The bonded hair extension technique typically relies on adhesives to secure the extension to your hair. Adhesive bond "glues" are actually primarily keratin or wax based products with the keratin based formulas being the strongest. They will generally become harder than their wax based counterpart.
The wax based product comes in a variety of "hold" types with the most popular being regular or medium hard hold. The great thing about fusion adhesives is that they don't require acetone (which can be damaging to the hair) to remove the hair extensions. Medium hard hold wax adhesives can last up-to 3 months, whereas keratin adhesives are harder and can go strong for up-to 6 months.
Liquid Bonding or Cold Bonding
Liquid bonding comes in two types. The more upscale products generally have to be purchased through a specialty provider or internet. They tend to last longer and do not break down as easily as their rubberized counterparts. The rubberized adhesives can be found at virtually an beauty supply store and are generally meant for temporary extensions because they breakdown in the presence of water and oils and last only a few days.
Thermal Head, Fusion or Modulation Bonding
These types of adhesives are typically used with strand bond extensions. The bonding adhesive is a wax-based product that is formulated to hold up in the presence of mild temperatures. With this technique, a thermal heat appliance is used to melt the adhesive. As it cools, it quickly hardens into a firm, flexible bond. In order to remove the bond, additional heat is required.
The great thing about thermal bonding adhesives is that they can withstand normal styling. They generally do not soften in the presence of most hair care products.
Please consult a licensed professional before gluing stuff to your hair.