Syneresis And Imbibition

Syneresis And Imbibition

• Syneresis is defied as expression of fluid onto surface of gel structure, this process allows hydrocolloid impression to achieve equilibrium through stress relaxation.
• During syneresis small droplets of exudate are formed on the surface of hydrocolloid and the process occurs irrespective of the humidity of surrounding atmosphere.
• They can be alkaline or acidic depending on the composition of gel.
• It is less in hydrocolloids, i.e. alginate and agar which contain a high concentration of dispersed medium.
• Gel shrinks during syneresis and alters original dimension of impression. So the cast which is made get altered in its dimensions.

Imbibition:

• Imbibition is defined as the process of water sorption.
• If a hydrocolloid gel is placed in water it will absorb water by the process known as imbibition.
• Gel gets swelled during imbibition and thereby alters the original dimensions. So the cast which is made from that will be smaller in dimension.
• Irreversible hydrocolloids will continue to undergo imbibitions if they are placed under the water. They imbibe until the water content is much greater than that of the original gel.

Importance: Syneresis and imbibition can result in dimensional changes and therefore inaccurate cast. To avoid this, hydrocolloid impression should be poured immediately.