Why Doesn’t Glue Stick to the Inside of the Bottle?

Since we were kids, we used glue to stick things together. Glue is like magical stuff that mends and puts broken things back together. But as we grow older, probably most of us asked why does glue has the ability to stick to most objects, but why doesn’t it stick to the container in which it’s packed? Luckily for you, we are here to answer that question. 

Types of Glue

Before we answer the question, it is essential to note that glue comes in different kinds; most of you might be familiar with a few varieties, but not all of them. The most common type of glue most of us know is regular white glue. This is made of a blend of chemicals commonly known as polymers. White glue is the most common type of glue, and it can be used for semi-porous and porous materials like cardboard, paper, wood, cloth, etc. 

The other type of glue is called yellow glue, and it is commonly sold under the brand name, Titebond. This type of glue is an AR or aliphatic resin glue, and it is thicker and creamier compared to white glue. Yellow glue works well with both semi-porous and porous materials, most especially wooden surfaces.

There are other types of adhesives, such as polyurethane glue, also known as Gorilla glue, hide glue, epoxy, and cyanoacrylate, commonly known as super glue. Some of these adhesives require air or water vapor to set, while others have to undergo chemical changes to activate their tight grip. But nonetheless, none of these types of glue stick to the inside of their bottles.

The Magic and Science of Glue

Obviously, glues are designed to work after they leave their container. Different types of glue adhere in different ways: some contains solvent to retain their liquid form and remain non-sticky within the bottle. 

For example, white glue contains water as the solvent, and it helps keep its thick and liquid form. But, when white glue is squeezed out of the bottle and applied to a surface, it comes into contact with air which evaporates the water that is present in the white glue, thus making it hard. After the water evaporates, only the sticky polymers are left, and they are the ones that are responsible for holding objects together. This process is called mechanical adhesion. 

In short, glue does not normally stick to the inside of the bottle because it needs water vapor or air to adhere or set to another thing firmly. Other types of glue sticks attach to objects when there are chemical reactions present. Since there is only a tiny amount of air or air bubbles inside the glue syringe or bottle, the glue will not have access to enough air to set. Therefore, it will not stick to the inside of the bottle. But, if you happen to leave the bottle’s cap off, the glue could dry up and be useless. 

Why Do Super Glue Tend to Dry Up Within the Tube?

Superglue works a bit differently compared to white glue and other commonly used glues. This is because instead of polymers, super glue contains a chemical called cyanoacrylate. Cyanoacrylates are composed of fast-acting adhesives that tend to have a short shelf life. Super glue bonds things together when it becomes in contact with the water vapor that is present in the air. The moment it happens, the cyanoacrylate molecules start to stiffen and line up, which then becomes absolutely solid and hard while providing fantastic adhesion. This reaction is an example of chemical bonding. This is why super glue is often advised to be stored in a watertight environment so that it would not dry within the bottle. At the same time, white glue needs water to remain non-sticky inside the bottle.