Editing Colloid (section)

=== Destabilization ===
Destabilization can be accomplished by different methods:
*Removal of the electrostatic barrier that prevents aggregation of the particles. This can be accomplished by the addition of salt to a suspension to reduce the [[Debye length|Debye screening length]] (the width of the electrical double layer) of the particles. It is also accomplished by changing the pH of a suspension to effectively neutralise the surface charge of the particles in suspension.<ref name="Israelachvili-2011" /> This removes the repulsive forces that keep colloidal particles separate and allows for aggregation due to van der Waals forces. Minor changes in pH can manifest in significant alteration to the [[zeta potential]]. When the magnitude of the zeta potential lies below a certain threshold, typically around ± 5mV, rapid coagulation or aggregation tends to occur.<ref>{{Cite journal|last1=Bean|first1=Elwood L.|last2=Campbell|first2=Sylvester J.|last3=Anspach|first3=Frederick R.|last4=Ockershausen|first4=Richard W.|last5=Peterman|first5=Charles J.|date=1964|title=Zeta Potential Measurements in the Control of Coagulation Chemical Doses [with Discussion]|url=https://www.jstor.org/stable/41264141|journal=Journal (American Water Works Association)|volume=56|issue=2|pages=214–227|doi=10.1002/j.1551-8833.1964.tb01202.x|jstor=41264141}}</ref>
*Addition of a charged polymer flocculant. Polymer flocculants can bridge individual colloidal particles by attractive electrostatic interactions. For example, negatively charged colloidal silica or clay particles can be flocculated by the addition of a positively charged polymer.
*Addition of non-adsorbed polymers called [[Depletion force|depletants]] that cause aggregation due to entropic effects.

Unstable colloidal suspensions of low-volume fraction form clustered liquid suspensions, wherein individual clusters of particles sediment if they are more dense than the suspension medium, or cream if they are less dense. However, colloidal suspensions of higher-volume fraction form colloidal gels with [[viscoelastic]] properties. Viscoelastic colloidal gels, such as [[bentonite]] and [[toothpaste]], flow like liquids under shear, but maintain their shape when shear is removed. It is for this reason that toothpaste can be squeezed from a toothpaste tube, but stays on the toothbrush after it is applied.