. Place the cup on a stable and easy-to-clean surface, or hold the bottom of the cup in one hand. Use a hammer to tap the rim of the outer cup until it cracks. You run the risk of breaking both cups – but this can be a last-ditch effort.

Remember to clean up any broken pieces of the cup. Safety above all!

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Try blowing between two cups. Sometimes there is a thin layer of water between the two cups that causes them to stick together. Try inserting a straw into the gap between the two cups and blowing into it. Just a little air is enough, but you should blow as much as possible, as the straws are being squashed.

Lubricating the cup

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Apply a thin layer of lubricant. If the cups still won’t loosen, and you’ve tried twisting/increasing the cups to no avail, the next step is to apply a thin layer of lubricant. A little olive or sunflower oil can help. You can also try soap. This is especially effective if the cups are “clamped” to each other instead of tightly glued. ^{[6] X Research Source}

Consider combining the use of oil with the heating method. This can work with sticky cups.
Try WD-40 oil as a last resort. Spray WD-40 oil between the two cups. The oil will spread on its own and will help you remove the two cups fairly easily. Remember to wash the cup thoroughly after separating the cup: WD-40 is toxic to humans.

Pour oil between 2 cups. Tilt the cup slightly up and down so the oil gets into the jam. When you shake the cups, the oil can loosen them enough to separate. Wet the cup to help spread the oil.

Try using a thin straw or blade to push the lubricant between the two cups. Take it easy!

Advice

This works because the top cup shrinks, and the bottom cup expands.

Warning

Do this over the sink to prevent spills.
Don’t immerse delicate cups in hot water, unless you’re sure it’s okay.
Hold the cups low over the sink, and be careful not to drop them. The wet glass beaker is quite slippery.

Things you need

Warm water and cold water
Shallow bowl (optional)
Oil (optional)

Steps